WO1988000712A1

WO1988000712A1 - Optical scanner including position sensors

Info

Publication number: WO1988000712A1
Application number: PCT/US1987/001582
Authority: WO
Inventors: James R. Montgomery; John A. Figueroa; George White
Original assignee: Montgomery James R
Priority date: 1986-07-23
Filing date: 1987-07-02
Publication date: 1988-01-28
Also published as: JPH01500553A; EP0277964A4; AU593934B2; DE3785440D1; AU7753387A; EP0277964A1; JPH046150B2; US4797544A; EP0277964B1; DE3785440T2

Abstract

An optical scanning device (14) receives information from a page (11) of printed text (12) via an electrooptical transducer (16) and uses that information to fill a bit map in a memory device (102). In order to track the location of the optical scanner relative to the printed page, thus facilitating entry of information into the bit map, an optical mouse (19) is included in the scanner. In accordance with another embodiment of this invention, two optical mice (19, 150) are provided on the scanner (148) to indicate not only the position of the scanner relative to the page but also the angle that the scanner is held at relative to the page. The scanner can be used in conjunction with an optical character recognition device, a photocopying device, or any of a number of other devices. In accordance with another embodiment of this invention, indicia of location (210) are placed either on a transparent sheet or a mechanical constraint (200). A set of sensors (208) on an optical scanner (202) are adapted to sense this indicia but the sensors are spaced differently from the indicia, therefore indicating movement with very fine resolution.

Description

OPTICAL SCANNER INCLUDING POSITION SENSORS

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to optical scanners and more particularly to optical scanners using sensors for determining scanner position.

Description of the Prior Art

It is known in the art to use optical scanning devices in a variety of applications. For example, U.S. Patent No. 4,088,981 issued to Stephen Gott discusses a hand-held optical scanner used in conjunction with an optical character recognition unit (OCRU) which scans characters across a page as a means for entering data into a computer. U.S. Patent No. 4,240,748 issued to Blanc, et al. discusses another type of hand-held optical scanner used with an OCRU. These scanners typically include an array of photosensors which detect dark and light portions of a page and therefore the presence of printed characters. The photosensors are electrically coupled to an OCRU which identifies the printed characters and enters the characters into a device such as a computer memory.

In the prior art, determining the position of an optical scanner with respect to a page is a problem which has been dealt with in a number of ways. For example, U.S. Patent 3,238,501 issued to ak, et al., suggests a mechanism whereby an optical scanner is constrained to motion along a particular path. In this way, it is necessary to track position with respect to only one dimension. Other optical scanning devices require complicated software algorithms to determine the position of the scanner on the page. SUMMARY OF THE PRESENT INVENTION

An optical scanner constructed in accordance with the present invention is moved across a page containing printed text or other information. Between the scanner and the page is an transparency containing indicia of position. In one embodiment of the invention, the position indicia is printed across the transparency in a first color, while the information on the page is printed in a second color. In this way, a position sensor sensitive to the position indicia of the first color determines the position of the optical scanner relative to the page while a second sensor sensitive to the second color (or sensitive to black print) receives the desired information from the page.

In accordance with a second embodiment of the invention, the optical scanner includes two position sensors to provide information indicating not only the position of the scanner but also the angle at which the scanner is held relative to the printed text on the page.

In accordance with another embodiment of the invention, a constraint confines the optical scanner to motion along a first axis across the page. The constraint includes a plurality of lines evenly spaced along the path of the optical scanner which serves as position indicia. The optical scanner includes an array of photosensing elements, spaced slightly differently from the plurality of lines. Because of this difference in spacing, the position of the scanner is determined with resolution that is finer than the spacing of the plurality of lines. These and other features of the invention are better understood with reference to the drawings below.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is an illustration of a page of text covered by a transparency across which an optical scanning device moves. Figure 2 is an illustration of the bottom of the optical scanning device of Figure 1.

