WO1999046602A1 - Optical translation measurement - Google Patents

Optical translation measurement Download PDF

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Publication number
WO1999046602A1
WO1999046602A1 PCT/IL1998/000113 IL9800113W WO9946602A1 WO 1999046602 A1 WO1999046602 A1 WO 1999046602A1 IL 9800113 W IL9800113 W IL 9800113W WO 9946602 A1 WO9946602 A1 WO 9946602A1
Authority
WO
WIPO (PCT)
Prior art keywords
radiation
reflected
detector
determining
relative motion
Prior art date
Application number
PCT/IL1998/000113
Other languages
French (fr)
Inventor
Opher Kinrot
Uri Kinrot
Gilad Lederer
Original Assignee
Gou Lite Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Gou Lite Ltd. filed Critical Gou Lite Ltd.
Priority to AU66337/98A priority Critical patent/AU6633798A/en
Priority to PCT/IL1998/000113 priority patent/WO1999046602A1/en
Priority to US09/623,652 priority patent/US6424407B1/en
Priority to IL12430098A priority patent/IL124300A0/en
Priority to IL12543198A priority patent/IL125431A0/en
Priority to IL12665698A priority patent/IL126656A0/en
Priority to US09/264,410 priority patent/US6330057B1/en
Priority to US09/264,409 priority patent/US6452683B1/en
Priority to US09/264,411 priority patent/US6246482B1/en
Priority to CNB998002534A priority patent/CN1144063C/en
Priority to EP99200687A priority patent/EP0947833B1/en
Priority to JP54555899A priority patent/JP3321468B2/en
Priority to IL13830499A priority patent/IL138304A0/en
Priority to CA002322874A priority patent/CA2322874A1/en
Priority to EP99200686A priority patent/EP0942286B1/en
Priority to DE69900565T priority patent/DE69900565T2/en
Priority to EP99907827A priority patent/EP1062519A2/en
Priority to AU27439/99A priority patent/AU750415B2/en
Priority to DE69904254T priority patent/DE69904254T2/en
Priority to CNA2003101027889A priority patent/CN1548963A/en
Priority to MXPA00009038A priority patent/MXPA00009038A/en
Priority to EP99200685A priority patent/EP0942285B1/en
Priority to PCT/IL1999/000137 priority patent/WO1999046603A1/en
Priority to NZ506914A priority patent/NZ506914A/en
Priority to DE69900444T priority patent/DE69900444T2/en
Publication of WO1999046602A1 publication Critical patent/WO1999046602A1/en
Priority to US10/200,000 priority patent/US6741335B2/en

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Classifications

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    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/0304—Detection arrangements using opto-electronic means
    • G06F3/0317—Detection arrangements using opto-electronic means in co-operation with a patterned surface, e.g. absolute position or relative movement detection for an optical mouse or pen positioned with respect to a coded surface
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02041—Interferometers characterised by particular imaging or detection techniques
    • G01B9/02045—Interferometers characterised by particular imaging or detection techniques using the Doppler effect
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02049—Interferometers characterised by particular mechanical design details
    • G01B9/02051—Integrated design, e.g. on-chip or monolithic
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02055—Reduction or prevention of errors; Testing; Calibration
    • G01B9/02056—Passive reduction of errors
    • G01B9/02057—Passive reduction of errors by using common path configuration, i.e. reference and object path almost entirely overlapping
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02055—Reduction or prevention of errors; Testing; Calibration
    • G01B9/0207—Error reduction by correction of the measurement signal based on independently determined error sources, e.g. using a reference interferometer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/36—Devices characterised by the use of optical means, e.g. using infrared, visible, or ultraviolet light
    • G01P3/366—Devices characterised by the use of optical means, e.g. using infrared, visible, or ultraviolet light by using diffraction of light
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/64—Devices characterised by the determination of the time taken to traverse a fixed distance
    • G01P3/80—Devices characterised by the determination of the time taken to traverse a fixed distance using auto-correlation or cross-correlation detection means
    • G01P3/806—Devices characterised by the determination of the time taken to traverse a fixed distance using auto-correlation or cross-correlation detection means in devices of the type to be classified in G01P3/68
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/50—Systems of measurement based on relative movement of target
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G01S7/4811—Constructional features, e.g. arrangements of optical elements common to transmitter and receiver
    • G—PHYSICS
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    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/0304—Detection arrangements using opto-electronic means
    • G06F3/0312—Detection arrangements using opto-electronic means for tracking the rotation of a spherical or circular member, e.g. optical rotary encoders used in mice or trackballs using a tracking ball or in mouse scroll wheels
    • G—PHYSICS
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    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/033—Pointing devices displaced or positioned by the user, e.g. mice, trackballs, pens or joysticks; Accessories therefor
    • G06F3/0354—Pointing devices displaced or positioned by the user, e.g. mice, trackballs, pens or joysticks; Accessories therefor with detection of 2D relative movements between the device, or an operating part thereof, and a plane or surface, e.g. 2D mice, trackballs, pens or pucks
    • G06F3/03543—Mice or pucks
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/033—Pointing devices displaced or positioned by the user, e.g. mice, trackballs, pens or joysticks; Accessories therefor
    • G06F3/0354—Pointing devices displaced or positioned by the user, e.g. mice, trackballs, pens or joysticks; Accessories therefor with detection of 2D relative movements between the device, or an operating part thereof, and a plane or surface, e.g. 2D mice, trackballs, pens or pucks
    • G06F3/03545—Pens or stylus
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/033—Pointing devices displaced or positioned by the user, e.g. mice, trackballs, pens or joysticks; Accessories therefor
    • G06F3/0354—Pointing devices displaced or positioned by the user, e.g. mice, trackballs, pens or joysticks; Accessories therefor with detection of 2D relative movements between the device, or an operating part thereof, and a plane or surface, e.g. 2D mice, trackballs, pens or pucks
    • G06F3/03547—Touch pads, in which fingers can move on a surface
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/033—Pointing devices displaced or positioned by the user, e.g. mice, trackballs, pens or joysticks; Accessories therefor
    • G06F3/0354—Pointing devices displaced or positioned by the user, e.g. mice, trackballs, pens or joysticks; Accessories therefor with detection of 2D relative movements between the device, or an operating part thereof, and a plane or surface, e.g. 2D mice, trackballs, pens or pucks
    • G06F3/03548—Sliders, in which the moving part moves in a plane
    • G—PHYSICS
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    • G06F—ELECTRIC DIGITAL DATA PROCESSING
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    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/042—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by opto-electronic means
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/042—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by opto-electronic means
    • G06F3/0421—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by opto-electronic means by interrupting or reflecting a light beam, e.g. optical touch-screen
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B2290/00—Aspects of interferometers not specifically covered by any group under G01B9/02
    • G01B2290/30—Grating as beam-splitter
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    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2203/00—Indexing scheme relating to G06F3/00 - G06F3/048
    • G06F2203/033—Indexing scheme relating to G06F3/033
    • G06F2203/0338—Fingerprint track pad, i.e. fingerprint sensor used as pointing device tracking the fingertip image

