WO1990013095A2

WO1990013095A2 - Equipment for capture of positional data

Info

Publication number: WO1990013095A2
Application number: PCT/GB1990/000654
Authority: WO
Inventors: Robert Horton; Roy Kevin Hills
Original assignee: Robert Horton; Roy Kevin Hills
Priority date: 1989-04-26
Filing date: 1990-04-26
Publication date: 1990-11-01
Also published as: WO1990013095A3

Abstract

Positional data, such as an outline of graphics on a page (1) is captured by following the outline with a stylus (4) to which are attached two inextensible lines (2a) each spooled at its other end within a housing (2) fixed in position in relation to the outline. As the stylus moves, the length of line unspooled or respooled is recorded and stored. This data can be converted into Cartesian coordinates for screen display. The housing typically contains step-up gearing to drive a slotted or apertured disc as the line respools or respools so that light pulses can be created and sensed through the rotating disc, and used as a digitised computer input for storage. More than two lines, and/or other non-physical links (RF, infrared, ultrasonic), and/or different measurement systems can be used.

Description

EQUIPMENT FOR CAPTURE OF POSITIONAL DATA

This invention relates to equipment for capture of positional data.

There are known devices for transferring, from a suitably prepared surface, positional data relating to e. g. a graphics display so that the data can be stored in a memory or displayed upon a suitable screen, at the time or at a desired later date. Typically, the data is captured by drawing or tracing the graphics upon a prepared surface equipped with a fine grid of parallel wires, so that movement of a stylus across the graphics, or touching the surface at separated points (depending upon the data capture program) will generate signals that can be stored for display or subsequent use.

These devices suffer from the drawback that they are rather elaborately constructed and accordingly rather expensive.

Other known devices utilize ultrasonic sound waves or a pantograph linkage.

There is thus a need for a device which enables graphics data from any surface to be transferred inexpensively into discs, tapes or computer memory.

There is a strong home computer market with an interest in graphics, and a large commercial market with graphics requirements of a fairly general type. For example, it is often required in business use to store some indication of shapes or graphical representations in some form of memory for later use, without however using the elaborate and expensive precision equipment available for computer-aided drafting.

The present invention sets out to provide inexpensive equipment which can capture positional data in a form suitable for such storage and of an acceptable degree of accuracy.

In one aspect the invention consists in equipment for capturing positional data comprising: a movable position-establishing member; a plurality of length-establishing means; a like plurality of length-measuring means associated one-to-one with the length-establishing means; a like plurality of immobilisation means associated one to one with the length-establishing means and each capable of defining a datum point in relation to said movable position-establishing member for capture of positional data by measured extension or retraction of the respective length-establishing means between the respective datum point and the position-establishing member as the said member is moved.

In a preferred aspect the invention consists in equipment for capturing positional data from a plane surface, comprising first length-establishing and length-measurement means; a second length-establishing and length-measurement means; a movable position- establishing member; and a first and second immobilisation means each capable of defining a datum point in relation to said movable position-establishing member, for capture of positional data by extension or retraction of the respective length-establishing means as the position-establishing member moves.

It will be apparent therefore that the positional data is captured not in Carterian coordinates, i. e. with reference to two axes at right angles, but by reference to the respective distances established between, and measured between, the position-establishing member on the one hand and each of the two datum points on the other.

Connection of the above equipment to the storage or computing system can be effected by a physical connector (e. g. a suitable cable) or by an infrared or like beam or by radio frequency transmission, especially for those embodiments described where the length-establishing means itself is not a physical linkage.

The length-establishing means can be a physical, elongate, flexible, inelastic, connector. Depending on scale this can be cable, wire, yarn or filament: an embodiment using inextensible polymer monofil, or metal - monofilament, is suitable for desk-top scale of operation.

Alternatively, the length-establishing means can be a light ray (visible, IR or laser) established in pulses between the stylus and each datum point, either location (or both locations) being the emitter. If required, a non-emitter location could reflect, so as to present a double or multiple path; but a more useful embodiment uses two receiver/transmitters, one triggering the other.

Similar systems can utilise radiofrequency waves or ultrasonics.

Where the length establishing means is physical, the length-measuring means can be part of the elongate connection itself, i. e. as a visible marking along the length or as a machine readable code of bars, dots or magnetic or other codings. More preferably, however, the length-measuring means is some form of pulse-emitting equipment driven in one direction or the other (as the length-establishing means varies in length, upon movement of the position-establishing member) and giving rise to a sequence of countable pulses in an ascertained direction. For example, and as described below, a filament can be spooled around an axis which drives by suitable step-up gears a slotted or perforate wheel permitting passage of pulses of light as a sensor. Alternatively, it can drive a tape, with calibrations or even absolute lengths marked magnetically upon it, past a suitable head.