Figure 3 is a block diagram of the optical scanning device of Figure 1 connected to an OCRU. Figure 4 is a block diagram of a second circuit used with the optical scanning device of Figure 1.

Figures 5a and 5b are illustrations of optical scanning devices being held at first and second angles, respectively, relative to text on a page. Figure 6 is an illustration of the bottom of an optical scanning device with two position sensing devices.

Figure 7 is a block diagram of a circuit which processes electrical signals from the scanner of Figure 6. Figure 8a is an illustration of an optical scanner and a constraint for confining the scanner to motion along a given direction.

Figure 8b is an illustration of the scanner of Figure 8a.

Figure 8c is a prospective view of the constraint of Figure 8a.

Figures 9a and 9b illustrate a set of lines spaced at a first distance and a set of sensors spaced at a second distance, thereby enabling detection of motion with enhanced resolution. Figures 10 and 11 illustrate an optical scanner constructed in accordance with another embodiment of the invention.

Figure 12 is an illustration of an optical scanner affixed to a pair of movable arms which keep the scanner at a specific angle relative to a surface.

BRIEF DESCRIPTION

An optical scanner constructed in accordance with the present invention includes a plurality of photosensitive elements for receiving an image, e.g., text or a pictu e formed on a surface. The scanner also includes a sensor which monitors the position of the scanner relative to the surface. In this way, a device receiving signals from the scanner (e.g., a computer, OCRU, etc.) receives signals indicative of both the image formed on the surface and where on the surface that image is located.

In one embodiment of the invention, two sensors monitor the position of the scanner and provide information indicating the angle at which the scanner is held. In other embodiments, the scanner is constrained to a particular angle relative to the image by a mechanical constraint.

Referring to Figure 1, a book 10 includes a page 11 with printed text 12 thereon. It is desirable to be able to enter text 12 from book 10 into an electronic device such as a computer without having to. type the text on a keyboard. Therefore, an optical scanning device 14 constructed in accordance with one embodiment of the present invention is provided which includes a photoelectric sensor 16 (Figure 2). Photoelectric sensor 16 scans text 12 and provides electrical output signals in response thereto. Photoelec¬ tric sensor 16 can be any of a number of devices. In one embodiment of the invention, photoelectric sensor 16 is a device such as model number TC103-1, which is a CCD array available from Texas Instruments. In an alternative embodiment of the invention, a dynamic RAM is used to sense light from page 11 as discussed in U.S. Patent 4,344,091 issued to Gardener, et al., which is incorporated herein by reference. (Gardener discusses a dynamic RAM used as a photoelectric sensor. Light is permitted to strike the cells of the dynamic RAM, thus selectively changing the state of cells in the dynamic RAM in response to the position of those cells relative to printed text). Other types of photosensing devices can be used as well.

It is also desirable to have information corresponding to the position of optical scanning device 14 relative to page 11. Accordingly, a transparency 18 is provided between optical scanning device 14 and page 11. Transparency 18 has printed thereon indicia indicative of position which is sensed by an optical mouse mechanism 19. In one embodiment of the invention, optical mouse mechanism 19 is of the type discussed in U.S. Patent 4,364,035, issued to Steven T. Kirsch on December 14, 1982 and incorporated herein by reference. In such a mechanism, transparency 18 has a set of evenly spaced horizontal lines of a first color, e.g., red, and a set of evenly spaced vertical lines of a second color, e.g., green. A sensor within mouse mechanism 19 senses when optical scanner 14 moves across the green and red lines. The number of lines crossed during a scanning operation is then added to determine the position of optical scanner 14 with respect to transparency 18. A light source 21 provided on the bottom of optical scanning device 14 alternately provides red and green light to enable mechanism 19 to separately detect the red and green lines. (In an alternative embodiment, page 11 includes the horizontal and vertical lines as well as text 12, thus obviating the need for transparency 18.)