Definitions

  • Speckle Velocimetry methods are generally based on the following operational principles:
  • speckle size the typical average or mean distance for a significant change in intensity
  • the typical "speckle” size depends primarily on the light wavelength, on the distance between the object and the speckle image plane and on the size of the illuminated area. • If the object moves relative to the plane in which the speckle image is observed, the speckle image will move as well, at essentially the same transverse velocity. (The speckle image will also change since some scatterers leave the illuminated area and some enter it).
  • the speckle image is passed through a structure comprising a series of alternating clear and opaque or reflecting lines such that the speckle image is modulated.
  • This structure is generally a pure transmission grating, and, ideally is placed close to the detector for maximum contrast.
  • the detector translates the intensity of the light that pass through the structure to an electrical signal which is a function of the intensity (commonly a linear function).
  • US Patent 3,856,403 to Maughmer, et al. also attempts to avoid the directional ambiguity by providing a moving grating. It provides a bias for the velocity measurement by moving the grating at a velocity higher then the maximum expected relative velocity between the surface and the velocimeter. The frequency shift reduces the effect of changes in the total light intensity (DC and low-frequency component), thus increasing the measurement dynamic range and accuracy.
  • PCT publication WO 86/06845 to Gardner, et al. describes a system designed to reduce the amplitude of DC and low frequency signal components of the detector signal by subtracting a reference sample of the light from the source from the speckle detector signal.
  • the reference signal is proportional to the total light intensity on the detector, reducing or eliminating the influence of the total intensity variations on the measurement.
  • SV Velocimetry
  • a coherent light source is split into two beams.
  • One beam (a "primary" beam) illuminates an object whose velocity is to be measured.
  • the other beam (a "reference” beam) is reflected from a reference element, usually a mirror, which is part of the measurement system.
  • the light reflected from the object and from the reference element are recombined (usually by the same beam splitter) and directed to a light-sensitive detector.
  • EQEI includes two oscillating terms.
  • One of these terms oscillates at about twice the optical frequency, and is averaged to zero by the detector time-constant.
  • the second term oscillates with frequency ⁇ - ⁇ i , i.e.- with the same frequency as the frequency shift due to the Doppler effect.
  • the detector output signal contains an oscillating component with frequency indicative of the measured velocity.
  • US patent 5,588,437 to Byrne, et al. describes a system in which a laser light source illuminates a biological tissue. Light reflected from the skin surface serves as a reference beam for homodyne detection of light that is reflected from blood flowing beneath the skin. Thus, the skin acts as a diffused beam splitter close to the measured object.
  • An advantage of using the skin as a beam splitter is that the overall movement of the body does not effect the measurement. Only the relative velocity between the blood and the skin is measured.
  • Optical Coherence Tomography a low-coherence light source (“white light”) is directed and focused to a volume to be sampled. A portion of the light from the source is diverted to a reference path using a beam-splitter. The reference path optical length is controllable. Light reflected from the source and light from the reference path are recombined using a beam-splitter (conveniently the same one as used to split the source light). A light- sensitive detector measures the intensity of the recombined light.
  • the source coherence length is very short, so only the light reflected from a small volume centered at the same optical distance from the source as that of the reference light coherently interferes with the reference light.
  • a paper by Izatt et al. entitled “In Vivo Bidirectional Color Doppler Flow Imaging of Picoliter Blood Volumes Using Optical Coherence Tomography” (Optics Letters 22, p.1439, 1997) describes an optical-fiber-based OCT with a velocity mapping capability.
  • An optical- fiber beam-splitter is used to separate the light paths before the reflection from the sample in the primary path and from the mirror in the reference path and combine the reflections in the opposite direction.
  • a paper by Suhara et al. entitled “Monolithic Integrated-Optic Position/Displacement Sensor Using Waveguide Gratings and QW-DFB Laser” (IEEE Photon. Technol. Lett.
  • the present invention in its broadest form provides an Optical Translation Measurement (OTM) method and device, capable of providing information indicative of the amount and optionally the direction of relative translation between the device and an adjacent object.
  • OTM Optical Translation Measurement
  • the object is at least partly rough and is closely spaced from the device.
  • the terms "rough” or “diffuse” mean optically irregular or non-uniform.
  • the object may have a diffuse opaque or semi-transparent surface such as a paper. This specification deals mainly with determining the translation or velocity of such diffuse surfaces.
  • many of the methods of the invention may also be applicable to determination of translation of other types of objects such as small scattering particles, possibly suspended in fluid. Translation of the object means that its rotation in space may be neglected.
  • the invention provides heterodyne or homodyne detection of non-Doppler, non-speckle-image signals derived from changes in the phase and/or the amplitude of reflection from an optically irregular surface.
  • the invention provides a system in which a reflector which reflects part of the incident light is placed next to the surface whose motion is to be measured.
  • the reflector provides a local oscillator signal which is inherently coherent with the light which is reflected from the surface.
  • This aspect of the invention is applicable to both Doppler and non-Doppler methods of motion detection.
  • the partial reflector is an apertured reflector in which the illumination of the surface whose motion is measured pass through the aperture.
  • the partial reflector covers a portion of the measured surface and has a substantial amount of transmission.
  • the reflections from the surface pass through the partial reflector.
  • a combination of apertureing and partial transmission is often useful, especially in preferred embodiments of the invention which utilize the third aspect of the invention.
  • a non-symmetrical transmission pattern is provided to aid in determining the direction of motion of the surface.
  • the phase shift may also be a static phase shift.
  • this static phase shift is accompanied by a change in polarization of one of the beams (or a part of the energy in the beam).
  • the direction of motion is determined by a measurement of the phase change and more particularly by measurement of the sign of the phase change.
  • the phase of a portion of a beam whose phase is not changed is compared with the phase of a portion which is changed, to determine the direction of motion.
  • a sixth aspect of the invention provides for simultaneous two or three dimensional translation detection using a single illuminating beam and a single reflector to provide local oscillator reference beams.
  • the signal generated by a single detector is used to determine the translation in two dimensions.
  • a surface is illuminated with a preferably periodically spatially varying illumination and a spatial filter is provided such that the illumination is reflected from the surface such that substantially only a single spatial frequency of the reflected radiation is incident on the detector.
  • the spatial filter comprises a lens having a focal point and a pinhole which is placed at the focal point of the lens.
  • the illumination of the surface is collimated and the spatial filter filters the reflected illumination such that only radiation reflected from the surface substantially in a single direction is incident on the detector.
  • a device includes a light source, a grating, a spatial filter, a photo-detector, and signal processing electronics.
  • the light source provides at least partially coherent radiation, which is directed toward the surface.
  • An optical grating is placed between the surface and the light source, preferably close to the surface.
  • the light reflected from the surface interferes with the light that is reflected from the grating itself.
  • the detector signal includes an oscillating component, that is representative of the surface translation relative to the optical device. The interference may take place with the normal reflection from the grating or with light diffracted at any of the grating orders. Most preferably, the light passes through a spatial filter prior to detection by the detector.
  • Two dimensional translation measurement may be achieved by using orthogonal reflection orders from a two- dimensional grating or by utilizing two separate gratings for the two directions.
  • a third dimension may be deduced by vector calculation of the translations measured in two different orders at the same axis (e.g.- 0 and 1, 1 and 2, -1 and 1, etc.), or without an additional detector, simultaneously using different signal analysis techniques on the same signal.
  • Optional detection of the direction of translation is preferably achieved by modulating the grating position to provide a frequency offset.
  • a varying optical path length between the grating and the surface introduces the frequency offset.
  • an asymmetric pattern for the grating transmission and appropriate signal manipulation/processing may be used.
  • the direction may be determined by other means.
  • the method and device of the invention are applicable to a wide range of applications that require measurement of translation.
  • One such application is a "padless optical mouse", that can effectively control a cursor movement by moving the mouse across an optically diffuse surface such as a paper or a desk-top.
  • Another exemplary application for the invention is for a "touch-point”, that translates finger movement over a device aperture to control a cursor or any other translation or velocity controlled entity.
  • the measurement apparatus comprises a light source for providing at least partially coherent radiation.
  • the source radiation is directed toward an optical one-dimensional or two-dimensional grating, which is preferably close to the reference surface.
  • the spatial filter may simply be a lens with a pinhole positioned at it's focal point. Any translation of the surface does not change the relative phases of the light integrated by the spatial filter.
  • the local oscillator formed by the reflection or the diffraction from the reflector or grating is also perfectly collimated, so that it can also be passed through the spatial filter (the spatial filter is positioned such that the image of the source falls on or within the pinhole). This forces a single interference fringe on the detector. No limitations are imposed (with regard to spatial filtering) on the spacing between the reflector and the surface.
  • the measurement may be termed "speckle-free"
  • the detector itself is small enough, it may serve as an integral part of the spatial filter and a pin-hole is not required.
  • the requirements of unchanged relative phases and single interference fringe with the local oscillator at the detector can be fulfilled in a multitude of optically equivalent ways.
  • the requirement may be established using a single converging lens positioned before or after the reflection of the light from the reflector.
  • the lens and the reflector can be combined in a single optical device.
  • a collimating lens may be positioned between the beamsplitter and the surface (i.e.- only light to and from the surface pass through this lens).
  • Non-ideal spatial filtering (as when the pin hole is too large, or when it is out of focus for either the reflection from the surface or the local oscillator or both), results in deterioration of the signal and possibly the addition of noise to the measurement.
  • both the surface illumination and the reference light are provided using a single optical element, preferably a grating.
  • the surface and reference light share a single optical path through all of the optical elements in the device.
  • the spatial amplitude and/or phase modulation, imposed on the light reaching the surface by the grating provide additional means for measuring the surface's translation. In particular, tangential translation can be measured even for specular reflection from the grating, where no Doppler shift exists, and identification of the direction of motion can also be achieved.
  • the object is partially reflecting, part of the incident radiation is reflected or diffracted by the object towards a detector, as a reference radiation and detection of the radiation is coherent, utilizing said reference radiation.
  • a method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface with incident radiation such that the radiation is reflected from portions of the surface towards a detector; placing a partially reflecting object, which is part of the measuring device, adjacent to the surface, wherein part of the incident radiation is reflected or diffracted by the object towards the detector, as a reference radiation; coherently detecting the radiation reflected from the surface utilizing the reference radiation, such that the detector generates a signal; and determining the relative motion of the surface parallel to the surface, from the detected signal.
  • placing an object adjacent to the surface comprises placing a grating adjacent to the surface.
  • the detected radiation is at least partly coherent.
  • the object and the surface are situated within a distance which is less than the coherence length of the radiation which reaches the detector.
  • the radiation reflected from the surface is frequency shifted from that of the radiation reflected from or diffracted by the object and determining the motion comprises determining the motion based on the frequency shift.
  • determining the motion comprises determining variations in the amplitude of the signal with position.
  • the motion is determined from zero crossings of the detected signal.
  • the method comprises: varying the phase between the radiation reflected from or diffracted by the object and at least a portion of the radiation reflected from the surface.
  • a method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface with incident radiation such that radiation is reflected from portions of the surface and such that radiation is reflected from or diffracted by the object toward a detector; placing a partially reflecting object, which is part of the measuring device, adjacent to the surface, wherein part of the incident radiation is reflected or diffracted by the object towards the detector, as a reference radiation; coherently detecting the radiation reflected from the surface utilizing the radiation reflected from or diffracted by the object as a local oscillator to form a signal; determining the relative motion of the surface from the signal; varying the phase of the radiation reflected from or diffracted by the object with respect to that reflected from the surface; and determining the direction of relative motion parallel to the surface based on a characteristic of the signal caused by said varying relative phase.
  • varying the phase comprises periodically varying the phase.
  • determining the direction of relative motion comprises determining the direction of relative motion based on a characteristic of the signal caused by said varying relative phase.
  • a method includes dividing the radiation that is reflected from the surface into a first radiation having a first phase and a second radiation having a second phase.
  • the first and second radiations have different polarizations.
  • dividing comprises passing the radiation incident on the surface through a birefringent material.
  • the method includes passing the radiation reflected from the surface through the birefringent material.
  • the method includes placing the birefringent material between the object and the surface.
  • the method includes determining the direction of translation from the sign of the phase difference between the first and second radiations.
  • the method includes determining the magnitude and direction of the translation utilizing two detectors which produce different signals.
  • a method for determining the relative motion of a surface with respect to a measurement device comprising: placing an apertured reflector, which is part of the measurement device, adjacent to the surface; illuminating the surface with incident radiation such that radiation is reflected from portions of the surface and such that radiation is reflected from or diffracted by the apertured reflector toward the detector; coherently detecting the radiation reflected from the surface utilizing the radiation reflected from or diffracted by the apertured reflector as a local oscillator to form a signal; determining the relative motion of the surface perpendicular to and parallel to the apertured reflector from the signal.
  • coherently detecting comprises: detecting amplitude or phase variations of the reflected radiation; and detecting a frequency shift of the reflected radiation; and determining the relative motion comprises: measuring relative motion of the surface in a direction parallel to the apertured reflector responsive to at least one of the detected amplitude or phase variations; and measuring relative motion of the surface in a direction perpendicular to the surface of the apertured reflector responsive to the detected frequency shift.
  • the method comprises periodically moving the apertured reflector surface in a direction perpendicular to its surface to add a periodic phase shift to the radiation reflected therefrom and utilizing said phase shift to measure the motion of the surface.
  • a method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface, from a source, with incident radiation such that radiation is reflected from portions of the surface toward the detector; spatially filtering the reflected radiation such that the phase of the optical radiation exiting the spatial filter from a given scatterer on the surface is substantially constant or linearly related to the translation of the surface; generating a signal by the detector responsive to the radiation incident on the detector; and determining the relative motion of the surface from the signal.
  • illuminating comprises illuminating the surface with spatially varying radiation.
  • illuminating the surface comprises illuminating the surface through an apertured reflector placed adjacent to the surface which reflects or diffracts radiation to the detector.
  • generating a signal comprises coherent detection of the radiation reflected from the surface utilizing the radiation reflected or diffracted from the apertured reflector.
  • determining the relative motion comprises utilizing a Doppler shift of the reflected radiation.
  • illumination of the surface is substantially collimated and the spatial filter filters the reflected illumination such that substantially only a single spatial frequency of the reflected radiation is incident on the detector.
  • illumination of the surface is substantially collimated and spatial filtering filters the reflected illumination such that only radiation reflected from the surface substantially in a single direction is incident on the detector.
  • spatial filtering comprises focusing the reflected radiation with a lens and placing a pinhole at an image of the source.
  • a method for determining the relative motion of a surface with respect to a measurement device comprising: placing an object, having at least a quasi-continuous transmission function, adjacent to the surface; illuminating the surface with incident radiation such that radiation is reflected from portions of the surface toward a detector; detecting the radiation reflected from the surface utilizing the detector to generate a signal; and determining the relative motion of the surface from the signal.
  • the object has an asymmetric transmission function and determining the relative motion comprises determining the direction of motion based on the detected signal.
  • radiation is reflected from or diffracted by the object toward the detector and detection is coherent detection utilizing the radiation reflected from or diffracted by the apertured reflector as a local oscillator to form a signal.
  • a method for determining the relative motion of a surface with respect to a measuring device comprising: illuminating the surface with incident visible or infrared radiation such that radiation is reflected from the surface to illuminate a detector with radiation which is not an image of a point on or a portion of the surface; simultaneously illuminating the detector with reference radiation derived from said incident radiation; coherently detecting the reflected illumination of the detector utilizing said reference radiation such that the detector generates a signal; determining the relative motion of the surface parallel to the surface, based on variations of the signal with time.
  • the incident radiation is at a given wavelength and the reference radiation is at the same wavelength such that the coherent detection is homodyne detection.
  • the method includes spatially varying the illumination of the surface.
  • spatially varying the illumination of the surface comprises illuminating the surface through an apertured reflector.
  • spatially varying the illumination of the surface comprises illuminating the surface through a transmission grating having spatially varying periodic transmission.
  • spatially varying the illumination of the surface comprises: illuminating the surface through a grating which specularly reflects a portion of the radiation incident upon it toward the detector to form said reference radiation.
  • a method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface with visible or infrared radiation such that radiation is reflected from portions of the surface toward a detector; coherently detecting the radiation reflected from the surface; and determining the relative motion of the surface, in a direction parallel to the surface, from a characteristic of the signal based on a Doppler shift of the reflection reflected from the surface.
  • the method includes placing an apertured reflector adjacent to the surface, wherein said coherent detection utilizes radiation reflected from or diffracted toward the detector from the apertured reflector as a local oscillator.
  • the apertured reflector is a grating and radiation diffracted by the grating is used in determining the motion.
  • the illumination is perpendicularly incident on the surface.
  • the surface is an optically diffusely reflecting surface.
  • the surface has no markings indicating position.
  • an optical mouse comprising: a housing having an aperture facing a surface; and an optical motion detector which views the surface through the aperture, wherein the optical motion detector utilizes the method of the invention to determine the translation of the housing with respect to the surface.
  • a touch point for use as a control device comprising: a housing having an aperture; and an optical detector which determines the motion of a finger which is translated across the aperture.
  • the touch point utilizes the method of the invention to determine the translation.
  • a pointer device comprising: a first touch point according to the invention and circuitry which moves a pointer responsive thereto; and a second touch point according to the invention and circuitry which causes scrolling responsive thereto.
  • a combination mouse/touch point for use as a pointer for a computer comprising: a housing having an aperture; an optical detector which determines the motion of an object which is translated across the aperture; and means for determining whether the aperture is upward or downward facing.
  • a scanner for reading a document by movement of the scanner over the document comprising: an optical reading head which detects patterns on the surface of the document; and an optical detector which determines the motion of the scanner as it is translated across the surface of the document, wherein the optical detector utilizes the method of the invention to determine the translation.
  • an encoder comprising: an optically diffusely reflecting surface; and an optical detector having relative motion with respect to the surface, wherein the optical detector measures relative motion with respect to the surface without utilizing markings on the surface.
  • a virtual pen comprising an encoder according to the invention and circuitry which translates said measured relative motion into written or graphical data.
  • the virtual pen utilizes the method of the invention.
  • a document scanner comprising a device for moving a sheet of paper according to the invention, a reading head which reads information from the paper and a memory which stores the information in memory locations responsive to the measurement of movement of the paper.
  • a printing machine comprising a device for moving a sheet of paper according to the invention, a memory which contains information to be printed on the sheet of paper and a printing head which prints the information responsive to the measurement of movement of the paper.
  • a facsimile machine comprising a scanner according to the invention, a printer according to the invention or both.
  • a method for determining the direction of relative motion of a surface with respect to a measurement device comprising: illuminating the surface with incident radiation such that radiation is reflected from portions of the surface toward a detector; placing an object, having an asymetric transmission function, adjacent to the detector; detecting the radiation reflected from the surface utilizing the detector to generate a signal; and determining the direction of relative motion of the surface from the signal.
  • Fig. 2 is a graph of a grating transmission function, in accordance with a prefe ⁇ ed embodiment of the invention
  • Figs. 3A, 3B and 3C are schematic representations of prefe ⁇ ed embodiments of integrated motion transducers, in accordance with prefe ⁇ ed embodiments of the invention.
  • Fig. 4 is a schematic diagram of an optical mouse in accordance with a prefe ⁇ ed embodiment of the invention
  • Figs. 5 A and 5B are schematic diagrams of a mouse/finger translation measurement device, in accordance with a prefe ⁇ ed embodiment of the invention
  • Fig. 6 is a schematic diagram of a scanning pen in accordance with a prefe ⁇ ed embodiment of the invention.
  • Fig. 7 is a diagram of a rotary encoder, in accordance with a prefe ⁇ ed embodiment of the invention.
  • Fig. 8 is a schematic diagram of a fiber-optic-based translation measurement device, in accordance with a preferred embodiment of the invention.
  • Fig. 9 is a simplified and generalized block diagram of electronic circuitry, suitable for use in prefe ⁇ ed embodiments of the invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
  • Fig. 1 shows apparatus 10 for the measurement of the translation of a surface 12, in accordance with a preferred embodiment of the invention.
  • Apparatus 10 comprises a source of at least partially coherent, preferably collimated optical radiation 14, such as a laser.
  • the laser is a diode laser, for example a low power infra-red laser. While other wavelengths can be used, an infra-red laser is preferred since it results in eye-safe operation.
  • the source is preferably collimated. However, a non-collimated source may be used if compensation as described below is used. While it is desirable to use a collimated source from power considerations, the collimation need not be particularly good.
  • Fig. 1 the light is seen as being incident on the surface from an angle; however, it is possible for the light to be incident at the normal to grating 16. Moreover, while Fig. 1 shows the incident light angle equal to the detection angle, such that light reflected from the grating (or zeroth order diffraction) is used for the local oscillator, first or higher order diffraction by the grating can be effectively used. Zero order has the advantages that it is wavelength independent (stability of the wavelength is not important).
  • the incident light can be pulsed or continuous.
  • light diffracted at the -1 and +1 orders are indicated by reference numbers 19 and 21 respectively. Light which is scattered by the surface is indicated by reference number 17.
  • speckle- free, coherent detection is used to determine tangential motion.
  • Such detection results in an intrinsic amplification of the signal used for measurement resulting in a high dynamic range.
  • the reference local oscillator field for the coherent detection is provided by reflections from grating 16, placed close to the moving surface.
  • the interference of the reflections from the grating and the moving surface on the detector give rise to a translation dependent oscillating signal.
  • the incorporation of a near-surface reflection from a grating as the origin of the local oscillator field may give multiple advantages, including at least some of the following: 1.
  • the grating is a single element that combines the roles of a beam splitter and a mirror in a coherent homodyne/heterodyne detection optical setup, thus making the optical system simple, robust and with few alignment requirements.
  • the grating causes spatially periodic intensity and/or phase modulation of the illumination reflected from the surface, if the surface is placed within the near field of the grating. This enables detection of translation using the specular (zeroth order) reflection as the reference wave.
  • High order reflections ( ⁇ l st , ⁇ 2 nc % etc.) serve as local oscillator fields for higher resolution detection of the surface's translation.
  • a translation dependent phase shift between the reference and surface waves at non-specular reflection orders produce oscillations representative of the translation.
  • Translation detection can be frequency biased by periodic shifting of the grating position (e.g. sawtooth modulation), enabling determination of direction as well as magnitude of the translation.
  • periodic shifting of the grating position e.g. sawtooth modulation
  • Measurement at different grating orders provides different components of the translation or velocity vector of the surface.
  • translation along the axis perpendicular to the grating can be measured independently of translation in the other directions. This allows for three dimensional translation measurement by adding the measurement or the calculation of the axial component for two measurements performed for the same transverse axis but in different grating orders.
  • Asymmetric grating transmission functions enable direction detection in all reflected orders, using appropriate signal manipulation/analysis.
  • the spacing is assumed to be near field. This requirement is relaxed for the cases where it is not essential.
  • Plane-wave illumination by the light source over the grating area is assumed (i.e.- a collimated beam), but is not strictly necessary provided, for example, the non-collimation is compensated in another part of the system (e.g.- the spatial filter). It is assumed for simplicity that the incident light is pe ⁇ endicular to the grating (and not as shown in Fig. 1). Oblique incident light (in the direction of the grating lines and/or pe ⁇ endicular to it) gives substantially the same results, with shifted reflection angles.
  • a spatial filter in front of the detector is preferably comprised of focusing lens 18 and narrow pinhole 20 at the focal point of the lens.
  • Such a spatial filter is preferably adjusted to select only a single spatial frequency component to reach the detector.
  • the pinhole can be replaced by a single-mode optical fiber, having a similar core diameter and leading the light to a remote detector.
  • the spatial filter is aligned such that one of the diffraction orders reaches the detector, and serves as the local oscillator for homodyne detection of the reflected radiation, or for heterodyne detection as described below.
  • the local oscillator field is given by:
  • E LO(t) E n cos ( ⁇ 0 t + ⁇ n) ( )
  • the reflected field from the moving surface in the same direction as the n-th diffraction order is represented by an integral over the illuminated surface area of independent reflections from the surface.
  • the ratio of the strength of the local oscillator field and of the reflected field is intrinsically large, since the reflection from the grating is directed only to specific narrow orders and the reflection from the diffuse surface is scattered over a broad angle.
  • Translation measurement utilizing the spatial transmission modulation is possible even if the third term alone is present, i.e., when the light reflected from the surface is not combined with a reference reflected or diffracted from the grating. This may be achieved (if desired) by selecting an angle which lies between grating orders. It does have the advantage of significantly relaxed alignment constrains (it is only required to be in the focal plane of the spatial filter), but will generally be less accurate and with a low signal-to-noise ratio.
  • the local oscillator field serves as a very strong amplifier in the first stage of signal detection. In this respect it is strongly prefe ⁇ ed to keep the local oscillator field as noise-free as possible, since its noise transfers to the detected signal directly.
  • I s (t) E n cos( ⁇ 0 t + ⁇ n )E r (t) (9)
  • the grating has a period ⁇ .
  • I s (t) I n c ⁇ Jdxcos(2 ⁇ x/ ⁇ + 2 ⁇ p(t)/ ⁇ + ⁇ )r(x)cos(2 ⁇ np(t) / ⁇ + ⁇ n (x) - ⁇ n ) (13) ⁇ ⁇ -p(t)
  • the intensity I(t) and phase ⁇ (t) result from integrals over random variables co ⁇ esponding to the amplitude and phase reflection of the diffuse surface at a spatial frequency 1/ ⁇ .
  • the contribution will come from grain boundaries, while for diffuse surfaces having small particle sizes there will be strong contributions for all spatial frequencies up to 1/d, where d is the average particle size.
  • the measured signal's amplitude and phase are slowly varying statistical ensemble sums.
  • the relative accuracy of the measurement is proportional to ⁇ /L, L being the illuminated grating size.
  • the spacing between the surface and the grating should preferably be smaller than both the near field distance, « ⁇ *2/4 ⁇ , and the coherence length of the light reaching the detector, « ⁇ 2 / ⁇ .
  • Equation (19) neglects a slowly varying term that adds to the average detector signal (the "DC" component).
  • n>l the measured signal will oscillate according to np(t)/ ⁇ .
  • the c term amount to oscillations in two side bands around the CQ oscillations as in amplitude modulation of a higher frequency signal.
  • a transmission function for the grating such that co»c ⁇ even in the near field can be used.
  • the ratio between the carrier frequency and the amplitude modulation frequency can be made large, improving the measurement accuracy as well as allowing for detection of the direction of translation. Also, using specular reflection from the grating as a local oscillator enables a clear distinction to be made between the transverse translation component (indicated by the amplitude modulation) and the axial translation component (indicated by the phase or frequency shift of the carrier frequency).
  • phase shifting may be combined with an asymmetric transmission pattern of the grating (e.g.- sawtooth pattern) for the pu ⁇ ose of transverse translation direction detection.
  • the grating may be displaced for direction detection in the two dimensions.
  • two quasi- plane waves are selected for detection by the detector.
  • One of these waves is the result of the nth order diffraction from the grating.
  • the second plane wave is generated by the selection of one plane wave (by the spatial filter) from the reflections from the surface.
  • direction may be determined by applying an additional phase shift between the reference (local oscillator) field and the reflected field.
  • This additional phase shift can be manifested, for example, by moving the grating towards or away from the surface. This movement does not change the phase of the field incident upon the surface, so that the reflected field is identical to that given above.
  • the local oscillator field acquires an additional phase shift due to this translation that depends on the grating displacement d(t).
  • saw-tooth includes such non-ideal variations.
  • An alternative way of introducing a periodic phase shift between the local oscillator field and the field reflected from the surface is to modulate the optical path length between the grating and the surface. This is preferably achieved by a transparent piezo-electric element mounted between the grating and the surface.
  • An alternative methodology to break the symmetry between positive and negative relative translation, so that the translation direction can be detected, is to use an asymmetric function for the transmission (amplitude and/or phase) function of the grating.
  • the formalism is developed for an amplitude grating. For simplicity, assume that the grating is large compared to the line spacing along the translation axis and that k point scatterers are illuminated through the grating. Scatterers entering or leaving the illuminated area are neglected
  • the magnitude, and more importantly, the sign of the translation velocity can be derived from the ratio between the first and second time-derivatives of the detector signal. If the velocity cannot be assumed to be constant during the direction-decision integration time, then the derivatives may be performed with respect to the measured translation (which is known from the zero-crossing or from another detector with higher accuracy operated in parallel). If only the direction is required (and not the velocity magnitude), it is sufficient to check if the first and second derivatives carry the same sign (one direction) or not (opposite direction). A simple XOR (exclusive OR) operation after sign-detection of the derivatives will be "1" if the sign of ⁇ is opposite to the sign of v and "0" if they are the same.
  • a relaxed requirement from the transmission pattern is that the derivatives will have a constant sign relationship (i.e.- they are not exactly proportional, but their ratio's sign is constant along the pattern).
  • direction-detection is still assured for a single scatterer, but the e ⁇ or probability is higher than in the former case as the number of scatterers gets larger (even without the effect of the singularities).
  • Equation (21) can be looked at as a sum of amplitude-modulated signals of a carrier with frequency nv/ ⁇ .
  • A(x) is now assumed to be asymmetric (e.g.- sawtooth waveform).
  • the detector's signal envelope matches the transmission function for translation in the "positive" direction and is the inverse image the other way.
  • the translation direction is represented by the sign of the first derivative of the detected signal's envelope (and in addition, the magnitude of the envelope derivative is proportional to the magnitude of the translation velocity).
  • An asymmetric transmission pattern enables direction detection for speckle velocimetry.
  • the intensities ⁇ are positive values.
  • dA/dx is constant, then the derivative of the detector signal is indicative of the translation direction.
  • Such a pattern is accomplished using sawtooth transmission pattern.
  • the discontinuities in the pattern add noise to the measurement, requiring the use of an appropriate integration interval in order to limit the e ⁇ or probability.
  • the motion velocity is determined from the frequency of oscillations of the detector signal.
  • a signal proportional to the source amplitude is detected and the resulting signal (termed the "compensation" detector and signal) is subtracted from the detector signal.
  • This detection can be performed, for example, by: • Splitting the source beam with a beamsplitter (which need not be accurately aligned) and directing the diverted beam to the compensation detector, or
  • both the detection of the signals used for translation and direction detection on the one hand and for compensation detection on the other hand are based on first order diffraction by grating 38, but with opposite sign.
  • anti-reflection coatings are used, where appropriate, to reduce unwanted reflections.
  • This device can be used to replace pointing devices other than a mouse.
  • pointing devices used in laptop or palmtop computers.
  • Virtually any one or two dimensional motion can be controlled using such a device.

Abstract

A method for determining the relative motion of a surface with respect to a measurement device, comprising: placing a partially transmitting object as part of the measuring device, adjacent to the surface; illuminating the surface with incident radiation such that the radiation is reflected from portions of the surface towards a detector, wherein at least part of at least one of the incident and reflected radiation passes through the object; detecting the radiation reflected from the surface, such that the detector generates a signal; and determining the relative motion of the surface parallel to the surface, from the detected signal.