Where the length-establishing means is a pulsed beam of laser or other light, or of infrared or like radiation, or of radio waves length-measurement means can comprise a beam timer to the degree of accuracy necessary for the scale of operation. Of course, a reflected beam (i. e. with transmitter and receiver in one unit) travels twice as far and distance can be measured twice as accurately. Multiple reflections increase accuracy still further. Systems can in practice involve transmitters and receivers at each end.

Preferably, and as discussed in more detail below the length-establishing means, whether physical or a light beam or I-R-beam, is located at the immobilisation or datum point. Thus, two elements of equipment each comprising a spool of monofilament (and a suitable pulse generation device) can be clamped to the upper edge of a drawing board and the monofilaments can meet at the stylus or other position-establishing member. Alternatively, I. R. emitters can be clamped in this way, for reflection at the position-establishing member.

However, it is also possible to locate the dispensing spools, or transmitter, at a puck unit including a stylus, and then merely fix the free ends of the filament (or establish fixed reflector locations, or receiver/transmitter locations) as the datum point in each case.

In one preferred form the invention consists in equipment for capturing positional data from a plane surface, comprising first spooling means biassed to wind an elongate flexible connector thereon, second spooling means also biassed to wind an elongate flexible connector thereon, and a stylus member to which the free end of each elongate flexible connector is attached; whereby if both spooling means are positionally immobilised each elongate connector can be pulled out over the plane to define the position of any point on that plane by derivation from the two unspooled or respooled lengths of connector.

Typically, the elongate connector is in each case a length of synthetic polymer monofilament. It may be spooled around a shaft biassed to wind up the filament and held within a housing further comprising means for generating a signal in relation to the length of filament or unspooled or respooled.

Two spaced housings, each dispensing a filament attached at the free end to a stylus point, will respool or unspool the filament to different extents as the stylus point is moved over a suitable graphics indication in the plane. The relative respooling and unspooling can be recorded, and is readily convertible to, for example, a depiction of the movement on screen in xy coordinates and/or to an assessment of the area enclosed within a loop movement.

It is conceivable that the filaments should actually touch and move across the surface. It is more preferable if they are slightly spaced from the surface, and if . they join the stylus accordingly at a region above its point. In such an instance it is usually important that the stylus be accurately at right angles to the surface, and one way of achieving this is to have the stylus held by a convenient block or "puck" or "mouse" for movement by hand across the plane. If desired, this block or "puck" can be provided with controls which have the effect of mode selection and of switching the information flow on or off.

However, as described in more detail below, the use of such a "puck", while convenient, is not essential. For example, a pen-like holder, or even a standard pen or pencil, could be used as the stylus, with suitable permanent or temporary attachment of monofilaments. A separate mode selector, positioned for example at the edge of the surface, could be present if desired. For many artistic purposes it is preferable to hold a pen or pencil-shaped artefact rather than manipulate a "puck", especially if it is desired to follow a contour and allow the drawing to be digitally reconstructed simultaneously.

Each housing containing a spool of filamentary material is preferably such that rotation of the spool axis is magnified by suitable gearing and caused to rotate, in a step up manner, a disc with regular apertures spaced around it to be capable of generating a sequence of light pulses as apertures successively register between a light source and light sensor means. In a known fashion, this system can also inform as to sense of movement of the disc. In another aspect the invention consists in the device as described above modified by containing at least one further such spool biassed to wind an elongate connecting member thereon, with the free end of the elongate connecting member also attached to the stylus; whereby if the three spools are positionally immobilised in a non-colinear manner positional data can be derived in terms of the three exposed lengths of connectoring member for conversion to x, y, z axes, or for depiction or volume calculation. Such three-dimensional systems could also use infra-red or like light beams, provided that care is taken to distinguish extranesus reflections.

The invention will be further described with reference to the accompanying drawings, in which: -

Figure 1 shows a typical general assembly of parts according to the invention for determining positional data relative to a graphics depiction,

Figure 2 shows diagrammaticall the attachment of the housing of one of the spool units of Figure 1,

Figures 3a, 3b and 3c show respectively a side view, end view and top view of a spool unit within each relevant external wall, and specfied internal components, removed for clarity of illustration,

Figure 4a and 4b show respectively a top view and side view of a puck unit as used in Figure 1,

Figure 5 shows a demountable stylus for the "puck" of Figures 4a and 4b,

Figure 6 shows diagrammatic lly a form of extension of the device shown in Figure 1 to capture positional data in three dimensions and

Figure 7 shows a variant of Figure 6.