Referring to Figure 3, photoelectric sensor 16 senses text 12 on page 11 and generates electrical signals in response thereto, which are communicated to an optical character recognition unit (OCRU) 22. In addition, OCRU 22 also receives signals from optical mouse mechanism 19 indicative of the position of scanning device 14. OCRU 22 performs any of a number of optical character recognition algorithms to identify characters being scanned. In one embodiment, as OCRU 22 receives signals indicative of the presence of print at a particular point on page 11 as well as information indicating the position of that point, OCRU 22 uses this information to construct a bit map in a memory device 23. (The bit map is an array of data bits, each corresponding to an area of page 12. If text is printed on an area corresponding to a given data bit, that data bit assumes a state indicative of the presence of printed text. Otherwise, the given data bit assumes the opposite state.) OCRU 22 then uses either a template matching algorithm, e.g., as described in U.S. Patent 3,165,718, issued to Harold Fleisher (incorporated herein by reference), or a feature extraction algorithm, e.g., as described in U.S. Patent 4,193,056, issued to Morita, et al., (incorporated herein by reference) to identify the character scanned, and presents data corresponding to the identified character to a computer 24. In one embodiment of the invention, computer 24 is an IBM personal computer, although other computers are also appropriate.

Figure 4 is a block diagram of another embodiment of the invention using optical scanning device 14 to fill in a bit map array within a memory device 102. In this embodiment, the circuit illustrated merely fills -in the bit map array and does not necessarily perform any optical character recognition. In Figure 4, photoelectric sensor 16 is a CCD device which includes an array of roughly 2,000 photosensitive cells arranged along a one inch line segment. CCD device 16 provides an analog output signal on a line 104, serially indicating the amount of light received by each photosensitive cell within CCD device 16. The analog signal on line 104 is presented to a circuit 106 which removes an offset voltage inherent in the output signal on line 104. Circuit 106 then provides an output signal on a line 108 which is received by an analog to digital converter 110. Analog to digital converter 110 provides an 8 bit digital output signal on an 8 bit bus 112 indicative of the amplitude of the signal received on line 108 which in turn is indicative of the amount of light which strikes the photosensitive cells within CCD device 16. The data on bus 112 is then presented to a host computer 100 in one of two modes. In a first mode, if scanner 14 is being used to scan text printed in black and white, then the most significant bit of bus 112, which indicates whether a photosensitive cell scanned a white portion of the page or a black portion of the page, is 5 presented to a shift register 114. Shift register 114 accumulates 8 bits of data corresponding to the most significant bit generated in response to light received by eight photosensitive cells within CCD device 16 and presents those 8 bits to a multiplexer llδ. The output signals from ° multiplexer 116 are stored in a latch 118 which is coupled to an interface circuit 120 which in turn is coupled to computer 100. Computer 100 accumulates data from latch 118 in the bit map array within memory 102 and dumps the information stored therein to a high resolution monitor such as a CRT 122.

In a second mode of operation, multiplexer 116 provides the seven least significant bits of data on bus 112 and presents that data to computer 100 via latch 118 and interface circuit 120. In addition, shift register 114 accumulates the most significant bits of data from bus 112, and multiplexer 116 periodically transmits the output signals from shift register 114 to latch 118. In this way, information corresponding to the scanned image includes information indicative of the relative intensity of light received by each of the photosensitive elements within CCD device 16. An image is provided to CRT 122 which indicates the relative intensity of the various shades of gray received by the photosensitive elements within CCD device 16. Also illustrated in Figure 4 is a timing generator 124 which provides clock signals to CCD device 16. As is well known in the art, CCDs are analog shift registers and therefore require a series of clock pulses to shift the information out of the CCD and into buffer 106. Timing generator 124 is also coupled to shift register 114 and analog to digital converter 110 to synchronize operation of these devices with the shifting of data out of CCD device 16. Timing generator 124 also receives output signals from mouse 19. Every time mouse 19 encounters an indicia of position, e.g., one of the vertical or horizontal lines formed on transparency 18 (Figure 1), mouse 19 provides an output signal to timing generator 124 which in turn causes CCD device 16 to provide output signals indicative of the state of each photosensitive cell in the CCD on line 104. Also illustrated in Figure 4 is an exposure time and mode selection latch 126 which controls the exposure sequence for the cells in CCD device 16 as well as the mode of operation as previously discussed. In addition, a DMA handshake circuit 128 is provided which controls the flow of information between latch 118 and interface circuit 120.