Description

OPTICAL TRANSLATION MEASUREMENT
FIELD OF THE INVENTION The present invention is related to the field of velocity and translation measurement and more particularly to methods and apparatus for the non-contact optical measurement of velocity and translation.
BACKGROUND OF THE INVENTION Various optical methods for the measurement of the relative velocity and/or motion of a an object with respect to a measurement system exist. Each method and apparatus is characterized by the kinds of objects and the kinds of motions on which it operates. The kind of measurable objects may be broadly divided into several groups, including:
• A specially patterned object, for example, a scale.
• A reflecting surface, for example, a mirror.
• A small particle (or few particles), for example precursor particles or bubbles suspended in fluid. • An optically contrasting surface, for example, a line or dot pattern.
• An optically diffuse object, for example, blank paper.
The kind of measurable motions may be broadly divided into several groups, including:
• Axial movement toward or away from the measuring device.
• Transverse (or tangential) motion, where the spacing between the measuring device and the object is essentially constant.
• Rotational motion, where the object orientation with respect to the measurement device is changing.
It is also useful to classify the measurement devices according to the number of simultaneously obtainable measurement directions (one, two or three dimensional) and the number of critical components (light sources, light detectors, lenses, etc.).
It should be noted that a specific method may be related to more then one group in the above classification schemes.
A number of systems capable of non-contact measurement of the transverse velocity and/or motion of objects using optical means have been reported. These methods can include Speckle Velocimetry methods and Laser Doppler Velocimetry methods. Other methods of interest for understanding the present invention are Image Velocimetry methods, homodyne/heterodyne Doppler Velocimetry or Interferometry methods and Optical Coherence Tomography (OCT). Speckle Velocimetry methods are generally based on the following operational principles:
• A coherent light source illuminates the object the motion of which needs to be measured.
• The illuminated object (generally an opaque surface) consists of multiple scattering elements, each with its own reflection coefficient and phase shift relative to the other scattering elements.
• The individual reflection coefficients and phase shifts are substantially random. At a particular point in space, the electric field amplitude of the reflection from the object is the vector sum of the reflections from the illuminated scattering elements, with an additional phase component that depends on the distance between the point and each element.
• The light intensity at a point will be high when contributions generally add in phase and low when they generally add out of phase (i.e., subtract).
• On a planar surface (as opposed to a point), an image of random bright and dark areas is formed since the relative phase retardation of the source points depends on the location in the plane. This image is called a "speckle image," composed of bright and dark spots
(distinct "speckles").
• The typical "speckle" size (the typical average or mean distance for a significant change in intensity) depends primarily on the light wavelength, on the distance between the object and the speckle image plane and on the size of the illuminated area. • If the object moves relative to the plane in which the speckle image is observed, the speckle image will move as well, at essentially the same transverse velocity. (The speckle image will also change since some scatterers leave the illuminated area and some enter it).
• The speckle image is passed through a structure comprising a series of alternating clear and opaque or reflecting lines such that the speckle image is modulated. This structure is generally a pure transmission grating, and, ideally is placed close to the detector for maximum contrast.
• The detector translates the intensity of the light that pass through the structure to an electrical signal which is a function of the intensity (commonly a linear function).
• When the object moves with respect to the measuring device, the speckle image is modulated by the structure such that the intensity of light that reach the detector is periodic.
The period is proportional to the line spacing of the structure and inversely proportional to the relative velocity.
• By proper signal analysis, the oscillation frequency can be found, indicating the relative velocity between the object and the measurement device.
For these methods high accuracy frequency determination requires a large detector while high contrast in the signal requires a small detector. A paper by Popov & Veselov, entitled
"Tangential Velocity Measurements of Diffuse Objects by Using Modulated Dynamic Speckle" (SPIE 0-8194-2264-9/96), gives a mathematical analysis of the accuracy of speckle velocimetry.
US patent 3,432,237 to Flower, el. al. describes a speckle velocimetry measuring system in which either a transmission pattern or a pin hole is used to modulate the speckle image. When the pin-hole is used, the signal represents the passage of individual speckles across the pin hole.
US patent 3,737,233 to Blau et. al. utilizes two detectors in an attempt to solve the problem of directional ambiguity which exists in many speckle velocimetric measurements. It describes a system having two detectors each with an associated transmission grating. One of the gratings is stationary with respect to its detector and the other moves with respect to its detector. Based on a comparison of the signals generated by the two detectors, the sign and magnitude of the velocity may be determined.
US Patent 3,856,403 to Maughmer, et al. also attempts to avoid the directional ambiguity by providing a moving grating. It provides a bias for the velocity measurement by moving the grating at a velocity higher then the maximum expected relative velocity between the surface and the velocimeter. The frequency shift reduces the effect of changes in the total light intensity (DC and low-frequency component), thus increasing the measurement dynamic range and accuracy.
PCT publication WO 86/06845 to Gardner, et al. describes a system designed to reduce the amplitude of DC and low frequency signal components of the detector signal by subtracting a reference sample of the light from the source from the speckle detector signal. The reference signal is proportional to the total light intensity on the detector, reducing or eliminating the influence of the total intensity variations on the measurement.
This reference signal is described as being generated by using a beam-splitter between the measured surface and the primary detector by using the grating that is used for the speckle detection also as a beam-splitter (using the transmitted light for the primary detector and the reflected light for the reference detector) or by using a second set of detectors to provide the reference signal. In one embodiment described in the publication the two signals have the same DC component and opposite AC components such that the difference signal not only substantially removes the DC (and near DC) components but also substantially increases the AC component.
In US patent 4,794,384, Jackson describes a system in which a speckle pattern reflected from the measured surface is formed on a 2D CCD array. The surface translation in 2 dimensions is found using electronic correlation between successive images. He also describes an application of his device for use as a "padless optical mouse."
Image velocimetry methods measure the velocity of an image across the image plane. The image must include contrasting elements. A line pattern (much like a grating) space- modulate the image, and a light-sensitive detector is measuring the intensity of light that pass through the pattern. Thus, a velocity-to-frequency relation is formed between the image velocity and the detector AC component. Usually, the line pattern moves with respect to the detector so that the frequency is biased. Thus, the direction ambiguity is solved and the dynamic range expanded.
A paper by Li and Aruga, entitled "Velocity Sensing by Illumination with a Laser-Beam Pattern" (Applied Optics, 32, p.2320, 1993) describes image velocimetry where the object itself is illuminated by a periodic line structure (instead of passing its image through such a pattern). The line pattern is obtained by passing an expanded laser beam through periodic transmission grating (or line structure). According to the suggested method the object still needs to have contrasting features. There exist a number of differences between Image Velocimetry (IV) and Speckle
Velocimetry (SV). In particular, in SV the random image is forced by the coherent light source, whereas in IV an image with proper contrasting elements is already assumed. Furthermore, in SV the tangential velocity of the object is measured, whereas in IV the angular velocity is measured (the image velocity in the image plane is proportional to the angular velocity of the line of sight).
In US Patent 3,511,150 to Whitney et. al., two-dimensional translating of line patterns creates a frequency shift. A single rotating circular line pattern creates all the necessary translating line patterns at specific elongated apertures in a circular mask. The frequency shift is measured on-line using an additional detector measuring a fixed image. The line pattern is divided to two regions, each one adapted for the measurement of different velocity range. The system is basically intended for image motion compensation in order to reduce the image blur in aerial photography. Also, it is useful for missile homing heads.
US patent 2,772,479 to Doyle describes an image velocimetry system with a frequency offset derived from a grating on a rotating belt.
Laser Doppler Velocimeters generally utilize two laser beams formed by splitting a single source which interfere at a known position. A light-scattering object that passes through the interfering space scatters light from both beams to a detector. The detector signal includes an oscillating element with frequency that depends on the object velocity. The phenomena can be explained in two ways. One explanation is based on an interference pattern that is formed between the two beams. Thus, in that space the intensity changes periodically between bright and dark planes. An object passing through the planes scatters the light in proportion to the light intensity. Therefore, the detected light is modulated with frequency proportional to the object velocity component perpendicular to the interference planes. A second explanation considers that an object passing through the space in which both light beams exist, scatters light from both. Each reflection is shifted in frequency due to the Doppler effect. However, the Doppler shift of the two beams is different because of the different angles of the incident beams. The two reflections interfere on the detector, such that a beat signal is established, with frequency equal to the difference in the Doppler shift. This difference is thus proportional to the object velocity component perpendicular to the interference planes.
It is common to add a frequency offset to one of the beams so that zero object velocity will result in a non-zero frequency measurement. This solves the motion direction ambiguity (caused by the inability to differentiate between positive and negative frequencies) and it greatly increases the dynamic range (sensitivity to low velocities) by producing signals far from the DC components. The frequency offset also has other advantages related to signal identification and lock-on.
US Patent 5,587,785 to Kato, et. al. describes such a system. The frequency offset is implemented by providing a fast linear frequency sweep to the source beam before it is split. The method of splitting is such that a delay exists between the resulting beams. Since the frequency is swept, the delay results in a fixed frequency difference between the beams.
Multiple beams with different frequency offsets can be extracted by further splitting the source with additional delays. Each of these delays is then used for measuring a different velocity dynamic range. A paper by Matsubara, et al., entitled "Simultaneous Measurement of the Velocity and the Displacement of the Moving Rough Surface by a Laser Doppler Velocimeter" (Applied Optics, 36, p. 4516, 1997) presents a mathematical analysis and simulation results of the measurement of the transverse velocity of a rough surface using an LDV. It is suggested that the displacement along the axial axis can be calculated from measurements performed simultaneously by two detectors at different distances from the surface.
In Homodyne/Heterodyne Doppler Measurements, a coherent light source is split into two beams. One beam (a "primary" beam) illuminates an object whose velocity is to be measured. The other beam (a "reference" beam) is reflected from a reference element, usually a mirror, which is part of the measurement system. The light reflected from the object and from the reference element are recombined (usually by the same beam splitter) and directed to a light-sensitive detector.
The frequency of the light reflected from the object is shifted due to the Doppler effect, in proportion to the object velocity component along the bisector between the primary beam and the reflected beam. Thus, if the reflected beam coincides with the primary beam, axial motion is detected.
The detector is sensitive to the light intensity, i.e.- to the square of the electric field. If the electric field received from the reference path on the detector is Eg(t) = Eocos(cø()t + φo) and the electric field received from the object on the detector is Eι (t) = E^ cos(ωιt + φj) , then
the detector output signal is proportional to (EQ + Eι ) = EQ + EQEJ + E\ .
The first term on the right side of the equation is averaged by the detector time-constant and results in a DC component. The intensity of the reference beam is generally much stronger than that of the light reaching the detector from the object, so the last term can usually be neglected. Developing the middle term:
BQE\ = EQEI cos(ω()t + φo)cos(ωιt + φι )
= l/2E0Eι[cos((ωo +ωι)t + φ0 + φi) + cos((ω0 -ω1)t + φo -φi)]
From this equation it is evident that EQEI includes two oscillating terms. One of these terms oscillates at about twice the optical frequency, and is averaged to zero by the detector time-constant. The second term oscillates with frequency ωø - ωi , i.e.- with the same frequency as the frequency shift due to the Doppler effect. Thus, the detector output signal contains an oscillating component with frequency indicative of the measured velocity.
It is common to add a frequency offset to the reference beam. When such a frequency bias is added, it is termed Heterodyne Detection.
US patent 5,588,437 to Byrne, et al. describes a system in which a laser light source illuminates a biological tissue. Light reflected from the skin surface serves as a reference beam for homodyne detection of light that is reflected from blood flowing beneath the skin. Thus, the skin acts as a diffused beam splitter close to the measured object. An advantage of using the skin as a beam splitter is that the overall movement of the body does not effect the measurement. Only the relative velocity between the blood and the skin is measured.
The arrangement uses two pairs of detectors. Each pair of detectors is coupled to produce a difference signal. This serves to reduce the DC and low-frequency components interfering with the measurement. A beam scanning system enables mapping of the two- dimensional blood flow.
In Optical Coherence Tomography (OCT), a low-coherence light source ("white light") is directed and focused to a volume to be sampled. A portion of the light from the source is diverted to a reference path using a beam-splitter. The reference path optical length is controllable. Light reflected from the source and light from the reference path are recombined using a beam-splitter (conveniently the same one as used to split the source light). A light- sensitive detector measures the intensity of the recombined light. The source coherence length is very short, so only the light reflected from a small volume centered at the same optical distance from the source as that of the reference light coherently interferes with the reference light. Other reflections from the sample volume are not coherent with the reference light. The reference path length is changed in a linear manner (generally periodically, as in sawtooth waveform). This allows for a sampling of the material with depth. In addition a Doppler frequency shift is introduced to the measurement, allowing for a clear detection of the coherently-interfering volume return with a high dynamic range.
In conventional OCT, a depth profile of the reflection magnitude is acquired, giving a contrast image of the sampled volume. In more advanced OCT, frequency shifts, from the nominal Doppler frequency, are detected and are related to the magnitude and direction of relative velocity between the sampled volume (at the coherence range) and the measurement system.
US patent 5,459,570 to Swanson, et al. describes a basic OCT system and numerous applications of the system.
A paper by Izatt et al., entitled "In Vivo Bidirectional Color Doppler Flow Imaging of Picoliter Blood Volumes Using Optical Coherence Tomography" (Optics Letters 22, p.1439, 1997) describes an optical-fiber-based OCT with a velocity mapping capability. An optical- fiber beam-splitter is used to separate the light paths before the reflection from the sample in the primary path and from the mirror in the reference path and combine the reflections in the opposite direction. A paper by Suhara et al., entitled "Monolithic Integrated-Optic Position/Displacement Sensor Using Waveguide Gratings and QW-DFB Laser" (IEEE Photon. Technol. Lett. 7, p.1195, 1995) describes a monolithic, fully integrated interferometer, capable of measuring variations in the distance of a reflecting mirror from the measuring device. The device uses a reflecting diffraction element (focusing distributed Bragg reflector) in the light path from the source as a combined beam-splitter and local oscillator reflector. Direction detection is achieved by an arrangement that introduces a static phase shift between signals of the detectors.
Each of the above referenced patents, patent publications and references is incorporated herein by reference. SUMMARY OF THE INVENTION
The present invention in its broadest form provides an Optical Translation Measurement (OTM) method and device, capable of providing information indicative of the amount and optionally the direction of relative translation between the device and an adjacent object. Preferably, the object is at least partly rough and is closely spaced from the device. As used herein, the terms "rough" or "diffuse" mean optically irregular or non-uniform. In particular, the object may have a diffuse opaque or semi-transparent surface such as a paper. This specification deals mainly with determining the translation or velocity of such diffuse surfaces. However, it should be understood that many of the methods of the invention may also be applicable to determination of translation of other types of objects such as small scattering particles, possibly suspended in fluid. Translation of the object means that its rotation in space may be neglected. In a first aspect thereof, the invention provides heterodyne or homodyne detection of non-Doppler, non-speckle-image signals derived from changes in the phase and/or the amplitude of reflection from an optically irregular surface.
In a second aspect thereof, applicable to various methods of motion or velocity detection, in addition to the preferred embodiments thereof, the invention provides a system in which a reflector which reflects part of the incident light is placed next to the surface whose motion is to be measured. The reflector provides a local oscillator signal which is inherently coherent with the light which is reflected from the surface. This aspect of the invention is applicable to both Doppler and non-Doppler methods of motion detection. In a preferred embodiment of the invention, the partial reflector is an apertured reflector in which the illumination of the surface whose motion is measured pass through the aperture. In a preferred embodiment of the invention, the partial reflector covers a portion of the measured surface and has a substantial amount of transmission. In this preferred embodiment of the invention, the reflections from the surface pass through the partial reflector. A combination of apertureing and partial transmission is often useful, especially in preferred embodiments of the invention which utilize the third aspect of the invention.
In a third aspect of the invention, a non-symmetrical transmission pattern is provided to aid in determining the direction of motion of the surface.
In a fourth aspect of the invention, a phase shift is introduced between the reflection from the partial reflector and the reflection from the surface. This phase shift enables the determination of the direction of motion, increases the dynamic range and improves the signal- to-noise ratio. This phase shift may, in some preferred embodiments of the invention, be dynamic, i.e., time varying. Such phase variations are conveniently performed by moving the reflector either perpendicularly to the surface or parallel to the surface or a combination of both. Also, the movement may be of a pattern on the reflector, e.g.- the movement of a standing wave acting as a grating in a Surface Acoustic Wave (SAW) component. In this respect it is the pattern on the reflector that moves, and not the whole reflector. Alternatively, the phase shift is introduced by periodically varying the optical path length between the reflector and the surface, e.g. by inserting a piezo-electric material in the optical path.
The phase shift may also be a static phase shift. Conveniently, this static phase shift is accompanied by a change in polarization of one of the beams (or a part of the energy in the beam). The direction of motion is determined by a measurement of the phase change and more particularly by measurement of the sign of the phase change. In a preferred embodiment of the invention, the phase of a portion of a beam whose phase is not changed is compared with the phase of a portion which is changed, to determine the direction of motion.
A fifth aspect of the invention provides for Doppler based detection of motion of a surface in a direction parallel to the surface. In this aspect of the invention, a single beam may be incident at an angle to the surface or even perpendicular to the surface.
A sixth aspect of the invention provides for simultaneous two or three dimensional translation detection using a single illuminating beam and a single reflector to provide local oscillator reference beams. In a preferred embodiment of the invention, the signal generated by a single detector is used to determine the translation in two dimensions.
In a seventh aspect of the invention, a surface is illuminated with a preferably periodically spatially varying illumination and a spatial filter is provided such that the illumination is reflected from the surface such that substantially only a single spatial frequency of the reflected radiation is incident on the detector.
In some preferred embodiments of the invention which incorporate this aspect of the invention, the spatial filter comprises a lens having a focal point and a pinhole which is placed at the focal point of the lens. Preferably, the illumination of the surface is collimated and the spatial filter filters the reflected illumination such that only radiation reflected from the surface substantially in a single direction is incident on the detector.
A device, according to a preferred embodiment of the invention, includes a light source, a grating, a spatial filter, a photo-detector, and signal processing electronics. The light source provides at least partially coherent radiation, which is directed toward the surface. An optical grating is placed between the surface and the light source, preferably close to the surface. The light reflected from the surface interferes with the light that is reflected from the grating itself. The detector signal includes an oscillating component, that is representative of the surface translation relative to the optical device. The interference may take place with the normal reflection from the grating or with light diffracted at any of the grating orders. Most preferably, the light passes through a spatial filter prior to detection by the detector. Two dimensional translation measurement may be achieved by using orthogonal reflection orders from a two- dimensional grating or by utilizing two separate gratings for the two directions. A third dimension may be deduced by vector calculation of the translations measured in two different orders at the same axis (e.g.- 0 and 1, 1 and 2, -1 and 1, etc.), or without an additional detector, simultaneously using different signal analysis techniques on the same signal.
Optional detection of the direction of translation (as opposed to it's absolute magnitude) is preferably achieved by modulating the grating position to provide a frequency offset. Alternatively, a varying optical path length between the grating and the surface introduces the frequency offset. Alternatively, an asymmetric pattern for the grating transmission and appropriate signal manipulation/processing may be used. Alternatively, the direction may be determined by other means.
The method and device of the invention are applicable to a wide range of applications that require measurement of translation. One such application is a "padless optical mouse", that can effectively control a cursor movement by moving the mouse across an optically diffuse surface such as a paper or a desk-top. Another exemplary application for the invention is for a "touch-point", that translates finger movement over a device aperture to control a cursor or any other translation or velocity controlled entity. In accordance with a preferred embodiment of the invention, the measurement apparatus comprises a light source for providing at least partially coherent radiation. The source radiation is directed toward an optical one-dimensional or two-dimensional grating, which is preferably close to the reference surface. The light reflections from the grating and from the surface interfere, and the light is collected through a spatial filter (for example, a lens and a pin-hole at its focal point) into a light-detector. The resulting interference signal contains beats related to the relative translation of the optical apparatus and the surface. Direct measurement of the amount of translation is performed by counting the "zero crossings" of the oscillating detector signal. In preferred embodiments of the invention, the translation is measured directly by counting zero crossings and is thus not subject to errors caused by velocity changes. For preferred embodiments of the invention, substantially instantaneous position determination is established.