Figure 8 shows a connector device for allowing to be connected monofilament to a standard pen or pencil.

The general assembly of parts shown in Figure 1 is assembled in relation to a drawingboard 1, although of course any plane support surface could be used. At the edge of the board are attached two identical spooling units 2, from which extend lengths of polymer monofilament 2a and 2b respectively. A readily manipulable control mouse 3 having a stylus point 4 is attached, at the stylus point, to the ends of the two lengths 2a, 2b of monofilament. The monofilaments 2a and 2b are biassed to respool inside of the spool units 2. Thus, wherever the puck 3 is moved they stay taut, and their respective lengths can be converted into x, y coordinates for the stylus. It is important to note that the spooling units can be placed an arbitrary distance apart, and that the drawingboard can be of different sizes. Provided that it is possible to mutually to define, for example, a top lefthand and a bottom righthand corner of a notional rectangular shape by suitable control at the puck unit 3, it will be possible to relate movements of that puck within the shape to a standardized set of' coordinates.

Each spooling unit 2 is in the form of a housing containing a number of windup and gear wheel elements. The housing 2 is preferably attached in such a way that the polymer monofilament 2a is spaced from the surface of the drawingboard 1. Figure 2, for example, shows an arrangement which the spooling unit 2 is mounted upon and edge clamp 5 which can be attached at 6 to a desired position on the drawingboard 1 so that the line is paid out at a small clearance above the surface.

The interior of each spooling unit 2 , as shown in Figures 3a, 3b and 3c comprises a windup drum and stepup gearing for the amounts moved by the unspooled or respooled filament. Each unit 2 comprises a vertical printed circuit board 7 and a horizontal partition wall 8. Above the horizontal partition wall 8 is a windup drum 9 on a shaft 9a. Within the drum, not shown, is a spiral spring such that the drum tends to turn in a direction to windup a filament upon its surface (see for example Figure 3, in which the bias is in the direction shown by the arrow on drum 9).

The filament passes from the windup drum 9, in several tight turns, about a friction pulley 10 mounted so as to be solid with shaft 10a. To ensure good contact between the filament and pulley 10 there is provided an opposing pulley 11, on shaft 11a, journalled at the end of an arm 12 which is biassed towards pulley 10 . Pulley 10 has a recessed drum, and opposed pulley 11 a corresponding enlargement to hold several turns of monofilament closely in contact with the drum.

Beneath the horizontal partition 8, and also solid upon shaft 10a, is a large peripherally toothed wheel 13. This meshes with small peripherally toothed wheel 14 on its shaft 14a, so that shaft 14a rotates much faster than shaft 10a.

Solid upon shaft 14a is an additional disc 15, with peripheral apertures or slots 16. As shaft 14a, rotates therefore, this disc 15 rotates at a relatively high speed and its periphery passes between component parts of optical sensor units 17. Two of these sensors 17 are shown in Figure 3c, but they have been omitted from other Figures for ease of illustration. Each unit 17 comprises an upper and lower portion, one generating a light signal and the other one having a sensor element for that signal. As the aperture 16 pass between the two portions of the optical sensor unit 17 they therefore create a train of pulses which represent in a ratio determined by the relative diameters of wheels 13, 14 and 15 the amount by which the filament 2a is unspooled or respooled.

The filament 2a comes out of the spooling unit between two vertical guide rollers 18, which are again have been omitted from Figures 3a and 3b for ease of illustration.

Figures 4a and 4b show details of the mouse construction. The puck 3 has peripheral ribbed gripping recesses 3a, whereby it can be readily held and slid over the plane surface. On its upper surface it is equipped with control buttons 19, 20 and 21, and an on/off indicator signal 22. At a flat forward face the puck carries forwardly extending mounting brackets 23. Rearwardly it is provided with electrical communication wiring at 24.

In use, the puck 3 mounts a stylus member 4, as shown in Figure 5. This consists of a synthetic polymer moulding, having a backplate 25, fixing lugs 25a which fit within the brackets 23 and a forwardly extending stem 26. At the front of the stem is a stylus mounting 27, having a waist portion 28 and terminating in stylus point 29. The filaments 2a and 2b are attached at the waist portion 28 of this stylus mounting. Making the stylus demountable in this fashion simplifies packaging and transport of the assembly.