In another embodiment of the invention, computer 100 is a microprocessor chip. Computer 100 stores data provided by scanner 14 in memory 102. Computer 100 is then subsequently coupled to a dot matrix printer 129 which provides a hard copy of the page scanned by scanner 14. In this way, for example, a person using a library can copy pages from a book by scanning those pages. The information scanned is stored in memory 102, and is later dumped onto paper by printer 129 at a convenient time. In this way a user need not carry books to a photocopy machine when it is desired to copy a page. Depending on the size of memory 102 and the resolution of printer 129, photographs as well as text can be copied by scanner 14.

Because optical scanning device 14 is a hand held device, it is possible to tilt optical scanning device 14 at an angle relative to text 12 while scanning the information on page 11. If that happens, a slightly inaccurate bit map is stored by computer 100 in memory 102. For example, if the optical scanning device 14 is held at a first angle, CCD device 16 will be oriented vertically as illustrated in Figure 5a and the information provided by a photosensitive cell at the top of CCD device 16 will sense the presence of text at a position different from the position sensed if optical scanning device 14 was held at a different angle, e.g., as illustrated in Figure 5b. Because of this, in accordance with a second embodiment of the invention, a scanning device 148 includes a second mouse 150 and a second light source 151 (Figure 6) to provide the host computer with information indicative of the orientation of scanning device 148. Referring to Figure 6, mouse 19 and mouse 150 provide electrical pulses indicative of their travel across transparency 18. In this way, the host computer tracks the position of mouse 19 and 150, and therefore the angle that scanner 14 is held at. In this way, as CCD device 16 provides a signal indicative of the light received from a given photosensitive cell, computer 100 more accurately calculates which bit map position that signal corresponds to.

Figure 7 is a block diagram of a circuit used to monitor the position of mouse 19 and mouse 150. As can be seen in Figure 7, mouse 19 provides a series of pulses on a line XI indicative of mouse 19 crossing one of the vertical lines on transparency 18. Similarly, mouse 19 also provides pulses on a line Yl indicative of mouse 19 crossing one of the horizontal lines on transparency 18. Mouse 150 provides similar pulses on a line X2 and a line Y2. These pulses are received by a set of four up down counters 152 which determine the position of mice 19 and 150 in response thereto and communicate the X and Y position of each mouse on buses XP1, XP2, YP1 and YP2. Every time a "mouse event" occurs (i.e., one of mice 19 or 150 crosses a horizontal or vertical line) CCD device 16 provides a series of output signals on a line 154 which is received by a digitizer 158 which in turn provides a series of digital output pulses on a line 160. As each pulse (indicative of the information received by an associated photosensitive cell within CCD device 16) is provided on line 160, a map calculation circuit 162 calculates the position (i.e., X and Y coordinates) of that photosensitive cell, calculates the pixel address corresponding to that position, and provides that address to a memory 166. (A pixel is a bit or word within a bit map array.) The contents of memory 166 are then read by a host computer 168.

In another embodiment, instead of providing signals on a single line 160, digitizer 158 provides data on a bus of several lines in order to indicate various shades of gray sensed by the sensing elements of CCD device 16.

It is noted that it is possible that not all the pixels in memory 166 may be filled after scanner 148 scans a portion of page 11. Accordingly, in one embodiment, computer 168 fills in empty pixels by averaging the values stored in memory 166 corresponding to the surrounding pixels.