In many applications the translation direction as well as its magnitude is required. In a preferred embodiment of the invention this is accomplished by incorporating a phase shifting device (such as a piezoelectric transducer) which creates an asymmetric phase shift pattern (typically a saw-tooth waveform) between the light reflected from the grating and from the surface, enabling simple extraction of the direction information. Alternatively, direction detection is accomplished by using a preferably specially-designed asymmetric transmission pattern for the grating/matrix (such as a saw-tooth transmission or other form as described herein) with appropriate signal processing/manipulation on the detector output signal. An asymmetric transmission pattern provides means for motion direction detection in other velocimetry methods as well, such as speckle velocimetry.
A speckle-free, coherent detection of translation may be determined by collecting the scattered light (the light which passes through the grating and is reflected from the moving surface) with a spatial filter, such as a combination of a focusing lens and a pinhole aperture (or single mode optical fiber) at the focal position of the lens. The light reflected from the surface is combined with a local oscillator light field (which is preferably the light reflected or diffracted by the grating itself), which field is preferably a part of the light beam that also passes through the spatial filter. The interference with the strong local oscillator light source provides amplification of the detected signal by an intensity-sensitive photodetector. This coherent detection method is termed homodyne detection.
The spatial filter is operative to spatially integrate light reflected from the surface to a detector, such that the relative phases of the reflections from different locations on the surface are essentially unchanged when the surface moves with respect to the detector. Furthermore, the phase of a scatterer on the surface (as measured at the detector) depends linearly on the surface translation. Also, the spatial filter is ideally used to filter the local oscillator such that the detector will integrate over no more than a single interference fringe resulting from the interference between the local oscillator and the light reflected from the surface.
In one extreme case, the light incident on the surface is perfectly collimated (i.e.- it is a plane wave). Thus, the spatial filter may simply be a lens with a pinhole positioned at it's focal point. Any translation of the surface does not change the relative phases of the light integrated by the spatial filter. The local oscillator formed by the reflection or the diffraction from the reflector or grating is also perfectly collimated, so that it can also be passed through the spatial filter (the spatial filter is positioned such that the image of the source falls on or within the pinhole). This forces a single interference fringe on the detector. No limitations are imposed (with regard to spatial filtering) on the spacing between the reflector and the surface.
In another extreme case, the spacing between the surface and the reflector is negligible. This allows for the use of a substantially non-collimated incident beam while still maintaining the relative phases of the reflections from the surface irrespective of it's translation and also maintaining the same focusing point for the local oscillator and the reflection from the surface. Optionally, the spatial filter may be implemented with a lens and a pinhole positioned at the image plane of the reflection of the source as a local oscillator. In order to have (at most) a single speckle integrated by the detector, the pinhole size should not exceed the size of about a single speckle formed by the reflection from the surface
(for this reason, the measurement may be termed "speckle-free"). Thus, if the detector itself is small enough, it may serve as an integral part of the spatial filter and a pin-hole is not required.
The requirements of unchanged relative phases and single interference fringe with the local oscillator at the detector can be fulfilled in a multitude of optically equivalent ways. In particular, the requirement may be established using a single converging lens positioned before or after the reflection of the light from the reflector. Alternatively, the lens and the reflector can be combined in a single optical device. Also, a collimating lens may be positioned between the beamsplitter and the surface (i.e.- only light to and from the surface pass through this lens). Non-ideal spatial filtering (as when the pin hole is too large, or when it is out of focus for either the reflection from the surface or the local oscillator or both), results in deterioration of the signal and possibly the addition of noise to the measurement. The level of deterioration depends on the amount and kind of deviation from the ideal. In a preferred method according to the present invention, both the surface illumination and the reference light are provided using a single optical element, preferably a grating. The surface and reference light share a single optical path through all of the optical elements in the device. Moreover, the spatial amplitude and/or phase modulation, imposed on the light reaching the surface by the grating, provide additional means for measuring the surface's translation. In particular, tangential translation can be measured even for specular reflection from the grating, where no Doppler shift exists, and identification of the direction of motion can also be achieved.
There is thus provided, in accordance with a preferred embodiment of the invention, a method for determining the relative motion of a surface with respect to a measurement device, comprising: placing a partially transmitting object, as part of the measuring device, adjacent to the surface; illuminating the surface with incident radiation such that the radiation is reflected from portions of the surface towards a detector, wherein at least part of at least one of the incident and reflected radiation passes through the object; detecting the radiation reflected from the surface, such that the detector generates a signal; and determining the relative motion of the surface parallel to the surface, from the detected signal.
Preferably, the transmission of the object is spatially varying.
In a preferred embodiment of the invention, the object is partially reflecting, part of the incident radiation is reflected or diffracted by the object towards a detector, as a reference radiation and detection of the radiation is coherent, utilizing said reference radiation. There is further provided, in accordance with a preferred embodiment of the invention a method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface with incident radiation such that the radiation is reflected from portions of the surface towards a detector; placing a partially reflecting object, which is part of the measuring device, adjacent to the surface, wherein part of the incident radiation is reflected or diffracted by the object towards the detector, as a reference radiation; coherently detecting the radiation reflected from the surface utilizing the reference radiation, such that the detector generates a signal; and determining the relative motion of the surface parallel to the surface, from the detected signal.
Preferably, the reflection of the object is spatially varying. Preferably, spatially varying comprises periodic spatial variation.
In a preferred embodiment of the invention, the object is a partially transmitting object and wherein at least part of at least one of the incident and reflected radiation passes through the object.
In a preferred embodiment of the invention, placing an object adjacent to the surface comprises placing a grating adjacent to the surface.
In a preferred embodiment of the invention, placing a grating adjacent to the surface comprises placing the grating sufficiently close to the surface such that the surface is in the near field of the grating.
In a preferred embodiment of the invention placing a grating adjacent to the surface comprises placing the grating sufficiently far from the surface such that the surface is outside the near field of the grating.
Preferably, the detected radiation is at least partly coherent.
In a preferred embodiment of the invention the object and the surface are situated within a distance which is less than the coherence length of the radiation which reaches the detector. In a preferred embodiment of the invention, the radiation reflected from the surface is frequency shifted from that of the radiation reflected from or diffracted by the object and determining the motion comprises determining the motion based on the frequency shift.
Preferably determining the motion comprises determining variations in the amplitude of the signal with position. Preferably, the motion is determined from zero crossings of the detected signal.
In a preferred embodiment of the invention, the object has a transmission characteristic that is spatially non-symmetric. Preferably, the method includes determining the direction of the relative motion based on a characteristic of the signal caused by said non-symmetry.
There is further provided, in accordance with a preferred embodiment of the invention a method for determining the relative motion of a surface with respect to a measurement device comprising: placing a partially transmitting object, which is part of the measuring device, adjacent to the surface; illuminating the surface with incident radiation such that the radiation is reflected from portions of the surface towards a detector, wherein at least part of at least one of the incident and reflected radiation passes through the object; detecting the radiation reflected from the surface, such that the detector generates a signal; and determining the relative motion of the surface parallel to the surface, from the detected signal.
Preferably, the method comprises: varying the phase between the radiation reflected from or diffracted by the object and at least a portion of the radiation reflected from the surface.
There is further provided, in accordance with a preferred embodiment of the invention, a method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface with incident radiation such that radiation is reflected from portions of the surface and such that radiation is reflected from or diffracted by the object toward a detector; placing a partially reflecting object, which is part of the measuring device, adjacent to the surface, wherein part of the incident radiation is reflected or diffracted by the object towards the detector, as a reference radiation; coherently detecting the radiation reflected from the surface utilizing the radiation reflected from or diffracted by the object as a local oscillator to form a signal; determining the relative motion of the surface from the signal; varying the phase of the radiation reflected from or diffracted by the object with respect to that reflected from the surface; and determining the direction of relative motion parallel to the surface based on a characteristic of the signal caused by said varying relative phase.
Preferably, placing a reflector adjacent to the surface comprises placing a grating adjacent to the surface.
In a preferred embodiment of the invention varying the phase comprises periodically varying the phase. Preferably, determining the direction of relative motion comprises determining the direction of relative motion based on a characteristic of the signal caused by said varying relative phase.
In a preferred embodiment of the invention varying the phase comprises causing the object to move periodically substantially in the direction of the motion being measured. Alternatively or additionally varying the phase comprises causing the object to move periodically substantially perpendicularly to the direction of the motion being measured.
In a preferred embodiment of the invention, varying the phase comprises providing a transparent material between the object and the surface and electrifying the material such that its optical length in the direction of the radiation varies. Preferably, the transparent material is a piezoelectric material.
In a preferred embodiment of the invention the method includes determining both the magnitude and direction of the translation utilizing a single detector. In a preferred embodiment of the invention, varying the phase comprises, introducing a static phase change and determining the direction of relative motion comprises determining the direction of relative motion based on a characteristic of the signal caused by said phase change.
A method according to a preferred embodiment of the invention includes dividing the radiation that is reflected from the surface into a first radiation having a first phase and a second radiation having a second phase. Preferably, the first and second radiations have different polarizations. Preferably, dividing comprises passing the radiation incident on the surface through a birefringent material. Preferably, the method includes passing the radiation reflected from the surface through the birefringent material. Preferably, the method includes placing the birefringent material between the object and the surface. Preferably, the method includes determining the direction of translation from the sign of the phase difference between the first and second radiations.
In a preferred embodiment of the invention the method includes determining the magnitude and direction of the translation utilizing two detectors which produce different signals. There is further provided, in accordance with a preferred embodiment of the invention, a method for determining the relative motion of a surface with respect to a measurement device comprising: placing an apertured reflector, which is part of the measurement device, adjacent to the surface; illuminating the surface with incident radiation such that radiation is reflected from portions of the surface and such that radiation is reflected from or diffracted by the apertured reflector toward the detector; coherently detecting the radiation reflected from the surface utilizing the radiation reflected from or diffracted by the apertured reflector as a local oscillator to form a signal; determining the relative motion of the surface perpendicular to and parallel to the apertured reflector from the signal.
Preferably, coherently detecting comprises: detecting amplitude or phase variations of the reflected radiation; and detecting a frequency shift of the reflected radiation; and determining the relative motion comprises: measuring relative motion of the surface in a direction parallel to the apertured reflector responsive to at least one of the detected amplitude or phase variations; and measuring relative motion of the surface in a direction perpendicular to the surface of the apertured reflector responsive to the detected frequency shift.
Preferably the method comprises periodically moving the apertured reflector surface in a direction perpendicular to its surface to add a periodic phase shift to the radiation reflected therefrom and utilizing said phase shift to measure the motion of the surface. There is further provided, in accordance with a preferred embodiment of the invention a method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface, from a source, with incident radiation such that radiation is reflected from portions of the surface toward the detector; spatially filtering the reflected radiation such that the phase of the optical radiation exiting the spatial filter from a given scatterer on the surface is substantially constant or linearly related to the translation of the surface; generating a signal by the detector responsive to the radiation incident on the detector; and determining the relative motion of the surface from the signal.
Preferably illuminating comprises illuminating the surface with spatially varying radiation. Preferably, illuminating the surface comprises illuminating the surface through an apertured reflector placed adjacent to the surface which reflects or diffracts radiation to the detector. Preferably, generating a signal comprises coherent detection of the radiation reflected from the surface utilizing the radiation reflected or diffracted from the apertured reflector.
In a preferred embodiment of the invention determining the relative motion comprises utilizing a Doppler shift of the reflected radiation.
In a preferred embodiment of the invention illumination of the surface is substantially collimated and the spatial filter filters the reflected illumination such that substantially only a single spatial frequency of the reflected radiation is incident on the detector.
In a prefeπed embodiment of the invention, illumination of the surface is substantially collimated and spatial filtering filters the reflected illumination such that only radiation reflected from the surface substantially in a single direction is incident on the detector.
In a preferred embodiment of the invention, spatial filtering comprises focusing the reflected radiation with a lens having a focal point and placing a pinhole at the focal point of the lens.
In a preferred embodiment of the invention, spatial filtering comprises focusing the reflected radiation with a lens having a focal point and placing a single mode optical fiber at the focal point of the lens to transfer radiation to the detector.
In a prefeπed embodiment of the invention spatial filtering comprises focusing the reflected radiation with a lens and placing a pinhole at an image of the source.
In a prefeπed embodiment of the invention, spatial filtering comprises focusing the reflected radiation with a lens and placing a single mode optical fiber at an image of the source to transfer radiation to the detector.
There is further provided in accordance with a prefeπed embodiment of the invention a method for determining the relative motion of a surface with respect to a measurement device comprising: placing an object, having at least a quasi-continuous transmission function, adjacent to the surface; illuminating the surface with incident radiation such that radiation is reflected from portions of the surface toward a detector; detecting the radiation reflected from the surface utilizing the detector to generate a signal; and determining the relative motion of the surface from the signal.
Preferably, the object has an asymmetric transmission function and determining the relative motion comprises determining the direction of motion based on the detected signal.
Preferably, radiation is reflected from or diffracted by the object toward the detector and detection is coherent detection utilizing the radiation reflected from or diffracted by the apertured reflector as a local oscillator to form a signal.
There is further provided, in accordance with a prefeπed embodiment of the invention, a method for determining the relative motion of a surface with respect to a measuring device comprising: illuminating the surface with incident visible or infrared radiation such that radiation is reflected from the surface to illuminate a detector with radiation which is not an image of a point on or a portion of the surface; simultaneously illuminating the detector with reference radiation derived from said incident radiation; coherently detecting the reflected illumination of the detector utilizing said reference radiation such that the detector generates a signal; determining the relative motion of the surface parallel to the surface, based on variations of the signal with time.
In a prefeπed embodiment of the invention, the incident radiation is at a given wavelength and the reference radiation is at the same wavelength such that the coherent detection is homodyne detection.
Preferably, the method includes spatially varying the illumination of the surface. Preferably spatially varying the illumination of the surface comprises illuminating the surface through an apertured reflector.
In a preferred embodiment of the invention spatially varying the illumination of the surface comprises illuminating the surface through a transmission grating having spatially varying periodic transmission. In a preferred embodiment of the invention spatially varying the illumination of the surface comprises: illuminating the surface through a grating which specularly reflects a portion of the radiation incident upon it toward the detector to form said reference radiation.
There is further provided, in accordance with a preferred embodiment of the invention a method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface with visible or infrared radiation such that radiation is reflected from portions of the surface toward a detector; coherently detecting the radiation reflected from the surface; and determining the relative motion of the surface, in a direction parallel to the surface, from a characteristic of the signal based on a Doppler shift of the reflection reflected from the surface.
Preferably, the method includes placing an apertured reflector adjacent to the surface, wherein said coherent detection utilizes radiation reflected from or diffracted toward the detector from the apertured reflector as a local oscillator. Preferably the apertured reflector is a grating and radiation diffracted by the grating is used in determining the motion.
In prefeπed embodiments of the invention, the illumination is perpendicularly incident on the surface.
In prefeπed embodiments of the invention, the surface is an optically diffusely reflecting surface.
Preferably, the surface has no markings indicating position.
There is further provided, in accordance with a preferred embodiment of the invention apparatus for determining the relative motion of a surface, comprising: a partially transmitting object situated adjacent to the surface; a source of radiation which illuminates the surface with incident radiation such that radiation is reflected from portions of the surface towards a detector, wherein at least part of at least one of the incident and reflected radiation passes through the object; a detector which detects the reflected illumination such that the detector generates a signal; and circuitry which determines relative motion of the surface parallel to the surface with respect to the apparatus from the detected signal.
There is further provided, in accordance with a preferred embodiment of the invention an optical mouse comprising: a housing having an aperture facing a surface; and an optical motion detector which views the surface through the aperture, wherein the optical motion detector utilizes the method of the invention to determine the translation of the housing with respect to the surface. There is further provided, in accordance with a prefeπed embodiment of the invention, a touch point for use as a control device comprising: a housing having an aperture; and an optical detector which determines the motion of a finger which is translated across the aperture. In a preferred embodiment of the invention the touch point utilizes the method of the invention to determine the translation.
There is further provided, in accordance with a prefeπed embodiment of the invention, a pointer device comprising: a first touch point according to the invention and circuitry which moves a pointer responsive thereto; and a second touch point according to the invention and circuitry which causes scrolling responsive thereto. There is further provided, in accordance with a prefeπed embodiment of the invention, a combination mouse/touch point for use as a pointer for a computer comprising: a housing having an aperture; an optical detector which determines the motion of an object which is translated across the aperture; and means for determining whether the aperture is upward or downward facing.
Preferably the optical detector utilizes the method of the invention to determine the translation.
There is further provided, in accordance with a prefeπed embodiment of the invention, a scanner for reading a document by movement of the scanner over the document comprising: an optical reading head which detects patterns on the surface of the document; and an optical detector which determines the motion of the scanner as it is translated across the surface of the document, wherein the optical detector utilizes the method of the invention to determine the translation.
In a preferred embodiment of the invention the patterns are printed patterns. Alternatively, the patterns are handwritten patterns. Preferably the patterns are a signature.
There is further provided, in accordance with a prefeπed embodiment of the invention, an encoder comprising: an optically diffusely reflecting surface; and an optical detector having relative motion with respect to the surface, wherein the optical detector measures relative motion with respect to the surface without utilizing markings on the surface.
There is further provided, in accordance with a preferred embodiment of the invention an encoder comprising: an optically diffusely reflecting surface having no markings other than reference markings; and an optical detector having relative motion with respect to the surface, wherein the optical detector measures relative motion with respect to the surface relative to the reference markings. In a prefeπed embodiment of the invention the surface is the surface of a disk which rotates about an axis and wherein the detector measures the rotation of the disk. Preferably, the encoder utilizes the method of the invention.
There is further provided, in accordance with a preferred embodiment of the invention a virtual pen comprising an encoder according to the invention and circuitry which translates said measured relative motion into written or graphical data. Preferably, the virtual pen utilizes the method of the invention.
There is further provided, in accordance with a preferred embodiment of the invention a device for moving a sheet of paper comprising means for moving the paper and an optical detector which measures the movement of the paper without utilizing any markings on the paper. Preferably the optical detector utilizes the method of the invention
There is further provided, in accordance with a prefeπed embodiment of the invention a document scanner comprising a device for moving a sheet of paper according to the invention, a reading head which reads information from the paper and a memory which stores the information in memory locations responsive to the measurement of movement of the paper.
There is further provided, in accordance with a prefeπed embodiment of the invention a printing machine comprising a device for moving a sheet of paper according to the invention, a memory which contains information to be printed on the sheet of paper and a printing head which prints the information responsive to the measurement of movement of the paper. There is further provided a facsimile machine comprising a scanner according to the invention, a printer according to the invention or both.
There is further provided, in accordance with a preferred embodiment of the invention, a method for determining the direction of relative motion of a surface with respect to a measurement device comprising: illuminating the surface with incident radiation such that radiation is reflected from portions of the surface toward a detector; placing an object, having an asymetric transmission function, adjacent to the detector; detecting the radiation reflected from the surface utilizing the detector to generate a signal; and determining the direction of relative motion of the surface from the signal.
BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more clearly understood from the following description of the prefeπed embodiments of the invention read in conjunction with the attached drawings in which:
Fig. 1 is a schematic representation of a prefeπed embodiment of a motion transducer, in accordance with a prefeπed embodiment of the invention;
Fig. 2 is a graph of a grating transmission function, in accordance with a prefeπed embodiment of the invention;
Figs. 3A, 3B and 3C are schematic representations of prefeπed embodiments of integrated motion transducers, in accordance with prefeπed embodiments of the invention;
Fig. 4 is a schematic diagram of an optical mouse in accordance with a prefeπed embodiment of the invention; Figs. 5 A and 5B are schematic diagrams of a mouse/finger translation measurement device, in accordance with a prefeπed embodiment of the invention;
Fig. 6 is a schematic diagram of a scanning pen in accordance with a prefeπed embodiment of the invention;
Fig. 7 is a diagram of a rotary encoder, in accordance with a prefeπed embodiment of the invention;
Fig. 8 is a schematic diagram of a fiber-optic-based translation measurement device, in accordance with a preferred embodiment of the invention; and
Fig. 9 is a simplified and generalized block diagram of electronic circuitry, suitable for use in prefeπed embodiments of the invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
Fig. 1 shows apparatus 10 for the measurement of the translation of a surface 12, in accordance with a preferred embodiment of the invention. Apparatus 10 comprises a source of at least partially coherent, preferably collimated optical radiation 14, such as a laser. Preferably, the laser is a diode laser, for example a low power infra-red laser. While other wavelengths can be used, an infra-red laser is preferred since it results in eye-safe operation. The source is preferably collimated. However, a non-collimated source may be used if compensation as described below is used. While it is desirable to use a collimated source from power considerations, the collimation need not be particularly good.
Apparatus 10 also includes a one-dimensional or two dimensional reflective grating 16 which is closely spaced from surface 12. The limitations as to spacing of grating 16 from surface 12 are described below. Light which is reflected from (or diffracted by) grating 16 and light reflected by surface 12 are both incident on a spatial filter (composed of a lens 18 and a pinhole 20) before being detected by an optical detector 22. The resulting interference gives rise to a beat signal that depends on the motion of the surface. It should be noted that this and other Figs, show an exaggerated spacing between grating 16 and surface 12, for clarity. As indicated from Fig. 1, radiation is reflected from the surface in substantially all directions. This radiation is shown only in Fig. 1 and not in the other drawings for clarity of presentation. In Fig. 1 the light is seen as being incident on the surface from an angle; however, it is possible for the light to be incident at the normal to grating 16. Moreover, while Fig. 1 shows the incident light angle equal to the detection angle, such that light reflected from the grating (or zeroth order diffraction) is used for the local oscillator, first or higher order diffraction by the grating can be effectively used. Zero order has the advantages that it is wavelength independent (stability of the wavelength is not important). The incident light can be pulsed or continuous. In Fig. 1, light diffracted at the -1 and +1 orders are indicated by reference numbers 19 and 21 respectively. Light which is scattered by the surface is indicated by reference number 17.
In the prefeπed embodiment of the invention shown in Fig. 1 , speckle- free, coherent detection (homodyne or heterodyne, homodyne shown in Fig. 1) is used to determine tangential motion. Such detection results in an intrinsic amplification of the signal used for measurement resulting in a high dynamic range.
The reference local oscillator field for the coherent detection is provided by reflections from grating 16, placed close to the moving surface. The interference of the reflections from the grating and the moving surface on the detector give rise to a translation dependent oscillating signal. The incorporation of a near-surface reflection from a grating as the origin of the local oscillator field may give multiple advantages, including at least some of the following: 1. The grating is a single element that combines the roles of a beam splitter and a mirror in a coherent homodyne/heterodyne detection optical setup, thus making the optical system simple, robust and with few alignment requirements. 2. The grating causes spatially periodic intensity and/or phase modulation of the illumination reflected from the surface, if the surface is placed within the near field of the grating. This enables detection of translation using the specular (zeroth order) reflection as the reference wave.
3. High order reflections (±lst, ±2nc% etc.) serve as local oscillator fields for higher resolution detection of the surface's translation. A translation dependent phase shift between the reference and surface waves at non-specular reflection orders produce oscillations representative of the translation.
4. Translation detection can be frequency biased by periodic shifting of the grating position (e.g. sawtooth modulation), enabling determination of direction as well as magnitude of the translation.
5. A two-dimensional grating provides reference (local oscillator) waves and modulation of the illumination of the surface and reflections from it for two orthogonal translation directions in a single element, for a full two-dimensional transverse motion measurement coverage.
6. Measurement at different grating orders provides different components of the translation or velocity vector of the surface. For specular reflection, for example, translation along the axis perpendicular to the grating can be measured independently of translation in the other directions. This allows for three dimensional translation measurement by adding the measurement or the calculation of the axial component for two measurements performed for the same transverse axis but in different grating orders.
7. Asymmetric grating transmission functions (amplitude and/or phase) enable direction detection in all reflected orders, using appropriate signal manipulation/analysis.
8. Frequency biasing using local oscillator phase shifting, in combination with the amplitude modulation resulting from the grating at near field provide for simultaneous measurement of
2-D translation (in a transverse and axial translation plane) by a single detector.
In addition to spatial filtering related restrictions, the allowed distance between the grating and the surface generally depends on the grating period Λ, the light wavelength λ, the spectral coherence width Δλ, the illuminated area and the incident and reflected beam angles. For those preferred embodiments of the invention which utilize the light reflected or diffracted from the grating as a local oscillator, it is most preferable for the spacing between the surface 12 and the grating 16 to be smaller than the coherence length of the light, given by ∞λ2/Aλ, where Δλ is the spectral width of radiation reaching the detector, and not necessarily the spectral width of the light source. Thus, by proper spectral filtering along the optical path, the spectral content reaching the detector can be limited and its coherence length be increased, if this is necessary.
For those preferred embodiments of the invention, in which the modulated transmission pattern plays a major role in the detection scheme, the spacing between the grating and surface
12 should also be within the near-field distance from the grating, «Λ2/4λ. For the following embodiments the spacing is assumed to be near field. This requirement is relaxed for the cases where it is not essential.
Relative motion of the surface can be measured in a number of ways. Consider the incident field and the grating field transmission function, respectively: E(t) = E0cos(ω0t) (1)
A(χ) = 2jCmcos(2πmx/ Λ + ψm) (2) m
The grating is assumed to be a pure amplitude grating with period Λ, so that its transmission is the sum over non-negative spatial frequencies with real coefficients. A similar formalism applies also to binary phase grating, or some general phase gratings, which can also be used in the practice of the present invention. For the general case of both amplitude and phase gratings a phase retardation term is added. For simplicity of the description the following description is based on a pure amplitude grating. However, it should be understood that other gratings can be utilized. Unimportant constant factors are also omitted in various parts of the following mathematical treatment.
Plane-wave illumination by the light source over the grating area is assumed (i.e.- a collimated beam), but is not strictly necessary provided, for example, the non-collimation is compensated in another part of the system (e.g.- the spatial filter). It is assumed for simplicity that the incident light is peφendicular to the grating (and not as shown in Fig. 1). Oblique incident light (in the direction of the grating lines and/or peφendicular to it) gives substantially the same results, with shifted reflection angles. Thus, the grating field contains a series of reflected diffraction orders, ananged symmetrically about the specular reflection component (zeroth order) and obeying the angular condition (for the n-th order): sin(α) = nλ / Λ . (3)
As shown in Fig. 1, a spatial filter in front of the detector is preferably comprised of focusing lens 18 and narrow pinhole 20 at the focal point of the lens. Such a spatial filter is preferably adjusted to select only a single spatial frequency component to reach the detector. The pinhole can be replaced by a single-mode optical fiber, having a similar core diameter and leading the light to a remote detector. The spatial filter is aligned such that one of the diffraction orders reaches the detector, and serves as the local oscillator for homodyne detection of the reflected radiation, or for heterodyne detection as described below. The local oscillator field is given by:
ELO(t) = Encos(ω0t + Φn) ( ) The reflected field from the moving surface in the same direction as the n-th diffraction order is represented by an integral over the illuminated surface area of independent reflections from the surface. Integrating over the direction parallel to the grating lines (y) and over the direction normal to the surface (coπesponding to light penetration into the surface), results in a reflected field equal to: x2 Er(t) = E0 JdxA(x)r(x - p(t))cos(ωot +2πnx / Λ + φ(x -p(t))) (5) xi where r(x) and φ(x) are location dependent amplitude and phase reflectance of the surface, respectively. The reflectance is assumed to be time-independent during the measurement, with both r and φ being random variables of the position x. The translation of the surface from its initial position is given by p(t), with p(0)=0. The periodic phase term 2πnx/Λ arises from the reflection at an angle sin(α) = nλ/Λ. The integration limits are from x, to x2, both determined by the illuminated area. Changing the integration variable from x to x-p(t), coπesponding to the symmetric situation of a static surface and moving grating with respect to the reference coordinate system:
X2 -P(t)
Er(t) = EQ JdxA(x + p(t))r(x)cos(ωot -2πnp(t) / Λ + 2πnx/ Λ + φ(x)) (6) xι -p(t)
with integration limits now extending from xι-p(t) to X2-p(t) and thus being time-dependent. Replacing A(x) with its Fourier series and writing φn(x)=φ(x)±2πnx Λ gives: 2 -P(t) Er(t) = Eg J dx^cmcos(27πnx/ Λ + 27mιp(t) / Λ + ψm)r(x)cos(ω t + 27mp(t) / Λ + φn(x)) xi-p(t) m
(7) The (optical) phase of a scatterer on the surface linearly depends on the translation p(t), with φ=φn(x)+2πnp(t)/Λ. For specular reflection (n=0), the phase is a constant. Both the reflected field and the local oscillator field reach the detector. Since the detector measures intensity, which is proportional to the square of the field, the intensity is given by:
I(t) = (EL0(t) + Er(t))2 = EL0(t)2 + 2EL0(t)Er(t) + Er(t)2 (8)
Assuming that the local oscillator field is much larger than the reflected field, E ^Q»Er and that the detector integration time is much longer than an optical period time but much shorter than Λ/nVmax (where Vmax is the maximum measured velocity), integration over optical frequencies gives just a DC component while other variations are detected instantaneously. Under these assumptions, the first intensity term is replaced by a constant ILO=ELO2/2 and the third intensity term is neglected, i.e., Ir = Er2/2= 0. In this prefeπed embodiment of the invention, the ratio of the strength of the local oscillator field and of the reflected field is intrinsically large, since the reflection from the grating is directed only to specific narrow orders and the reflection from the diffuse surface is scattered over a broad angle.
Translation measurement utilizing the spatial transmission modulation is possible even if the third term alone is present, i.e., when the light reflected from the surface is not combined with a reference reflected or diffracted from the grating. This may be achieved (if desired) by selecting an angle which lies between grating orders. It does have the advantage of significantly relaxed alignment constrains (it is only required to be in the focal plane of the spatial filter), but will generally be less accurate and with a low signal-to-noise ratio.
The local oscillator field serves as a very strong amplifier in the first stage of signal detection. In this respect it is strongly prefeπed to keep the local oscillator field as noise-free as possible, since its noise transfers to the detected signal directly.
The measured cross term is equal to: Is(t) = Encos(ω0t + φn)Er(t) (9)
Inserting the oscillating field term cos(ωQt) into the integral for Er(t) and using the cosine sum relationship cosαcosβ=0.5(cos(α+β) + cos(α-β)) for the right-most cosine in (7), results in one intensity component at twice the optical frequency (2ωg) and another with slowly varying phase. The fast oscillating component averages to zero because of the detector's time response. The remaining signal is:
*2 -P(t) Is(t) - In I dx^cmcos(2πmx/ Λ + 2πmp(t) / Λ + ψm)r(x)cos(2πnp(t) / Λ + φn(x) -φn) xi-p(t) m
(10) Exchanging summation with integration, the contribution of each term to the sum is:
*2 -P(t) IsjinCt) = -*-ncm Jdxcos(2πmx/ Λ + 2πmp(t) / Λ + ψm)r(x)cos(27mp(t) /Λ + φn(x) -φn) xi -p(t)
(11) The grating has a period Λ. The average transmission of the grating is given by the m=0 term in the expansion. Consider the requirement that the 'zero average' grating function (function minus the zero order term) has only two zero crossings in any interval of length Λ. This requirement is equivalent to having ci > {cm, m > 1}. This last requirement enables us to concentrate on just two terms in the sum over grating harmonics, the m = 0 and m = 1 terms. For these two terms we can write:
X2 -P( Is.oW = !nc0 jdxr(x)cos(2πnp(t) /Λ + φn(x) -φn) (12) xi -p(t)
*2 -P(t) Is (t) = Incι Jdxcos(2πx/Λ + 2πp(t)/Λ + ψι)r(x)cos(2πnp(t) /Λ + φn(x) -φn) (13) χι -p(t)
Attention is now focused on specific diffraction orders in the reflected and diffracted waves from the grating, the n = 0 (specular reflection) and n = ±1 directions. For the specular reflection term, the m = 0 contribution is:
X2 -P( ISj0(t) = I0c0 Jdxr(x)cos(φ(x)) (14) xi -p(t)
For a diffuse surface with constant brightness this term will be nearly constant, and will change slowly as and when the average reflection from the surface changes. The m = 1 term is:
X2-P(t) Is l(t) = Iøci jdxcos(2πx / Λ + 27φ(t) / Λ + ψι )r(x)cos(φ(x)) = χι -p(t)
X2 ~P(t) cos(27φ(t) / Λ)IQCI Jdxcos(2πx / Λ + ψι )r(x)cos(φ(x)) - xi-p(t) (15) X2 -P( sin(27 (t) / Λ)IQCI Jdxsin(2πx / Λ + ψι )r(x)cos(φ(x)) ≡ χι -p(t) cos(2τφ(t) / Λ)Ic(t) + sin(2πp(t) / Λ)Is(t) ≡ I(t)cos(2πp(t) / Λ + θ(t))
where the intensity I(t) and phase θ(t) result from integrals over random variables coπesponding to the amplitude and phase reflection of the diffuse surface at a spatial frequency 1/Λ. For diffuse surfaces with single reflectors larger than the spatial wavelength Λ the contribution will come from grain boundaries, while for diffuse surfaces having small particle sizes there will be strong contributions for all spatial frequencies up to 1/d, where d is the average particle size.
The rate of change of these "random walk" variables depends on the average time it takes a given set of reflection centers {XJ} to be replaced by a new set, which in turn is related to the change of the integration region above, τ ∞ (xj-χ2)/v = L/v, where v is the instantaneous velocity and L is the illuminated size of the grating. If a large number of grating periods are illuminated such that L»Λ, the result is fast oscillations with a slowly varying statistical amplitude and phase. The error of the translation measurement is proportional to Λ/L and is independent of the velocity.
In summary, for specular reflection translation measurement: 1. The measured signal at the detector output oscillates at a frequency of v/Λ. Detection and counting of the zero crossing points of this signal gives a direct translation measurement, each zero crossing corresponding to a Δp=Λ/2 translation, provided that the translation direction does not change during the measurement.
2. The measured signal's amplitude and phase are slowly varying statistical ensemble sums. The relative accuracy of the measurement is proportional to Λ/L, L being the illuminated grating size.
3. The spacing between the surface and the grating should preferably be smaller than both the near field distance, «Λ*2/4λ, and the coherence length of the light reaching the detector, «λ2/Δλ. The first order reflection, unlike the specular reflection, carries also a Doppler phase shift. Looking again at the contribution of the m=0,l spatial frequency components gives:
X2 "P(t) Is,θ(t) = Iico J*dxr(x)cos(2πp(t) / Λ - φι (x) -φι) (16) χι -p(t)
X2 -P(t) ■■ts.lft) = Ilcl Jdxcos(2πx/ Λ + 2πp(t) / Λ + ψι)r(x)cos(27φ(t) / Λ + φι(x) -φι) (17) χι -p(t)
Using a decomposition of the cosine term in (16) as in (15) results in: Is rj(t) = Io(t)cos(2πp(t) / Λ + d0(t)) (18)
In a similar manner the expression for the m = 1 term, (17) is: I (t) = Iι(t)cos(4πp(t) / Λ + θι(t)) (19)
Equation (19) neglects a slowly varying term that adds to the average detector signal (the "DC" component). An analysis of equations (16)-(19) shows that if co»cι , the zero crossings of the signal correspond to Δp=Λ/2, while if co«cι, zero crossings correspond to Δp=Λ/4. This result can be expanded to other reflection orders n>l, where, if co>>cι the measured signal will oscillate according to np(t)/Λ. For |n|>l, the c term amount to oscillations in two side bands around the CQ oscillations as in amplitude modulation of a higher frequency signal. Notice that the m=0 term does not require near field conditions, so by fixing the distance to the moving surface so it is larger than the near field limit «Λ2/4λ but smaller than the coherence length «λ2/Δλ, the m=0 contribution is dominant. Alternatively, a transmission function for the grating such that co»cι even in the near field can be used.
The frequency associated with the CQ oscillations depends on the transverse as well as axial (peφendicular) translation component (not shown in the above mathematical development). Conversely, the amplitude modulation (through the c component) depends solely on the transverse component. When the frequency of the CQ oscillations is sufficiently high, this frequency can be measured by the frequency-related technique described above, simultaneously with the detection of the amplitude modulation frequency to measure the transverse translation component. In this way, 2-D translation measurement (including motion peφendicular to the plane of the surface-i.e., axial translation) may be achieved using a single detector.
By frequency biasing the reference signal, the ratio between the carrier frequency and the amplitude modulation frequency can be made large, improving the measurement accuracy as well as allowing for detection of the direction of translation. Also, using specular reflection from the grating as a local oscillator enables a clear distinction to be made between the transverse translation component (indicated by the amplitude modulation) and the axial translation component (indicated by the phase or frequency shift of the carrier frequency).
Furthermore, the phase shifting may be combined with an asymmetric transmission pattern of the grating (e.g.- sawtooth pattern) for the puφose of transverse translation direction detection. Alternatively, the grating may be displaced for direction detection in the two dimensions.
In essence, for the non-specular diffraction embodiments of the invention, two quasi- plane waves are selected for detection by the detector. One of these waves is the result of the nth order diffraction from the grating. The second plane wave is generated by the selection of one plane wave (by the spatial filter) from the reflections from the surface.
In summary for translation measurement using non-specular diffraction (and assuming constant velocity for clarity of the discussion): 1. The measured signal at the detector output oscillates at a frequency of nv/Λ, where n is the order number. Detection and counting of the zero crossing points of this signal gives a direct translation measurement, each zero crossing coπesponding to Λ/2n translation provided that the translation direction is not switched during the measurement. 2. The measured signal's amplitude and phase are slowly varying statistical ensemble sums. The relative accuracy of the measurement is proportional to Λ/nL, L being the illuminated grating size. 3. The distance between the surface and the grating should be smaller than the coherence length of the light reaching the detector, λ2/Δλ. Even though the absolute time-varying translation |p(t)| can be measured very accurately its direction is preferably determined using one of the methods described below.
In one preferred embodiment of the invention, direction may be determined by applying an additional phase shift between the reference (local oscillator) field and the reflected field. This additional phase shift can be manifested, for example, by moving the grating towards or away from the surface. This movement does not change the phase of the field incident upon the surface, so that the reflected field is identical to that given above. The local oscillator field, however, acquires an additional phase shift due to this translation that depends on the grating displacement d(t).
Keeping the distance between the grating and the surface almost constant and introducing a fixed frequency shift between the reflected and local oscillator fields can be achieved by making d(t) a periodic saw-tooth function: t OO dn(t) = Dn J[τ"1 - ∑δ(f-kτ)]df
0 k=0
(20) λ
Dn =
1-H/1 - , nλ ,,A) with τ as the cycle time for the saw-tooth, fixing the amplitude of the saw-tooth to give 2π phase shift (or multiples of 2π) for reflection at the nth diffraction order. The frequency shift due to this motion is τ"l, and if τ"l > nv/Λ is maintained, the direction of the motion is determined without ambiguity according to the frequency of oscillation of the detector signal, namely τ"l+nv/Λ. Alternatively, the translation (both positive and negative) is determined directly by counting the zero crossing in the detected signal and subtracting it from the result of a simultaneous count of the oscillator frequency τ"l. If the saw tooth amplitude is not ideal, (i.e., it does not correspond to integer multiples of the wavelength) the direction can still be determined, however, the formulation is more complicated. As used herein, the term "saw-tooth" includes such non-ideal variations.
An alternative way of introducing a periodic phase shift between the local oscillator field and the field reflected from the surface is to modulate the optical path length between the grating and the surface. This is preferably achieved by a transparent piezo-electric element mounted between the grating and the surface.
An alternative methodology to break the symmetry between positive and negative relative translation, so that the translation direction can be detected, is to use an asymmetric function for the transmission (amplitude and/or phase) function of the grating. For simplicity, the formalism is developed for an amplitude grating. For simplicity, assume that the grating is large compared to the line spacing along the translation axis and that k point scatterers are illuminated through the grating. Scatterers entering or leaving the illuminated area are neglected
(this will appear as a noise factor in a comprehensive treatment). After the interference with the local oscillator (which is not shifted here) and filtering the optical frequencies, the resulting signal can be written as: k Is(t) = In ∑ηA(xi + p(t))cos(2πnp(t) / Λ + φi) (21) i=l where rj, { and φ-f are the reflectance, the position (at time t*=0) and the relative phase (with respect to the local oscillator), respectively, of a scatterer i. For a diffuse body these are all random variables. This presentation of the detector signal is used for the following direction- detection mechanisms.
For specular reflection: k Is ) = Iθ ∑riA(xι + p(t))cos(φi) (22) i=l Assuming that p(t) = vt . i.e.- changes in the surface velocity are relatively small during the integration time used for determination of the translation direction. Thus, the first and second derivatives of the received signal are: k d
Is(t) = Iov∑ricos(φi)— (A(Xi + vt)) (23) i=l k d2 l's( = IQ 2 ∑ηcos φi (A(Xi + vt)) (24) i=l dx , , d2A(x) dA(x) Assume that A(x) is constructed such that — = η — . In this special case it is dx2 dx
II I evident that: Is(t) = ηv- Is(t) . Thus, the magnitude, and more importantly, the sign of the translation velocity (i.e.- the translation direction) can be derived from the ratio between the first and second time-derivatives of the detector signal. If the velocity cannot be assumed to be constant during the direction-decision integration time, then the derivatives may be performed with respect to the measured translation (which is known from the zero-crossing or from another detector with higher accuracy operated in parallel). If only the direction is required (and not the velocity magnitude), it is sufficient to check if the first and second derivatives carry the same sign (one direction) or not (opposite direction). A simple XOR (exclusive OR) operation after sign-detection of the derivatives will be "1" if the sign of η is opposite to the sign of v and "0" if they are the same.
An example of A(x) that satisfies the constant derivative ratio is a combination of exponents like:
A(l-e~^x ~ Λ) / Λ): if jΛ < x < Λ(j + l/2)
A(x) = (25)
A(e- γ(x - (j + l / 2)Λ) / Λ _ e-γ / 2): if Λ(j + l/2) < x < Λ(j + 1)
where the pattern is repetitive with a cycle Λ. It is evident that for this pattern the first and second (and in fact all) derivatives have a constant ratio as required, of η = -γ / Λ . But, the singularity points in multiples of Λ/2 introduce "noise" to the measurement. These singularities increase the eπor probability as the number of scatterers grow, since each one will appear in the received signal when a scatterer passes across it. The relative noise contribution is reduced as the direction detection integration time increases.