The operation of the assembly shown above will be generally apparent from a study of the drawings. In use, the two spooling units 2 are attached to a suitable plane surface 1 at a convenient distance apart. Typically, a rectangular area of investigation is defined by recording the positions of diametrically opposite corners. Suitable arithmethical manipulation of the data will thereafter establish one corner as a datum point and the spaced therefrom by whatever scale is chosen. If desired, the device can be moved over a measured distance in the plane to record a true scale in the captured data. Thereafter, the device is moved as required within the plane. It may be moved so that the stylus 4 follows a given line, so that data is continuously recorded in a digitised fashion from such movement. It may alternatively be possible to operate such that the extent and position of given straight lines on the surface is recorded by suitable recordal of ends of the lines. In each case a digital representation of position is stored on a suitable medium for subsequent manipulation or display. If desired, the manipulation can include an assessment of area within a rectilinear or irregular shape.

The man skilled in the art will realise there are other possible modes of use. For example, although the two spools 2 are shown as extending along the same upper edge of the drawingboard, they could in theory be attached one to the upper and one to the lower edge of the board. In such an arrangement, care must be taken to define a field in which any given pair of lengths 2a and 2b are unique. This can be readily effected by defining two initial positions as corners of a reference rectangle. Then, even if unspooling members were placed halfway along the top and the bottom of the board respectively the two halves of the board (which would geometrically have mirror image positions for each pair of lengths 2a, 2b) could nonetheless be distinct in the store of data.

Although the invention is shown in relation to a drawingboard or like plane surface, the man in the art will realise that it can be used on a larger scale. Thus, the ^'invention could be embodied by having spooling ^■unit^'s" set a known (or arbitrary) distance apart upon a single staff which is vertically arranged in, say, the corner of a room and paid out to define shapes or areas (e. g. for repair or survey) on that wall. Other data recording uses in the general field of graphic art, draughtsmanship and surveying will be apparent to the man skilled in the art, provided that in each case they depend upon a digitised assessement of the length of two unspooled portions of elongate connector of some description.

If a third spooling means is provided, then, unless the three are arranged in a straight line, it is possible to assess a third dimension of measurement.

Figure 6 shows in simple form a possible embodiment for assessing, for example, the distances and undulations of an area 30. For example, such a measuring system could have uses in surveying, archeological research, etc. and in this instance comprises three unspooling units 2, each with their respective line 2a, 2b and 2c connecting to a stylus point 4 upon, for example, a pen-type holder 32. One of the unspooling units 2 is mounted upon a support 33 so as to be above the level of the other two, although the same effect could be achieved by mounting it behind the line of the other two. The data obtainable from the three unspooled lengths 2a, 2b and 2c gives a unique point for the stylus. 4, for example, upon the raised portion 31 of the sample plane 30.

A practical problem encountered with such an assembly is that the lines may encounter part of the relief and thus not give a true indication of the exact amount of spooling or respooling at the different spool units 2. This could be overcome as shown in Figure 7 by having the lengths 2a, 2b and 2c attached above the stylus point 4 of the holder 34. In such an instance it is important to have the holder completely vertical, although the software can compensate for spacing between the point of attachment of the lengths of filament and the actual stylus point itself. To ensure verticality it would be adequate to have some form of verticality-sensing switch within the stylus handle, in this way, a wider range of relief surfaces can be stored as numerical data for later calculation or display.

In Figure 8 a pencil or pen 81 is shown attached by rubber or like band 82 to a clip 83 openable at 83a to which, on the free vertical arm, are also attached at 84 the monofilaments 2a, 2b. This arrangement allows a conventional pen or pencil (81) to be used as a stylus, or while creating original graphics. The horizontal spacing (d) between the stylus point 81a and the attachment point 84 is generally unchanged, and the pencil or pen 81 is generally vertical, so that the graphics are stored are displayed to an acceptable degree of accuracy for general graphics work.

If desired, a constant term could be incorporated into the derivation of position point 81a, to conpensate for distance (d). More complex derivations, e. g. to allow for swivelling of the clip 83, can be utilised if desired within the scope of the invention as defined above.

An alternative embodiment of the invention utilises pulsed beams of light, especially I. R. light, and measures the time taken for beam travel.

The technique involves the relaying of an infrared signal pulse between the emitter and detector. The principle of operation allows the signal time lapse to be magnified, significantly reducing the circuit sensitivity required. In the standard configuration, the controlling circuitry would be housed in the sensing units and would consist of an infrared emitter, detector and sequencer. The puck would also contain an emitter and detector set at the same frequency.

In operation, the controlling circuitry would receive a request to initialise a length measurement. This would result in the start of the infrared relay sequence, transmitting the first infrared pulse to the stylus unit.

On receipt of this signal, the pulse would be retransmitted back to the sensor. The sequence would then be repeated a preset number of times, adding the transmission/detection times and detection- retransmission times to institute a total from which a single transmission-detection time can be calculated. The final total can then be used to calculate the distance between the sensor and the stylus unit.

By relaying the signal x number of times, the time from the initial transmission to the final detection is therefore multiplied by x. This therefore has the same effect as slowing the light beam down and makes the final length easier to calculate.

Claims

CLAIMS:

1. Equipment for capturing positional data comprising: a movable position-establishing member; a plurality of length-establishing means; a like plurality of length-measuring means associated one-to-one with the length-establishing means; a like plurality of immobilisation means associated one to one with the length-establishing means and each capable of defining a datum point in relation to said movable position-establishing member for capture of positional data by measured extension or retraction of the respective length-establishing means between the respective datum point and the position-establishing member as the said member is moved.

2. Equipment for capturing positional data from a plane surface, comprising first length-establishing and length-measurement means; a second length-establishing and length-measurement means; a movable position- establishing member; and a first and second immobilisation means each capable of defining a datum point in relation to said movable position-establishing member, for capture of positional data by extension or retraction of the respective length-establishing means as the position-establishing member moves.

3. Equipment as claimed in claim 1 or 2 in which the

*.*. length-establishing means is a physical elongate flexible inelastic connector.

4. Equipment as claimed in claim 3 in which the connector is made of polymer or metal monofilament.

5. Equipment as claimed in claim 3 or 4 in which the length-measuring means is located on the elongate connector.

6. Equipment as claimed in claim 3 or 4 in which the length-measuring means is a pulse-emitting means movable in one or other direction to give rise to a sequence of countable pulses as the length-establishment means varies in length.

7. Equipment as claimed in claim 6 in which the length-measuring means comprises a rotary axis about which the connector is spooled and suitable gearing from the axis to a rotary slotted or perforate wheel permitting pulses of light to pass to sensor means during rotation.

8. Equipment as claimed in claim 1 or 2 in which the length-establishing means is means for generating a light ray, radio frequency signal, or ultrasonic signal in pulses between the position-establishing member and each datum point.

9. Equipment as claimed in claim 8 in which a receiver-transmitter is located on the position establishing member and a second such receiver- transmitter is located at the datum point, so that each triggers the other for a repeated traverse of the distance between them.

10. Equipment as claimed in any one preceding claim in which each length-establishing means is located at the each respective datum point.

11. Equipment as claimed in any one preceding claim in which each length-establishing means is located on a movable unit also comprising the position-establishing means.

12. Equipment for capturing positional data from a plane surface, comprising first spooling means biassed to wind an elongate flexible connector thereon, second spooling means also biassed to wind an elongate flexible connector thereon, and a stylus member to which the free end of each elongate flexible connector is attached; whereby if both spooling means are positionally immobilised each elongate connector can be pulled out over the plane to define the position of any point on that plane by derivation from the two unspooled or respooled lengths of connector.

13. Equipment as claimed in claim 12 in which each elongate connector is a synthetic polymer monofil.

14. Equipment as claimed in claim 13 comprising a shaft about which each respective filament is spooled, biassing means acting on each shaft in a wind-up direction and means for generating a signal in relation to the length of filament unspooled or respooled.

15. Equipment as claimed in claim 14 in which each filament j oins the position-establishing means j ust above its point so that the filaments lie correspondingly j ust above the surface.

16. Equipment as claimed in claim 14 in which the position-establishing means comprises a puck holding a stylus.

17. Equipment as claimed in claim 14 in which the position-establishing means comprises a pen-like implement holding a stylus.

18. Equipment as claimed in claim 14 in which the said means for generating a signal comprises a rotary disc with regular apertures spaced around it and located between a light source and a light sensor, and gearing whereby the disc is rotatable to generate a series of pulses at said light sensor as the aperatures pass over the light source.

19. Equipment as claimed in claim 14, further comprising at least one further such spool biassed to wind an elongate connecting member thereon, with the free end of the elongate connecting member also attached to the stylus; whereby if the three spools are positionally immobilised in a non-colinear manner positional data can be derived in terms of the three exposed lengths of connectoring member for conversion to x, y, z axes, or for depiction or volume calculation.