The pattern is assumed to be the intensity of illumination on the surface. Thus, the requirement for the near field is more stringent than the similar requirement for measuring translation magnitude alone in n=0 specular reflection. An assumed transmission pattern is shown in Fig. 2, for γ=5. This can be achieved by having a partially reflecting/transmitting property for the grating, having an amplitude transmission function such as that shown in Fig. 2.
A relaxed requirement from the transmission pattern is that the derivatives will have a constant sign relationship (i.e.- they are not exactly proportional, but their ratio's sign is constant along the pattern). Here, direction-detection is still assured for a single scatterer, but the eπor probability is higher than in the former case as the number of scatterers gets larger (even without the effect of the singularities).
A similar analysis is possible for high-order reflection (|n|»l). Again, for simplicity the surface is assumed to move with a constant velocity, v. Equation (21) can be looked at as a sum of amplitude-modulated signals of a carrier with frequency nv/ Λ . A(x) is now assumed to be asymmetric (e.g.- sawtooth waveform). For |n|»l, the detector's signal envelope matches the transmission function for translation in the "positive" direction and is the inverse image the other way. Thus, if the number of scatterers is small (the limit being dependent on the grating order n), the translation direction is represented by the sign of the first derivative of the detected signal's envelope (and in addition, the magnitude of the envelope derivative is proportional to the magnitude of the translation velocity).
An asymmetric transmission pattern enables direction detection for speckle velocimetry.
The detector signal resulting from a random speckle pattern, filtered by a grating with intensity transmission pattern A(x) adjacent to the detector, can be represented as: k Is(t) = Iθ ∑r.A(xi + p(t)) (26) i=l where r*: and x[ are the intensity and position of the i-th "speckle", respectively, and p(t) the surface translation. Assuming constant velocity, p(t)=vt, the detector signal time derivative is: k d Is(t) = Iθ ∑ri — (A(xi + vt)) (27) i=l
The intensities η are positive values. Thus, if dA/dx is constant, then the derivative of the detector signal is indicative of the translation direction. Such a pattern is accomplished using sawtooth transmission pattern. The discontinuities in the pattern add noise to the measurement, requiring the use of an appropriate integration interval in order to limit the eπor probability. The motion velocity is determined from the frequency of oscillations of the detector signal.
Of course, it is possible to utilize mechanical or other means (e.g.- an accelerometer) to determine the direction of motion as a complementary component in an OTM device.
As was noted above, fluctuations in the source amplitude are directly transfeπed to the received signal via the local oscillator field. In order to minimize such noise, in accordance with a prefeπed embodiment of the invention, a signal proportional to the source amplitude is detected and the resulting signal (termed the "compensation" detector and signal) is subtracted from the detector signal. This detection can be performed, for example, by: • Splitting the source beam with a beamsplitter (which need not be accurately aligned) and directing the diverted beam to the compensation detector, or
• Directing any of the light beams reflected from the grating to a compensation detector without spatial-filtering it (but potentially with considerable attenuation). Conveniently this may be one of the grating orders not used for the spatial filter measurement, e.g.- use order
1 for spatial filter and order 0 for source-noise compensation.
The output of the compensation detector is amplified (or attenuated) so that the resulting difference signal is as close to zero as possible when the surface is not moving relative to the device (or when the "window" is closed with an opaque cover), thus compensating for the EQ2 factor.
In order to compensate for the EQ multiplier of the Er component, the signal from the compensation detector may be the control voltage of a gain-controlled amplifier in one of the stages of the signal amplification (after the first compensation by subtracting the EQ2 component), where the gain should be approximately proportional to the inverse of the square- root of the compensation signal.
Fig. 3 A shows a prefeπed implementation of a translation detector, in accordance with a prefeπed embodiment of the invention, in which zeroth order detection is used and which does not incoφorate direction detection, or in which the detection of the direction is based on an asymmetric grating transmission pattern and appropriate signal analysis. Fig. 3A shows an integrated optical chip translation device 30 which is suitable for mass production. It utilizes only a few components that can be manufactured in large quantities for a low price. Device 30 comprises a laser diode 32, preferably a single transverse mode laser. Laser light from laser diode 32 is preferably collimated by a lens 34, which is preferably a diffractive collimating lens, etched into or deposited onto the surface of an optical chip substrate 36 of glass, quartz or the like, preferably coated with reflective layers on both sides other than in designated areas. A grating 38 preferably, either an amplitude or phase type grating is mounted on optical chip substrate 36. Grating 38 is preferably etched or deposited onto the lower surface of substrate 36. Light reflected by the grating and light reflected from a surface 42 is reflected by two reflective surfaces 40 and 41 and focused by a lens 44, preferably a reflective diffractive focusing lens, etched into the surface of optical chip substrate 36. After further reflection by a reflective surface 45, a pinhole 46, formed in a reflective/opaque layer formed at the focus of lens 44, passes only a plane wave from surface 42 and the reflected light from grating 38 to a detector 50, for example a PIN photo diode or similar device. A compensating detector 52 is preferably placed behind lens 44 detects a portion of the light reflected by grating 38. A controller 54, comprising a laser diode driver/modulator for activating laser diode 32, detection amplifiers and zero crossing counting circuits or frequency detection means used for determining the translation velocity and translation of the surface. Compensation detector supplies a compensation signal proportional to the amplitude of the local oscillator for reducing any residual effects of variations in the laser output. For reduction of noise, twisted wire pairs, shielded wires or coaxial cable are preferably used to carry signals to and from controller 54. Preferably, the apparatus is provided with legs or a ring support 56 or other such means on which the device rides on surface 42 to avoid damage to grating 38 and to keep the distance between the grating and the surface fairly constant.
Fig. 3B shows an alternative prefeπed embodiment of the invention including direction detection by phase shifting of the local oscillator and utilizing first order diffraction from the grating. Elements which are functionally the same as those of Fig. 3B are given the same reference numerals in both Figs. 3A and 3B. Fig. 3B shows a device 60 in which light from laser diode 32 is collimated by a lens 62 to strike a grating 38. Grating 38 is preferably mounted on a piezoelectric ring 64 (which is in turn mounted on optical substrate 36). Excitation of ring 64 adds a variable phase to the local oscillator (the light diffracted from grating 38) in order to allow for direction detection, as described above. In the embodiment shown in Fig. 3B, both the detection of the signals used for translation and direction detection on the one hand and for compensation detection on the other hand, are based on first order diffraction by grating 38, but with opposite sign. Preferably, anti-reflection coatings are used, where appropriate, to reduce unwanted reflections.
Fig. 3C shows yet another method of determining direction, in accordance with a prefeπed embodiment of the invention. This device is similar to the device of Fig. 3B except that grid 38 is placed at the lower surface of chip 36 and piezoelectric ring 64 is replaced by a birefringent plate 66. Source 32 produces linearly polarized light having a polarization which is at an angle of 45 degrees with the birefringent axis of plate 66. Radiation which is reflected from the surface passes through plate 66 twice and consists of two waves, each having a polarization direction at a 45 degree angle with that of the radiation reflected from or diffracted from grating 38. These waves are also at substantially a 90 degree phase difference with each other (depending on the properties of the surface).
In addition, a polarizing beam splitter 68 is preferably placed before detector 50. Its axis is such that one of the two halves of the reflected radiation passes through beam splitter 68 to detector 50 and the other half is reflected to a detector 67. In addition, beam splitter 68 directs half the radiation reflected or diffracted from grating 38 to each of detectors 50 and 67. The resulting signals detected by detectors 67 and 50 will have a phase difference of 90 degrees. The sign of the phase difference can be used to determine the direction of motion. An integrated optical chip is the prefeπed implementation scheme since it can be manufactured in large volumes for a low cost. The figure shows only one detector for a single direction, with preferably a second detector measuring the orthogonal direction. All of the optical elements - lenses, grating, minors and pinholes - are etched into or deposited onto the optical substrate and are either reflective or transmissive according to functionality. The discrete components in the system - laser diode, detector and piezoelectric transducer- are mounted on top of the chip. The electronic elements of controller 54 may also be manufactured or placed on top of the chip.
It should be understood that the features of Figs. 3A and 3B can be mixed and combined. For example if, in Fig. 3 A, grating 38 is mounted on a transducer such as ring 64, then the result would be a device operating in the specular reflection (zeroth order) mode with increased dynamic range and possibly additional axial translation detection. Furthermore, it is possible to use an asymmetric grating in place of grating 38 and ring 64 of Fig. 3B for the puφose of direction detection. For these and other prefeπed embodiments of the invention, combining various aspects of the invention will occur to persons skilled in the art. While the present invention is described above in various embodiments for solving the general problem of translation measurement, the methodology is applicable to a large number of products. One particular application of the optical translation measurement method of the invention is a novel optical cursor control device (mouse) which derives its translatatory information from movement on substantially any diffuse surface, such as paper or a desktop. One design for such a device, in accordance with a prefeπed embodiment of the invention, is shown in Fig. 4. An optical mouse 80 comprises an "optical chip" 82 which is preferably a device such as device 30 or device 60 or a variation of these devices. Chip 82 is mounted in a housing 84 and views paper 42 through an optical aperture 86 in housing 84. Input and output leads from chip 82 are preferably connected to a printed circuit board 88 or the like on which are mounted electronic circuitry 90 coπesponding to the controller of devices 30 or 60. Also mounted on PC board 88 is one or more switches 92 which are activated by one or more pushbuttons 94 as in conventional mice. The mouse is conventionally connected to a computer via a cable 96 or with a wireless connection. The method of measurement in accordance with preferred embodiments of the invention described above allows for a wide dynamic range of translation velocities, covering all the required range for normal operation of a mouse. Such a device can be characterized as a 'padless optical mouse' to provide orthogonal signals to move a cursor from position to position on a display screen in response to movement of the mouse over any sufficiently diffusely reflective surface, such as paper or a desk top. Thus, special contrasting markings or special patterns are not necessary.
Mouse systems usually use mechanical transducers for the measurement of hand translation over a surface (commonly a "mouse pad"). A need for moving-parts-free, reliable and accurate translation measurement technology for use in mouse systems is well acknowledged today. A few optical devices were developed, but still suffer from various deficiencies, such as a need for a dedicated patterned pad, low transducing performance or high cost.
An optical padless mouse according to one preferred embodiment of the invention can be used in two ways, according to the user's convenience. It can be used as a "regular" mouse, whereby the mouse is moved on top of a surface, and its motion relative to that surface is measured. It can also be flipped over, if so desired, and instead used by moving the finger along the device aperture. The motion of the finger relative to the mouse body, which is now stationary, will be measured. One such device 100 is shown in Figs. 5 A and 5B. Fig. 5 A shows that structurally the device is similar to that of Fig. 4 (and the same reference numbers are used in the two Figs, for ease of comparison), except that buttons 94 are on the side of housing 84 in device 100. In the mode shown in Fig. 5 A device 100 is stationary and it is used to track the movement of finger 102 of an operator. It should be clear that device 100 can be turned over and used as a mouse, in much the same way as the mouse of Fig. 4. Fig. 5B shows a perspective view of the device, showing an optional switch 104 which is used to indicate if device 100 is used as an ordinary mouse or in the mode shown in Figs. 5 A and 5B. Alternatively, such a switch may be a gravity switch mounted in the device to automatically switch modes. It is generally desirable to know in which mode the device is operating since the direction of motion of the cursor is opposite for the two modes and usually, the sensitivity desired is different for the two modes.
Furthermore, using a translation measurement device with a small aperture, as in the present invention, and moving a finger along its aperture, enables moving a cursor through measurement of the translation of the finger, much like a touch pad. This function may be termed "touch-point" and may be used in dedicated minute locations on keyboards as well. This device would be identical to the device of Fig. 5 except that the optical chip would be mounted in the keyboard as would the switches. Also, an OTM "touch-point" may be used on the top of the mouse as an alternative to a scrolling wheel. "Clicks" may be detected, for example, by bringing the finger into and out of range of the touch point.
This device can be used to replace pointing devices other than a mouse. For example, pointing devices used in laptop or palmtop computers. Virtually any one or two dimensional motion can be controlled using such a device.
Cuπently, laptop computers pointing devices employ either a track ball, a touch pad, a trackpoint (nipple) or an attached mouse. These devices carry diverse drawbacks. In particular, the track ball collects dust much like a regular mouse, the touch pad is sensitive to dampness and was hailed unfriendly by many users, the trackpoint drifts when it should be idle and the attached mice are delicate and require a desktop to work on.
The touch-point device is small in size, its working aperture can be less than 1 mm2 and it provides high resolution and dynamic range. This makes it an ideal solution as a pointing device to be embedded in a laptop computer. The device is operated by moving a fmger across the face of the aperture, in a somewhat similar manner to the use of a touch pad. The difference being, that the aperture is very small in size compared to the touch pad, it is free of problems like humidity and dampness and its reliability is expected to be high. In fact, even several devices can be easily embedded in a single laptop or a palm top, including on keys, between keys, or next to the screen. Additionally, a pressure sensitive device may be included under the touch point device and the sensitivity of the touch point made responsive to the pressure of the fmger on the touch point.
In a prefeπed embodiment of the invention, two touch points are provided, a first touch point and circuitry which moves a pointer responsive thereto and a second touch point and circuitry which causes scrolling responsive thereto.
In a further prefeπed embodiment of the invention, the present invention can be used as an improved translation and/or velocity measurement system for a scanning-pen, capable of scanning lines of text (or any other pattern) and storing them, for downloading later to a PC, and/or for conversion to ASCII code using OCR software. An example of such a device is shown in Fig. 6. A scanning pen 120 comprises a 'reading' head with a one dimensional or two dimensional array of photo detectors (CCD aπay) 122 and a lens 123, wide enough to scan a typical line height, and a lighting source 124 as in conventional light pens. The pen head also contains an optical translation measurement system 82 in accordance with the invention, for one or two axes measurement of the translation of the pen head across the scanned paper and possibly another one to extract rotation information. The pen can then either store the scanned line as a bitmap file (suited for hand-writing, drawings etc.) or translate it immediately through using internal OCR algorithm to binary text. The stored information may be downloaded later to a computer, palmtop or phone, etc. For this puφose and for the powering and control of the various devices in pen 120, it is provided with a controller or microprocessor 128 and batteries 129.
The optical translation method of the present invention allows for this device to be small in size, convenient to use, and accurate. The high accuracy results from the inherent high accuracy of the method with respect to current mechanically-based translation transducers and from the ease of measurement in two dimensions plus rotation. Similar commercial devices today use a patterned wheel which is pushed against the scanned surface while scanning and rolled in order to measure the translation by detecting the rolled angle of the wheel. This technique only detects the location along the line and not along its vertical axis and its relatively low accuracy limits the range of applications it can be used for.
A further preferred application of the optical translation method and device of the present invention is a portable or a fixed device, for scanning signatures and relaying them to an authentication system. Similar in principal to the scanning pen, the signature reader contains a 'reading' head, with a one dimensional or two dimensional array of photo detectors (CCD array), it has an aperture wider than that of the scanning pen, to be able to read wider or higher signatures and contains an optical translation measurement device, for detection of the two axes translations of the hand or instrument which is moving the device across the scanned signature. The signature reader does not contain any OCR, as no text files are to be created. Instead, it is connected (through direct, hardwire line or wireless link, or through an off-line system), to an "authentication center", where the scanned signature is compared to a "standard signature" for validation. This device can be accurate, while cheap, small and easy to use.
A still further application of the devices and methods described above is in the field of encoders. The present invention can replace linear encoders and angular encoders, which generally require highly accurate markings on either an encoder wheel or on a surface, by a substantially markless encoder. An angular encoder 130 in accordance with this aspect of the invention is shown in Fig. 7. Encoder 130 comprises a disk having a diffusely reflecting surface 132 mounted on a shaft 131. It also includes an optical chip 82 and controller 90, preferably essentially as described above. Preferably, surface 132 is marked with one or two radial marks 136 to act as reference marks for the encoder and for correction of errors which may occur in reading the angle during a rotation. This mark may be read by chip 134 which may be provided, for this puφose, with a simple reflection detector which detects the passage of line 136. Alternatively, the same detector may be used for motion detection and detection of the marker. A further embodiment of the invention is a virtual pen, namely a pen which translates movement across a featureless page into position readings. These position readings can be translated by a computer into virtual writing which can be displayed or translated into letters and words. The computer can then store this virtual writing as ASCII code. Transfer to the computer may be either on line (using a wired or preferably a wireless connection to the computer) or off-line wherein the code or positions are stored in the "pen" and transfeπed after writing is completed. This embodiment of the invention provides a compact, paper-less and voice-less memo device.
In a typical fax/printer, the paper is moved in a constant speed relative to the writing head with an accurate motor. The head releases the printed data line by line, in a coπelated fashion with the speed of advancing paper. This method is both expensive, as it requires an accurate motor and mechanical set up, and inaccurate, as the paper sometimes slips in the device, thus the paper translation is not well coπelated to the printing device, resulting in missed or crooked lines. With an optical translation measuring device, it is possible to detect paper slippage, or even to eliminate the use of expensive accurate motors, by measuring the paper advancement on-line. The printing device is then coordinated with the actual translation of the paper, thus creating a highly accurate and economic system. Similarly, these principles can be applied to a desktop scanner, where the printing head is replaced by a reading head. Fig. 8 is a schematic of a motion sensor useful in a scanner, fax machine or printer in which motion is only in one direction. Motion detector 200 includes a source 202 which is fed to a housing 204 by a fiber optic cable 205. The output of cable 204 is collimated by lens 206 and illuminates a moving surface 208, through a grating 210. Light reflected from grating 210 and surface 208 is collected by a fiber optic cable 212 which is placed at the focal point of lens 206. The output of cable 212 is fed to a detector 214, for further processing as described above. Since the paper moves in only one direction, there is no need to detect the direction of motion of the paper.
In a preferred document scanner embodiment of the invention, the motion detector measures the relative movement of a document, preferably, without utilizing any printing on the document, while a reading head reads printed information from the document. A memory receives information from the printing head and stores it in memory locations, responsive to the measurement of movement of the document. In a prefeπed printer embodiment of the invention the motion detector measures the movement of a sheet on which markings are to be made and a memory transmits commands to mark the paper, in accordance with information in the memory, responsive to the measurement of motion of the paper.
Either or both prefeπed scanner and printer embodiments of the invention may be utilized in a facsimile machine in accordance with prefeπed embodiments of the invention.
Fig. 9 is a simplified block diagram of typical electronic circuitry 140 useful in carrying out the invention. A "primary" photodetector 142 (corresponding, for example to detector 50 of Figs. 3A and 3B) receives light signals as described above. The detector detects the light and the resulting signal is preferably amplified by an amplifier 144, band pass filtered by a filter 146 and further amplified by an amplifier 148 to produce a "primary" signal. A compensating signal as detected for example by photodetector 150 (coπesponding to detector 52 in Figs. 3 A and 3B) is subtracted (after amplification, by amplifier 152 and band-pass filtering by filter 154) from the "primary" signal in a difference amplifier 155 to remove residual low frequency components in the primary signal. Preferably, band pass filters 154 and 146 are identical. The resulting difference signal is amplified by a voltage controlled amplifier 156 whose gain is controlled by the output of a low pass filter 153 (which is attenuated by an attenuator 158 optionally adjusted during calibration of the system). The output of amplifier 156 is fed to a zero crossing detector and counter 160 and (if a stationary non-symmetric grating is used) direction control logic 162, which determine the direction of translation of the surface. Alternatively, where a piezoelectric element 64 (Figs. 3A and 3B) is used, a control signal corresponding to the frequency of displacement of the of the element is fed to the direction control logic 162 where it is subtracted from the zero-crossing detector count.
For preferred embodiments of the invention, the wavelength of the laser source is preferably in the infra-red, for example 1550 nanometers. A spectral width of 2 nanometers is typical and achievable with diode lasers. A source power of 5 mW is also typical. A grating opening of 1.5 mm by 1.5 mm and a grating period of 150 lines/mm are also typical. The laser source output is typically collimated to form a beam having a diameter of somewhat less than 1.5 mm and is typically incident on the grating at an angle of 30 degrees from the normal. The optical substrate may have any convenient thickness. However a thickness of several mm is typical and the focal length of the lenses used is designed to provide focusing as described above. Typically, the focal length of the lenses are a few mm. Typically, pinhole 46 (Figs 3A and 3B) has a diameter of several micrometers, typically 10 micrometers. It should be understood that the above typical dimensions and other characteristics are provided for reference only and that a relatively wide variation in each of these dimensions and characteristics is possible, depending on the wavelength used and on other parameters of the application of the optical chip.
The present invention has been described in conjunction with a number of prefeπed embodiments thereof which combine various features and various aspects of the invention. It should be understood that these features and aspects may be combined in different ways and various embodiments of the invention may include one or more aspects of the invention. The scope of the invention is defined by the following claims and not by the specific prefeπed embodiments described above.

Claims

1. A method for determining the relative motion of a surface with respect to a measurement device, comprising: placing a partially transmitting object as part of the measuring device, adjacent to the surface; illuminating the surface with incident radiation such that the radiation is reflected from portions of the surface towards a detector, wherein at least part of at least one of the incident and reflected radiation passes through the object; detecting the radiation reflected from the surface, such that the detector generates a signal; and determining the relative motion of the surface parallel to the surface, from the detected signal.
2. A method according to claim 1 wherein the transmission of the object is spatially varying.
3. A method according to claim 1 or claim 2 wherein the object is partially reflecting and wherein part of the incident radiation is reflected or diffracted by the object towards a detector, as a reference radiation and wherein detection of the radiation is coherent, utilizing said reference radiation.
4. A method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface with incident radiation such that the radiation is reflected from portions of the surface towards a detector; placing a partially reflecting object, which is part of the measuring device, adjacent to the surface, wherein part of the incident radiation is reflected or diffracted by the object towards the detector, as a reference radiation; coherently detecting the radiation reflected from the surface utilizing the reference radiation, such that the detector generates a signal; and determining the relative motion of the surface parallel to the surface, from the detected signal.
5. A method according to claim 4 wherein the reflection of the object is spatially varying.
6. A method according to claim 2 or claim 5 wherein spatially varying comprises periodic spatial variation.
7. A method according to any of claims 4-6 wherein the object is a partially transmitting object and wherein at least part of at least one of the incident and reflected radiation passes through the object.
8. A method according to any of the preceding claims wherein placing an object adjacent to the surface comprises: placing a grating adjacent to the surface.
9. A method according to claim 8 wherein placing a grating adjacent to the surface comprises: placing the grating sufficiently close to the surface such that the surface is in the near field of the grating.
10. A method according to claim 8 wherein placing a grating adjacent to the surface comprises: placing the grating sufficiently far from the surface such that the surface is outside the near field of the grating.
11. A method according to any of the preceding claims wherein the detected radiation is at least partly coherent.
12. A method according to any of the preceding claims wherein the object and the surface are situated within a distance which is less than the coherence length of the radiation which reaches the detector.
13. A method according to any of the preceding claims wherein the radiation reflected from the surface is frequency shifted from that of the radiation reflected from or diffracted by the object and wherein determining the motion comprises determining the motion based on the frequency shift.
14. A method according to any of the preceding claims wherein determining the motion comprises determining variations in the amplitude of the signal with position.
15. A method according to claim 14 wherein the motion is determined from zero crossings of the detected signal.
16. A method according to any of the preceding claims wherein the object has a transmission characteristic that is spatially non-symmetric.
17. A method according to claim 16 and including: determining the direction of the relative motion based on a characteristic of the signal caused by said non-symmetry.
18. A method for determining the relative motion of a surface with respect to a measurement device comprising: placing a partially transmitting object, which is part of the measuring device, adjacent to the surface; illuminating the surface with incident radiation such that the radiation is reflected from portions of the surface towards a detector, wherein at least part of at least one of the incident and reflected radiation passes through the object; detecting the radiation reflected from the surface, such that the detector generates a signal; and determining the relative motion of the surface parallel to the surface, from the detected signal.
19. A method according to any of the preceding claims and comprising: varying the phase between the radiation reflected from or diffracted by the object and at least a portion of the radiation reflected from the surface.
20. A method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface with incident radiation such that radiation is reflected from portions of the surface and such that radiation is reflected from or diffracted by the object toward a detector; placing a partially reflecting object, which is part of the measuring device, adjacent to the surface, wherein part of the incident radiation is reflected or diffracted by the object towards the detector, as a reference radiation; coherently detecting the radiation reflected from the surface, utilizing the radiation reflected from or diffracted by the object as a local oscillator, to form a signal; determining the relative motion of the surface from the signal; varying the phase of the radiation reflected from or diffracted by the object with respect to that reflected from the surface; and determining the direction of relative motion parallel to the surface based on a characteristic of the signal caused by said varying relative phase.
21. A method according to claim 20 wherein placing a reflector adjacent to the surface comprises: placing a grating adjacent to the surface.
22. A method according to any of claims 19-21 wherein varying the phase comprises periodically varying the phase.
23. A method according to claim 22, wherein determining the direction of relative motion comprises determining the direction of relative motion based on a characteristic of the signal caused by said varying relative phase.
24. A method according to any of claims 19-23 wherein varying the phase comprises: causing the object to move periodically substantially in the direction of the motion being measured.
25. A method according to any of claims 19-24 wherein varying the phase comprises: causing the object to move periodically substantially peφendicularly to the direction of the motion being measured.
26. A method according to any of claims 19-25 wherein varying the phase comprises: providing a transparent material between the object and the surface; and electrifying the material such that its optical length in the direction of the radiation varies.
27. A method according to claim 26 wherein the transparent material is a piezoelectric material.
28. A method according to any of claims 18-27 and including determining both the magnitude and direction of the translation utilizing a single detector.
29. A method according to any of claims 19-21, wherein varying the phase comprises, introducing a static phase change and wherein determining the direction of relative motion comprises determining the direction of relative motion based on a characteristic of the signal caused by said phase change.
30. A method according to any of claims 19-29 and including: dividing the radiation that is reflected from the surface into a first radiation having a first phase and a second radiation having a second phase.
31. A method according to claim 30 wherein said first and second radiations have different polarizations.
32. A method according to claim 31 wherein dividing comprises passing the radiation incident on the surface through a birefringent material.
33. A method according to claim 31 or claim 32 and including passing the radiation reflected from the surface through the birefringent material.
34. A method according to claim 32 or claim 33 and including placing the birefringent material between the object and the surface.
35. A method according to any of claims 29-34 and including determining the direction of translation from the sign of the phase difference between the first and second radiations.
36. A method according to any of claims 18-27 or 29-35 and including determining the magnitude and direction of the translation utilizing two detectors which produce different signals depending on the direction of the translation.
37. A method for determining the relative motion of a surface with respect to a measurement device comprising: placing an apertured reflector, which is part of the measurement device, adjacent to the surface; illuminating the surface with incident radiation such that radiation is reflected from portions of the surface and such that radiation is reflected from or diffracted by the apertured reflector toward a detector; coherently detecting the radiation reflected from the surface utilizing the radiation reflected from or diffracted by the apertured reflector as a local oscillator to form a signal; determining the relative motion of the surface peφendicular to and parallel to the apertured reflector from the signal.
38. A method according to claim 37 wherein: coherently detecting comprises: detecting amplitude or phase variations of the reflected radiation; and detecting a frequency shift of the reflected radiation; and determining the relative motion comprises: measuring relative motion of the surface in a direction parallel to the apertured reflector responsive to at least one of the detected amplitude or phase variations; and measuring relative motion of the surface in a direction peφendicular to the surface of the apertured reflector responsive to the detected frequency shift.
39. A method according to claim 38 and comprising: periodically moving the apertured reflector surface in a direction peφendicular to its surface to add a periodic phase shift to the radiation reflected therefrom; and utilizing said phase shift to measure the motion of the surface.
40. A method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface, from a source, with incident radiation such that radiation is reflected from portions of the surface toward a detector; spatially filtering the reflected radiation such that the phase of the optical radiation exiting the spatial filter from a given scatterer on the surface is substantially constant or linearly related to the translation of the surface; generating a signal by the detector responsive to the radiation incident on the detector; and determining the relative motion of the surface from the signal.
41. A method according to claim 40 wherein illuminating comprises illuminating the surface with spatially varying radiation.
42. A method according to claim 40 or claim 41 wherein illuminating the surface comprises illuminating the surface through an apertured reflector placed adjacent to the surface which reflects or diffracts radiation to the detector.
43. A method according to claim 42 wherein generating a signal comprises coherent detection of the radiation reflected from the surface utilizing the radiation reflected or diffracted from the apertured reflector.
44. A method according to any of claims 40-43 wherein determining the relative motion comprises utilizing a Doppler shift of the reflected radiation.
45. A method according to any of claims 40-44 wherein: the illumination of the surface is substantially collimated; and the spatial filter filters the reflected illumination such that substantially only a single spatial frequency of the reflected radiation is incident on the detector.
46. A method according to any of claims 40-44 wherein: illumination of the surface is substantially collimated; and spatial filtering filters the reflected illumination such that only radiation reflected from the surface substantially in a single direction is incident on the detector.
47. A method according to any of claims 40-46, wherein spatial filtering comprises: focusing the reflected radiation with a lens having a focal point; and placing a pinhole at the focal point of the lens.
48. A method according to any of claims 40-46, wherein spatial filtering comprises: focusing the reflected radiation with a lens having a focal point; and placing a single mode optical fiber at the focal point of the lens to transfer radiation to the detector.
49. A method according to claims 40-46, wherein spatial filtering comprises: focusing the reflected radiation with a lens; and placing a pinhole at an image of the source.
50. A method according to claims 40-46, wherein spatial filtering comprises: focusing the reflected radiation with a lens; and placing a single mode optical fiber at an image of the source to transfer radiation to the detector.
51. A method for determining the relative motion of a surface with respect to a measurement device comprising: placing an object, having at least a quasi-continuous transmission function, adjacent to the surface; illuminating the surface with incident radiation such that radiation is reflected from portions of the surface toward a detector; detecting the radiation reflected from the surface utilizing the detector to generate a signal; and determining the relative motion of the surface from the signal.
52. A method according to claim 51 wherein the object has an asymmetric transmission function; and wherein determining the relative motion comprises determining the direction of motion based on the detected signal.
53. A method according to claim 51 or claim 52 wherein: radiation is reflected from or diffracted by the apertured reflector toward the detector; and said detection is coherent detection utilizing the radiation reflected from or diffracted by the apertured reflector as a local oscillator to form a signal.
54. A method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface with incident visible or infrared radiation such that radiation is reflected from the surface to illuminate a detector with radiation which is not an image of a point on or a portion of the surface; simultaneously illuminating the detector with reference radiation derived from said incident radiation; coherently detecting the reflected illumination of the detector utilizing said reference radiation such that the detector generates a signal; determining the relative motion of the surface parallel to the surface, based on variations of the signal with time.
55. A method according to claim 54 wherein the incident radiation is at a given wavelength and wherein the reference radiation is at the same wavelength such that the coherent detection is homodyne detection.
56. A method according to claim 54 or claim 55 and comprising: spatially varying the illumination of the surface.
57. A method according to claim 56 wherein spatially varying the illumination of the surface comprises: illuminating the surface through an apertured reflector.
58. A method according to claim 56 or claim 57 wherein spatially varying the illumination of the surface comprises: illuminating the surface through a transmission grating having spatially varying periodic transmission.
59. A method according to claim 56 wherein spatially varying the illumination of the surface comprises: illuminating the surface through a grating which specularly reflects a portion of the radiation incident upon it toward the detector to form said reference radiation.
60. A method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface with visible or infrared radiation such that radiation is reflected from portions of the surface toward a detector; coherently detecting the radiation reflected from the surface; and determining the relative motion of the surface, in a direction parallel to the surface, from a characteristic of the signal based on a Doppler shift of the reflection reflected from the surface.
61. A method according to claim 60 and including: placing an apertured reflector adjacent to the surface, wherein said coherent detection utilizes radiation reflected from or diffracted toward the detector from the apertured reflector as a local oscillator.
62. A method according to claim 61 wherein the apertured reflector is a grating and wherein radiation diffracted by the grating is used in determining the motion.
63. A method according any of the preceding claims wherein the illumination is peφendicularly incident on the surface.
64. A method according to any of the preceding claims wherein the surface is optically diffusely reflecting surface.
65. A method according to any of the preceding claims wherein the surface has no markings indicating position.
66. Apparatus for determining the relative motion of a surface and the apparatus, comprising: a partially transmitting object situated adjacent to the surface; a source of radiation which illuminates the surface with incident radiation such that radiation is reflected from portions of the surface towards a detector, wherein at least part of at least one of the incident and reflected radiation passes through the object; a detector which detects the reflected illumination such that the detector generates a signal; and circuitry which determines relative motion of the surface parallel to the surface with respect to the apparatus from the detected signal.
67. An optical mouse comprising: a housing having an aperture facing a surface; and an optical motion detector which views the surface through the aperture, wherein the optical motion detector utilizes the method of any of claims 1-65 to determine the translation of the housing with respect to the surface.
68. A touch point for use as a control device, comprising: a housing having an aperture; and an optical detector which determines the motion of a fmger which is translated across the aperture.
69. A touch point according to claim 68 wherein the optical detector utilizes the method of any of claims 1-65 to determine the translation.
70. A pointer device comprising: a first touch point according to claim 68 or claim 69 and circuitry which moves a pointer responsive thereto; and a second touch point according to claim 68 or claim 69 and including circuitry which causes scrolling responsive thereto.
71. A combination mouse/touch point for use as a pointer for a computer comprising: a housing having an aperture; an optical detector which determines the motion of an object which is translated across the aperture; and means for determining whether the aperture is upward or downward facing.
72. A combination mouse/touch point according to claim 71 wherein the optical detector utilizes the method of any of claims 1-65 to determine the translation.
73. A scanner for reading a document by movement of the scanner over the document comprising: an optical reading head which detects patterns on the surface of the document; and an optical detector which determines the motion of the scanner as it is translated across the surface of the document, wherein the optical detector utilizes the method of any of claim 1 - 65 to determine the translation.
74. A scanner according to claim 73 wherein the patterns are printed patterns.
75. A scanner according to claim 73 wherein the patterns are handwritten patterns.
76. A scanner according to claim 75 wherein the patterns are a signature.
77. An encoder comprising: an optically diffusely reflecting surface; and an optical detector having relative motion with respect to the surface, wherein the optical detector measures relative motion with respect to the surface without utilizing markings on the surface.
78. An encoder comprising: an optically diffusely reflecting surface having no markings other than reference markings; and an optical detector having relative motion with respect to the surface, wherein the optical detector measures relative motion with respect to the surface relative to the reference markings.
79. An encoder according to claim 77 or claim 78 wherein the surface is the surface of a disk which rotates about an axis and wherein the detector measures the rotation of the disk.
80. An encoder according to any of claims 77-79 utilizing the method of any of claims 1-65.
81. A virtual pen comprising: an encoder according to claim 77; and circuitry which translates said measured relative motion into written or graphical data.
82. A virtual pen according to claim 81 utilizing the method of any of claims 1-65.
83. A device for moving a sheet of paper comprising: means for moving the paper; and an optical detector which measures the movement of the paper without utilizing any markings on the paper.
84. A device according to claim 83 wherein the optical detector utilizes the method of any of claims 1-65.
85. A document scanner comprising: a device according to claim 83 or claim 84; a reading head which reads information from the paper; and a memory which stores the information in memory locations responsive to the measurement of movement of the paper.
86. A printing machine comprising: a device according to claim 83 or claim 84; memory which contains information to be printed on the sheet of paper; and a printing head which prints the information responsive to the measurement of movement of the paper.
87. A facsimile machine comprising a scanner according to claim 85.
88. A facsimile machine comprising a printer according to claim 86.
89. A facsimile machine according to claim 88 and further comprising a scanner according to claim 85.
90. A method for determining the direction of relative motion of a surface with respect to a measurement device comprising: illuminating the surface with incident radiation such that radiation is reflected from portions of the surface toward a detector; placing an object, having an asymetric transmission function, adjacent to the detector; detecting the radiation reflected from the surface utilizing the detector to generate a signal; and determining the direction of relative motion of the surface from the signal.
PCT/IL1998/000113 1998-03-09 1998-03-09 Optical translation measurement WO1999046602A1 (en)

Priority Applications (26)

Application Number Priority Date Filing Date Title
AU66337/98A AU6633798A (en) 1998-03-09 1998-03-09 Optical translation measurement
PCT/IL1998/000113 WO1999046602A1 (en) 1998-03-09 1998-03-09 Optical translation measurement
US09/623,652 US6424407B1 (en) 1998-03-09 1998-03-09 Optical translation measurement
IL12430098A IL124300A0 (en) 1998-03-09 1998-05-03 Optical translation measurement
IL12543198A IL125431A0 (en) 1998-03-09 1998-07-20 Optical translation measurement
IL12665698A IL126656A0 (en) 1998-03-09 1998-10-19 Optical translation measurement
US09/264,410 US6330057B1 (en) 1998-03-09 1999-03-08 Optical translation measurement
US09/264,409 US6452683B1 (en) 1998-03-09 1999-03-08 Optical translation measurement
US09/264,411 US6246482B1 (en) 1998-03-09 1999-03-08 Optical translation measurement
CA002322874A CA2322874A1 (en) 1998-03-09 1999-03-09 Optical translation measurement
DE69904254T DE69904254T2 (en) 1998-03-09 1999-03-09 Optical translation measurement
JP54555899A JP3321468B2 (en) 1998-03-09 1999-03-09 Optical measurement of translation
IL13830499A IL138304A0 (en) 1998-03-09 1999-03-09 Optical translation measurement
CNB998002534A CN1144063C (en) 1998-03-09 1999-03-09 Optical translation measurement
EP99200686A EP0942286B1 (en) 1998-03-09 1999-03-09 Optical translation measurement
DE69900565T DE69900565T2 (en) 1998-03-09 1999-03-09 Optical translation measurement
EP99907827A EP1062519A2 (en) 1998-03-09 1999-03-09 Optical translation measurement
AU27439/99A AU750415B2 (en) 1998-03-09 1999-03-09 Optical translation measurement
EP99200687A EP0947833B1 (en) 1998-03-09 1999-03-09 Optical translation measurement
CNA2003101027889A CN1548963A (en) 1998-03-09 1999-03-09 Optical translational measurement
MXPA00009038A MXPA00009038A (en) 1998-03-09 1999-03-09 Optical translation measurement.
EP99200685A EP0942285B1 (en) 1998-03-09 1999-03-09 Optical translation measurement
PCT/IL1999/000137 WO1999046603A1 (en) 1998-03-09 1999-03-09 Optical translation measurement
NZ506914A NZ506914A (en) 1998-03-09 1999-03-09 Optical translation measurement
DE69900444T DE69900444T2 (en) 1998-03-09 1999-03-09 Optical translation measurement
US10/200,000 US6741335B2 (en) 1998-03-09 2002-07-19 Optical translation measurement

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Cited By (25)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6922248B2 (en) 2001-09-28 2005-07-26 Osram Gmbh Optoelectronic component for contactless measurement of movements between a measurement object and the optoelectronic component
EP2983070A1 (en) * 2008-12-05 2016-02-10 FlatFrog Laboratories AB A touch sensing apparatus and method of operating the same
EP1379833B1 (en) 2001-04-19 2016-06-01 Mapvision OY Method for indicating a point in a measurement space
US9651412B2 (en) 2011-01-31 2017-05-16 Sage Vision Inc. Bottle dispenser having a digital volume display
US9874978B2 (en) 2013-07-12 2018-01-23 Flatfrog Laboratories Ab Partial detect mode
US10019113B2 (en) 2013-04-11 2018-07-10 Flatfrog Laboratories Ab Tomographic processing for touch detection
US10126882B2 (en) 2014-01-16 2018-11-13 Flatfrog Laboratories Ab TIR-based optical touch systems of projection-type
US10146376B2 (en) 2014-01-16 2018-12-04 Flatfrog Laboratories Ab Light coupling in TIR-based optical touch systems
US10161886B2 (en) 2014-06-27 2018-12-25 Flatfrog Laboratories Ab Detection of surface contamination
US10168835B2 (en) 2012-05-23 2019-01-01 Flatfrog Laboratories Ab Spatial resolution in touch displays
US10176591B2 (en) 2012-06-15 2019-01-08 Sage Vision, Inc. Absolute position detection
US10282035B2 (en) 2016-12-07 2019-05-07 Flatfrog Laboratories Ab Touch device
US10318074B2 (en) 2015-01-30 2019-06-11 Flatfrog Laboratories Ab Touch-sensing OLED display with tilted emitters
US10401546B2 (en) 2015-03-02 2019-09-03 Flatfrog Laboratories Ab Optical component for light coupling
US10437389B2 (en) 2017-03-28 2019-10-08 Flatfrog Laboratories Ab Touch sensing apparatus and method for assembly
US10481737B2 (en) 2017-03-22 2019-11-19 Flatfrog Laboratories Ab Pen differentiation for touch display
US10496227B2 (en) 2015-02-09 2019-12-03 Flatfrog Laboratories Ab Optical touch system comprising means for projecting and detecting light beams above and inside a transmissive panel
US10761657B2 (en) 2016-11-24 2020-09-01 Flatfrog Laboratories Ab Automatic optimisation of touch signal
US11182023B2 (en) 2015-01-28 2021-11-23 Flatfrog Laboratories Ab Dynamic touch quarantine frames
US11256371B2 (en) 2017-09-01 2022-02-22 Flatfrog Laboratories Ab Optical component
US11301089B2 (en) 2015-12-09 2022-04-12 Flatfrog Laboratories Ab Stylus identification
US11474644B2 (en) 2017-02-06 2022-10-18 Flatfrog Laboratories Ab Optical coupling in touch-sensing systems
US11567610B2 (en) 2018-03-05 2023-01-31 Flatfrog Laboratories Ab Detection line broadening
US11893189B2 (en) 2020-02-10 2024-02-06 Flatfrog Laboratories Ab Touch-sensing apparatus
US11943563B2 (en) 2019-01-25 2024-03-26 FlatFrog Laboratories, AB Videoconferencing terminal and method of operating the same

Families Citing this family (147)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999046602A1 (en) * 1998-03-09 1999-09-16 Gou Lite Ltd. Optical translation measurement
US6329648B1 (en) * 1998-11-19 2001-12-11 Leroy C. Delatorre Phase locked loop fiber optic sensor system
AU5385699A (en) * 1999-08-26 2001-03-19 Otm Technologies Ltd. Edge detector
DE50014843D1 (en) * 1999-11-18 2008-01-24 Baumer Holding Ag Optical angle and / or distance measuring module
US6642506B1 (en) * 2000-06-01 2003-11-04 Mitutoyo Corporation Speckle-image-based optical position transducer having improved mounting and directional sensitivities
US6592039B1 (en) * 2000-08-23 2003-07-15 International Business Machines Corporation Digital pen using interferometry for relative and absolute pen position
ATE463004T1 (en) * 2000-11-06 2010-04-15 Koninkl Philips Electronics Nv METHOD FOR MEASURING THE MOTION OF AN INPUT DEVICE
KR100399637B1 (en) * 2000-12-21 2003-09-29 삼성전기주식회사 Optical mouse
KR100399635B1 (en) * 2000-12-21 2003-09-29 삼성전기주식회사 Optical mouse
GB0031612D0 (en) * 2000-12-27 2001-02-07 Koninkl Philips Electronics Nv Manually-operable input device
US7203383B2 (en) * 2001-02-22 2007-04-10 Thinkpen Llc Handwritten character recording and recognition device
US6599041B1 (en) * 2001-02-26 2003-07-29 Lexmark International, Inc. Sheet movement sensor
US6621483B2 (en) * 2001-03-16 2003-09-16 Agilent Technologies, Inc. Optical screen pointing device with inertial properties
US7065258B2 (en) * 2001-05-21 2006-06-20 Mitutoyo Corporation Systems and methods for reducing accumulated systematic errors in image correlation displacement sensing systems
EP1267301A1 (en) * 2001-06-13 2002-12-18 EM Microelectronic-Marin SA Device for detecting the movement of a surface of an object
EP1271395A1 (en) 2001-06-13 2003-01-02 EM Microelectronic-Marin SA Device for detecting the movement of a surface of an object
GB2377014B (en) * 2001-06-28 2005-08-03 Sendo Int Ltd Optical pointer device with switch
AUPR631801A0 (en) * 2001-07-12 2001-08-02 Luscombe, Andrew Roadside sensor system
EP1282018A1 (en) * 2001-08-03 2003-02-05 Nokia Corporation A wearable electronic device
DE20120335U1 (en) * 2001-12-17 2002-05-29 Behavior Tech Computer Corp Optical positioning device
JP2005526324A (en) * 2002-05-17 2005-09-02 コーニンクレッカ　フィリップス　エレクトロニクス　エヌ　ヴィ Device having an optical input device and at least one other optical device having a common radiation source
WO2003102751A2 (en) * 2002-06-04 2003-12-11 Koninklijke Philips Electronics N.V. Method of measuring the movement of an input device
TWI313835B (en) * 2002-06-04 2009-08-21 Koninkl Philips Electronics Nv Method of measuring the movement of an object relative to a user's input device and related input device,mobile phone apparatus, cordless phone apparatus, laptor computer, mouse and remote control
US8460103B2 (en) 2004-06-18 2013-06-11 Igt Gesture controlled casino gaming system
EP2241896B1 (en) 2002-09-23 2012-03-14 Stefan Reich Stabilising system for missiles
DE10258545B4 (en) * 2002-09-23 2008-01-24 Stefan Reich Method and system for stabilizing a translation motion size of a missile
KR100622404B1 (en) * 2002-10-23 2006-09-13 주식회사 애트랩 an optical image detector and optical mouse employing the same
EP1413974A1 (en) 2002-10-24 2004-04-28 Hewlett-Packard Company Hybrid sensing techniques for position determination
JP4745667B2 (en) * 2002-12-20 2011-08-10 アイタック システムズ，インコーポレイティド Cursor control device
US6729547B1 (en) 2002-12-30 2004-05-04 Motorola Inc. System and method for interaction between an electronic writing device and a wireless device
CN1244044C (en) * 2003-01-20 2006-03-01 张宏志 Mouse optical signal treatment method and device
US7110120B2 (en) * 2003-01-24 2006-09-19 Canon Kabushiki Kaisha Movement-direction determination apparatus
US7150716B2 (en) * 2003-02-20 2006-12-19 Siemens Medical Solutions Usa, Inc. Measuring transducer movement methods and systems for multi-dimensional ultrasound imaging
US7321359B2 (en) * 2003-07-30 2008-01-22 Avago Technologies Ecbu Ip (Singapore) Pte. Ltd. Method and device for optical navigation
US20040227954A1 (en) * 2003-05-16 2004-11-18 Tong Xie Interferometer based navigation device
US7303530B2 (en) * 2003-05-22 2007-12-04 Siemens Medical Solutions Usa, Inc. Transducer arrays with an integrated sensor and methods of use
ATE516529T1 (en) * 2003-06-02 2011-07-15 Koninkl Philips Electronics Nv OPTOELECTRONIC INPUT DEVICE AND METHOD FOR MEASURING THE MOTION OF AN OBJECT USING SUCH A DEVICE
US7227531B2 (en) * 2003-08-15 2007-06-05 Microsoft Corporation Data input device for tracking and detecting lift-off from a tracking surface by a reflected laser speckle pattern
US7161582B2 (en) * 2003-08-29 2007-01-09 Microsoft Corporation Data input device for tracking and detecting lift-off from a tracking surface by a reflected laser speckle pattern
US7110100B2 (en) * 2003-11-04 2006-09-19 Electronic Scripting Products, Inc. Apparatus and method for determining an inclination of an elongate object contacting a plane surface
US7444005B2 (en) * 2003-11-04 2008-10-28 Becton, Dickinson And Company Apparatus and method for using optical mouse engine to determine speed, direction, position of scanned device and to obtain quantitative or qualitative data from same
WO2005046443A2 (en) * 2003-11-07 2005-05-26 Georgia Tech Research Corporation Combination catheter devices, methods, and systems
NL1024895C2 (en) * 2003-11-27 2005-05-30 Enraf Nonius B V Device is for measurement of performed training movements on a training apparatus and is provided with a sensor for detection of movement when the apparatus is used
US7167162B2 (en) * 2003-12-12 2007-01-23 Avago Technologies Ecbu Ip (Singapore) Pte. Ltd. Apparatus and method for controlling a screen pointer
US7492351B2 (en) * 2003-12-18 2009-02-17 Avago Technologies Ecbu Ip (Singapore) Pte. Ltd. Optical navigation based on laser feedback or laser interferometry
US20050156915A1 (en) * 2004-01-16 2005-07-21 Fisher Edward N. Handwritten character recording and recognition device
EP1713399A4 (en) * 2004-02-06 2010-08-11 Georgia Tech Res Inst Cmut devices and fabrication methods
US7324575B2 (en) * 2004-02-17 2008-01-29 Finisar Corporation Lens with reflective surface
US7221356B2 (en) 2004-02-26 2007-05-22 Microsoft Corporation Data input device and method for detecting an off-surface condition by a laser speckle size characteristic
JP2007527285A (en) * 2004-02-27 2007-09-27 ジョージア テック リサーチ コーポレイション Multi-element electrode CMUT element and manufacturing method
JP2007531357A (en) * 2004-02-27 2007-11-01 ジョージア テック リサーチ コーポレイション Harmonic CMUT element and manufacturing method
US7646133B2 (en) * 2004-02-27 2010-01-12 Georgia Tech Research Corporation Asymmetric membrane cMUT devices and fabrication methods
US7023536B2 (en) * 2004-03-08 2006-04-04 Electronic Scripting Products, Inc. Apparatus and method for determining orientation parameters of an elongate object
US7242466B2 (en) * 2004-03-31 2007-07-10 Microsoft Corporation Remote pointing system, device, and methods for identifying absolute position and relative movement on an encoded surface by remote optical method
US7292232B2 (en) * 2004-04-30 2007-11-06 Microsoft Corporation Data input devices and methods for detecting movement of a tracking surface by a laser speckle pattern
US7369230B1 (en) 2004-04-30 2008-05-06 Donald Scott Rogers Apparatus and method for measuring particulate flow rate
US7285766B2 (en) * 2004-05-21 2007-10-23 Silicon Light Machines Corporation Optical positioning device having shaped illumination
US7773070B2 (en) 2004-05-21 2010-08-10 Cypress Semiconductor Corporation Optical positioning device using telecentric imaging
US20050259078A1 (en) * 2004-05-21 2005-11-24 Silicon Light Machines Corporation Optical positioning device with multi-row detector array
US7268341B2 (en) 2004-05-21 2007-09-11 Silicon Light Machines Corporation Optical position sensing device including interlaced groups of photosensitive elements
US20050259097A1 (en) * 2004-05-21 2005-11-24 Silicon Light Machines Corporation Optical positioning device using different combinations of interlaced photosensitive elements
US7042575B2 (en) * 2004-05-21 2006-05-09 Silicon Light Machines Corporation Speckle sizing and sensor dimensions in optical positioning device
US20050258346A1 (en) * 2004-05-21 2005-11-24 Silicon Light Machines Corporation Optical positioning device resistant to speckle fading
JP4479003B2 (en) * 2004-06-03 2010-06-09 株式会社セガ Image processing
US8684839B2 (en) 2004-06-18 2014-04-01 Igt Control of wager-based game using gesture recognition
DE102004035240A1 (en) 2004-07-21 2006-02-16 "Wolke" Inks & Printers Gmbh Identification device and labeling method
US20060023970A1 (en) * 2004-07-29 2006-02-02 Chinlee Wang Optical tracking sensor method
US7942744B2 (en) 2004-08-19 2011-05-17 Igt Virtual input system
US7126586B2 (en) * 2004-09-17 2006-10-24 Microsoft Corporation Data input devices and methods for detecting movement of a tracking surface by detecting laser doppler self-mixing effects of a frequency modulated laser light beam
US7528824B2 (en) * 2004-09-30 2009-05-05 Microsoft Corporation Keyboard or other input device using ranging for detection of control piece movement
US7138620B2 (en) 2004-10-29 2006-11-21 Silicon Light Machines Corporation Two-dimensional motion sensor
TWI252421B (en) * 2004-11-10 2006-04-01 Darfon Electronics Corp Optical pointing sensor and cursor control method thereof
US7248345B2 (en) * 2004-11-12 2007-07-24 Silicon Light Machines Corporation Signal processing method for use with an optical navigation system
WO2006068746A2 (en) * 2004-11-19 2006-06-29 Silicon Light Machines Corporation Dense multi-axis array for motion sensing
WO2006060798A2 (en) * 2004-12-02 2006-06-08 Silicon Light Machines Corporation Signal processing method for optical sensors
US8212775B2 (en) 2005-02-22 2012-07-03 Pixart Imaging Incorporation Computer input apparatus having a calibration circuit for regulating current to the light source
US8340476B2 (en) 2005-03-18 2012-12-25 The Invention Science Fund I, Llc Electronic acquisition of a hand formed expression and a context of the expression
US8229252B2 (en) 2005-03-18 2012-07-24 The Invention Science Fund I, Llc Electronic association of a user expression and a context of the expression
US7672512B2 (en) * 2005-03-18 2010-03-02 Searete Llc Forms for completion with an electronic writing device
US8232979B2 (en) 2005-05-25 2012-07-31 The Invention Science Fund I, Llc Performing an action with respect to hand-formed expression
US7873243B2 (en) 2005-03-18 2011-01-18 The Invention Science Fund I, Llc Decoding digital information included in a hand-formed expression
US8290313B2 (en) 2005-03-18 2012-10-16 The Invention Science Fund I, Llc Electronic acquisition of a hand formed expression and a context of the expression
US8102383B2 (en) 2005-03-18 2012-01-24 The Invention Science Fund I, Llc Performing an action with respect to a hand-formed expression
US8787706B2 (en) 2005-03-18 2014-07-22 The Invention Science Fund I, Llc Acquisition of a user expression and an environment of the expression
US20060213997A1 (en) * 2005-03-23 2006-09-28 Microsoft Corporation Method and apparatus for a cursor control device barcode reader
WO2006127142A2 (en) * 2005-03-30 2006-11-30 Worcester Polytechnic Institute Free-hand three-dimensional ultrasound diagnostic imaging with position and angle determination sensors
US20060238508A1 (en) * 2005-04-22 2006-10-26 Tong Xie Optical location measuring system
WO2006114764A2 (en) * 2005-04-27 2006-11-02 Koninklijke Philips Electronics N.V. Position measuring system
US7898524B2 (en) * 2005-06-30 2011-03-01 Logitech Europe S.A. Optical displacement detection over varied surfaces
US7557795B2 (en) * 2005-06-30 2009-07-07 Microsoft Corporation Input device using laser self-mixing velocimeter
US7399954B2 (en) * 2005-08-16 2008-07-15 Avago Technologies Ecbu Ip Pte Ltd System and method for an optical navigation device configured to generate navigation information through an optically transparent layer and to have skating functionality
US7543750B2 (en) * 2005-11-08 2009-06-09 Microsoft Corporation Laser velocimetric image scanning
US20070109267A1 (en) * 2005-11-14 2007-05-17 Microsoft Corporation Speckle-based two-dimensional motion tracking
US7505033B2 (en) 2005-11-14 2009-03-17 Microsoft Corporation Speckle-based two-dimensional motion tracking
JP4791811B2 (en) * 2005-12-06 2011-10-12 株式会社ミツトヨ Photoelectric rotary encoder
US7567235B2 (en) 2005-12-12 2009-07-28 Cypress Semiconductor Corporation Self-aligning optical sensor package
US7765251B2 (en) * 2005-12-16 2010-07-27 Cypress Semiconductor Corporation Signal averaging circuit and method for sample averaging
US8471191B2 (en) * 2005-12-16 2013-06-25 Cypress Semiconductor Corporation Optical navigation system having a filter-window to seal an enclosure thereof
TWI401460B (en) 2005-12-20 2013-07-11 Koninkl Philips Electronics Nv Device and method for measuring relative movement
US7737948B2 (en) * 2005-12-20 2010-06-15 Cypress Semiconductor Corporation Speckle navigation system
US7298460B2 (en) * 2006-01-03 2007-11-20 Silicon Light Machines Corporation Method for determining motion using a velocity predictor
US7884801B1 (en) 2006-02-16 2011-02-08 Cypress Semiconductor Corporation Circuit and method for determining motion with redundant comb-arrays
US7297912B1 (en) 2006-03-27 2007-11-20 Silicon Light Machines Corporation Circuit and method for reducing power consumption in an optical navigation system having redundant arrays
US7721609B2 (en) 2006-03-31 2010-05-25 Cypress Semiconductor Corporation Method and apparatus for sensing the force with which a button is pressed
US7809035B2 (en) * 2006-03-31 2010-10-05 Cypress Semiconductor Corporation Eye-safe laser navigation sensor
DE102006017753A1 (en) * 2006-04-11 2007-10-18 Visolux Zweigniederlassung Der Pepperl + Fuchs Gmbh Optical sensor for detecting relative movement of e.g. falling object, has receiver provided with switching circuit for optical navigation, where speed switching threshold per teach-in or potentiometer of switching output is adjustable
US7492445B1 (en) 2006-06-05 2009-02-17 Cypress Semiconductor Corporation Method and apparatus for robust velocity prediction
US7755604B2 (en) 2006-06-19 2010-07-13 Cypress Semiconductor Corporation Optical navigation sensor with tracking and lift detection for optically transparent contact surfaces
US7728816B2 (en) * 2006-07-10 2010-06-01 Cypress Semiconductor Corporation Optical navigation sensor with variable tracking resolution
DE102006041307A1 (en) * 2006-09-01 2008-03-13 Sick Ag Opto-electronic sensor arrangement
US7810972B2 (en) * 2006-10-13 2010-10-12 Visteon Global Technologies, Inc. Headlamp assembly having an adjustable light beam direction
US7742514B1 (en) 2006-10-31 2010-06-22 Cypress Semiconductor Corporation Laser navigation sensor
US8072429B2 (en) * 2006-12-22 2011-12-06 Cypress Semiconductor Corporation Multi-axial touch-sensor device with multi-touch resolution
TW200832191A (en) * 2007-01-19 2008-08-01 Leahsin Technologies Inc Method for controlling speckle size and distribution status and the optical system thereof
KR101484465B1 (en) * 2007-03-28 2015-01-28 아노토 아베 Optical component for a camera pen
DE102007023993B4 (en) 2007-05-23 2017-01-05 Continental Reifen Deutschland Gmbh Measuring device and method for determining path and / or angle coordinates and possible uses
US8314774B1 (en) 2007-07-09 2012-11-20 Cypress Semiconductor Corporation Method and apparatus for quasi-3D tracking using 2D optical motion sensors
US8263921B2 (en) 2007-08-06 2012-09-11 Cypress Semiconductor Corporation Processing methods for speckle-based motion sensing
US8187184B2 (en) * 2007-09-21 2012-05-29 Baxter International, Inc. Access disconnect system with optical and other sensors
US9011334B2 (en) * 2007-09-27 2015-04-21 Baxter International Inc. Access disconnect detection
US20090135140A1 (en) * 2007-11-27 2009-05-28 Logitech Europe S.A. System and method for accurate lift-detection of an input device
US8259069B1 (en) 2008-01-11 2012-09-04 Cypress Semiconductor Corporation Speckle-based optical navigation on curved tracking surface
US8031176B1 (en) 2008-01-22 2011-10-04 Cypress Semiconductor Corporation Optical navigation system using a single-package motion sensor
US7667855B2 (en) * 2008-02-29 2010-02-23 International Business Machines Corporation Providing position information to computing equipment installed in racks of a datacenter
US8416424B2 (en) * 2008-07-07 2013-04-09 Koninklijke Philips Electronics N.V. Laser self-mixing measuring device
US8541727B1 (en) 2008-09-30 2013-09-24 Cypress Semiconductor Corporation Signal monitoring and control system for an optical navigation sensor
US7723659B1 (en) 2008-10-10 2010-05-25 Cypress Semiconductor Corporation System and method for screening semiconductor lasers
US8217334B1 (en) 2008-12-24 2012-07-10 Cypress Semiconductor Corporation Optical navigation sensor including a spatial frequency filter
US8330721B2 (en) * 2009-02-19 2012-12-11 Avago Technologies Ecbu Ip (Singapore) Pte. Ltd. Optical navigation device with phase grating for beam steering
US8711096B1 (en) 2009-03-27 2014-04-29 Cypress Semiconductor Corporation Dual protocol input device
DE102010015014A1 (en) 2010-04-14 2011-10-20 Bayer Technology Services Gmbh Optical scanner
JP5668226B2 (en) * 2010-10-26 2015-02-12 株式会社ミツトヨ Photoelectric encoder
DE102010062959A1 (en) 2010-12-13 2012-06-14 Bayer Technology Services Gmbh position sensing
CN102959494B (en) 2011-06-16 2017-05-17 赛普拉斯半导体公司 An optical navigation module with capacitive sensor
US8896553B1 (en) 2011-11-30 2014-11-25 Cypress Semiconductor Corporation Hybrid sensor module
US8792526B2 (en) * 2012-05-24 2014-07-29 Northrop Grumman Systems Corporation Coherent laser array control system and method
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TWI543751B (en) * 2013-12-20 2016-08-01 緯創資通股份有限公司 Height measuring apparatus and method thereof
JP5832562B2 (en) * 2014-01-24 2015-12-16 ファナック株式会社 Reflective optical encoder with resin code plate
US9632657B2 (en) * 2014-12-28 2017-04-25 Sap Se Auxiliary input device
US9817488B2 (en) * 2015-01-21 2017-11-14 Pixart Imaging (Penang) Sdn. Bhd. Optical navigation device and related automatic magnification adjusting method
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WO2017025885A1 (en) * 2015-08-07 2017-02-16 King Abdullah University Of Science And Technology Doppler time-of-flight imaging
EP3420324B1 (en) * 2016-02-25 2021-03-24 Continuse Biometrics Ltd. A method and system for monitoring parameters of a moving object
CN105910631B (en) * 2016-04-07 2018-04-10 广东工业大学 Absolute grating scale and its measuring method
US10620447B2 (en) 2017-01-19 2020-04-14 Cognex Corporation System and method for reduced-speckle laser line generation
US10945706B2 (en) 2017-05-05 2021-03-16 Biim Ultrasound As Hand held ultrasound probe

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2636211B1 (en) * 1976-08-12 1977-06-02 Ibm Deutschland INTERFEROMETRIC PROCEDURE FOR DISTANCE OR FLATNESS MEASUREMENT
WO1988007208A1 (en) * 1987-03-18 1988-09-22 Deutsches Textilforschungszentrum Nord-West E.V. Process for measuring the speed and/or length of endless lengths of cloth, and device for implementing said process
US4794384A (en) * 1984-09-27 1988-12-27 Xerox Corporation Optical translator device
EP0479759A1 (en) * 1990-10-05 1992-04-08 RSF-Elektronik Gesellschaft m.b.H. Procedure and device for length or angle measurement
DE4219887C1 (en) * 1992-06-17 1993-11-18 Polytechnik Gmbh Input appts. for computer - has rotatable ball located in housing with segment extending over housing contour and sensor unit for rotating ball, and whose output signal acts as input signal
US5274361A (en) * 1991-08-15 1993-12-28 The United States Of America As Represented By The Secretary Of The Navy Laser optical mouse
EP0614086A1 (en) * 1993-03-05 1994-09-07 Canon Kabushiki Kaisha Velocity information detecting apparatus
JPH08285874A (en) * 1995-04-18 1996-11-01 Canon Inc Reference signal generator and rotational information detector employing the same
DE19615568A1 (en) * 1995-04-19 1996-11-14 Logitech Inc Pointing or indicating equipment with photodetector arrangement
WO1997043607A1 (en) * 1996-05-14 1997-11-20 Michel Sayag Method and apparatus for generating a control signal

Family Cites Families (30)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2772479A (en) 1955-06-14 1956-12-04 Fairchild Camera Instr Co Apparent-velocity responsive system
US3432237A (en) 1964-03-31 1969-03-11 Singer General Precision Velocity measuring device
US5159406A (en) 1964-09-28 1992-10-27 Zenith Electronics Corporation Light-operated accelerometer-type techniques
US3419330A (en) * 1965-04-06 1968-12-31 Sperry Rand Corp Diffraction grating angular rate sensor
US3511150A (en) 1966-01-13 1970-05-12 Theodore R Whitney Image motion devices
US3856403A (en) 1971-02-19 1974-12-24 Litton Systems Inc Velocity biased laser velocimeter
US3737233A (en) * 1971-02-22 1973-06-05 Singer Co Vector velocimeter
US3888589A (en) 1974-02-11 1975-06-10 Pilkington Perkin Elmer Ltd Reflection grating optical odometer
US4148585A (en) * 1977-02-11 1979-04-10 The United States Of America As Represented By The Department Of Health, Education & Welfare Three dimensional laser Doppler velocimeter
GB2043387B (en) 1978-12-27 1983-05-05 Marconi Co Ltd Optical velocity measurement
EP0095300B1 (en) 1982-05-25 1987-10-21 Plessey Overseas Limited Vehicle mounted doppler radar system
GB8511866D0 (en) 1985-05-10 1985-06-19 Pa Consulting Services Measuring instruments
JPS62172203A (en) * 1986-01-27 1987-07-29 Agency Of Ind Science & Technol Method for measuring relative displacement
GB8907101D0 (en) 1989-03-29 1989-05-10 Nat Res Dev Blood flow determination
GB2231221B (en) 1989-05-06 1993-06-16 Rolls Royce Plc A method of measuring the three dimensional velocity components of a particle in a fluid flow
US5274261A (en) 1990-07-31 1993-12-28 Texas Instruments Incorporated Integrated circuit degradation resistant structure
US5100230A (en) * 1990-10-12 1992-03-31 Hughes Aircraft Company True ground speed sensor
WO1992019930A1 (en) 1991-04-29 1992-11-12 Massachusetts Institute Of Technology Method and apparatus for optical imaging and measurement
US5243465A (en) 1992-05-12 1993-09-07 Tencor Instruments Area-division beamsplitter with broad spectral bandwidth
JPH06194116A (en) 1992-12-25 1994-07-15 Ntn Corp Laser length-measuring apparatus
US5829009A (en) 1993-01-07 1998-10-27 Texas Instruments Incorporated Method and device for storing and recalling information implementing a kanerva memory system
JP3144143B2 (en) * 1993-04-13 2001-03-12 ソニー・プレシジョン・テクノロジー株式会社 Optical displacement measuring device
DE59302118D1 (en) * 1993-05-21 1996-05-09 Heidenhain Gmbh Dr Johannes Photoelectric position measuring device
EP0634636B1 (en) 1993-07-07 1999-10-06 Deutsches Zentrum für Luft- und Raumfahrt e.V. Michelson-type interferometer
JPH07120554A (en) 1993-10-25 1995-05-12 Toyota Motor Corp Ground speed sensor
JP3279116B2 (en) 1994-03-22 2002-04-30 株式会社豊田中央研究所 Laser Doppler velocimeter
DE69512914T2 (en) 1994-07-08 2000-04-20 Risoe Forskningscenter OPTICAL MEASURING DEVICE AND METHOD
US5610705A (en) 1995-02-16 1997-03-11 Northrop Grumman Corporation Doppler velocimeter
DE19748802B4 (en) * 1996-11-20 2010-09-09 Dr. Johannes Heidenhain Gmbh Optical position measuring device
WO1999046602A1 (en) * 1998-03-09 1999-09-16 Gou Lite Ltd. Optical translation measurement

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2636211B1 (en) * 1976-08-12 1977-06-02 Ibm Deutschland INTERFEROMETRIC PROCEDURE FOR DISTANCE OR FLATNESS MEASUREMENT
US4794384A (en) * 1984-09-27 1988-12-27 Xerox Corporation Optical translator device
WO1988007208A1 (en) * 1987-03-18 1988-09-22 Deutsches Textilforschungszentrum Nord-West E.V. Process for measuring the speed and/or length of endless lengths of cloth, and device for implementing said process
EP0479759A1 (en) * 1990-10-05 1992-04-08 RSF-Elektronik Gesellschaft m.b.H. Procedure and device for length or angle measurement
US5274361A (en) * 1991-08-15 1993-12-28 The United States Of America As Represented By The Secretary Of The Navy Laser optical mouse
DE4219887C1 (en) * 1992-06-17 1993-11-18 Polytechnik Gmbh Input appts. for computer - has rotatable ball located in housing with segment extending over housing contour and sensor unit for rotating ball, and whose output signal acts as input signal
EP0614086A1 (en) * 1993-03-05 1994-09-07 Canon Kabushiki Kaisha Velocity information detecting apparatus
JPH08285874A (en) * 1995-04-18 1996-11-01 Canon Inc Reference signal generator and rotational information detector employing the same
DE19615568A1 (en) * 1995-04-19 1996-11-14 Logitech Inc Pointing or indicating equipment with photodetector arrangement
WO1997043607A1 (en) * 1996-05-14 1997-11-20 Michel Sayag Method and apparatus for generating a control signal

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 097, no. 003 31 March 1997 (1997-03-31) *

Cited By (42)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1379833B1 (en) 2001-04-19 2016-06-01 Mapvision OY Method for indicating a point in a measurement space
US6922248B2 (en) 2001-09-28 2005-07-26 Osram Gmbh Optoelectronic component for contactless measurement of movements between a measurement object and the optoelectronic component
EP2983070A1 (en) * 2008-12-05 2016-02-10 FlatFrog Laboratories AB A touch sensing apparatus and method of operating the same
US10048773B2 (en) 2008-12-05 2018-08-14 Flatfrog Laboratories Ab Touch sensing apparatus and method of operating the same
US10474249B2 (en) 2008-12-05 2019-11-12 Flatfrog Laboratories Ab Touch sensing apparatus and method of operating the same
US9651412B2 (en) 2011-01-31 2017-05-16 Sage Vision Inc. Bottle dispenser having a digital volume display
US10168835B2 (en) 2012-05-23 2019-01-01 Flatfrog Laboratories Ab Spatial resolution in touch displays
US10176591B2 (en) 2012-06-15 2019-01-08 Sage Vision, Inc. Absolute position detection
US11816856B2 (en) 2012-06-15 2023-11-14 Sage Vision Inc. Absolute position detection
US10019113B2 (en) 2013-04-11 2018-07-10 Flatfrog Laboratories Ab Tomographic processing for touch detection
US9874978B2 (en) 2013-07-12 2018-01-23 Flatfrog Laboratories Ab Partial detect mode
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US6330057B1 (en) 2001-12-11
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US6246482B1 (en) 2001-06-12
AU6633798A (en) 1999-09-27

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