Referring to Figure 8a, another embodiment of the invention includes a constraint 200 along which an optical scanner 202 moves. Constraint 200 is affixed to a set of supports 201a, 201b, which can be adjusted to enable constraint 200 to slide in a direction indicated by arrow A relative to supports 201a, 201b. Supports 201a, 201b are affixed to transparency 204 which is placed on page 11. Constraint 200 includes indicia of position 210 (Figures 8c) . Optical scanning device 202 includes a plurality of sensors 208 along one edge (Figure 8b) for sensing indicia 210. As optical scanning device 202 moves along constraint 200 in a direction indicated by Arrow B, sensors 208 receive information corresponding to the position of scanning device 202 and provide that information to a computer or OCRU as described above along with the information scanned on page 11.- (In another embodiment, indicia 210 are formed on supports 201a, 201b, and scanner 202 slides along supports 201a or 201b in the direction of arrow A. Constraint 200 keeps scanner 202 vertically oriented.)

In one embodiment of the invention, indicia 210 are a set of parallel lines evenly spaced along constraint 200. Plurality of sensors 208 are spaced slightly differently than lines 210. Because of this, a pattern is created which enhances the resolution achieved by sensors 208. This can best be understood with reference to Figure 9a and 9b.

Referring to Figure 9a, lines 210 are indicated by the lower set of boxes while sensors 208 are indicated by the upper set of boxes. Lines 210 are provided such that the distance between the center of adjacent lines is 1 distance unit, and the distance between the center of adjacent sensors 208 is less' than 1 unit, e.g., 15/16 units. When a sensor, e.g., sensor 208a is aligned with line 210a, it receives a minimum amount of light, indicated by black square 209. When a sensor such as sensor 208b is completely misaligned from any of lines 210, it receives a maximum of light. Referring to Figure 9b, if scanner 202 is moved roughly 3/16 units with respect to lines 2.10, instead of sensor 208a receiving a minimum amount of light, a sensor 208c receives a minimum amount of light. Thus, even though lines 210 are spaced one every distance unit and sensors 208 are spaced one every 15/16 distance units, sensors 208 can be used to detect movement with a much smaller resolution, in the case of Figure 9b, 3/16 distance units. Thus, in accordance with one embodiment of the invention, indicia 210 are spaced differently from sensors 208 to enhance resolution of motion. A similar technique can be employed with the indicia on transparency 18 in the previously discussed embodiments. In such an embodiment, instead of using a single mouse 19 (Figure 2), a plurality of sensors is provided spaced along horizontal and vertical axes and spaced differently from the horizontal and vertical lines on transparency 18 in order to detect motion of scanner 14 with high resolution.

Referring to Figure 10, another embodiment of this invention uses a lense 250 to focus an image of, page 11 on a 5 screen 252. An optical scanner 254 detects the image on screen 252 and provides data indicative of that image to a host computer (not shown). Figure 11 illustrates the side of scanner 254 facing screen 252. Scanner 254 includes a linear CCD array 256 which is moved in a direction indicated

10 by arrow D (Figure 10) relative to screen 252. A set of regularly spaced lines 260 are placed on one side of screen 252. A set of position sensors 262 on scanner 254 senses the motion of scanner 254 relative to screen 252. In this * way, accurate information indicative of the position of

-*-5 scanner 254 relative to screen 252 is provided to the.host computer. In one embodiment, lines 260 are spaced at intervals different from the spacing of sensors 262. In ^• this way, enhanced resolution is achieved in the same manner as the resolution achieved with the above-described lines

20 210 and sensors 208. In one embodiment of this invention, after an image is focused on screen 252, scanner 254 is moved in the directions indicated by arrow D by an electro¬ mechanical device such as a motor (not shown) controlled by the host computer.

25 In accordance with another embodiment of this invention, an optical scanner 300 (Figure 12) is affixed to a first movable arm 302 which is affixed to a second movable arm 304. Movable arms 302 and 304 are designed so that optical scanner 300 always remain at the same angle relative

30 to a surface 306 as it moves across surface 306. This is done using mechanical apparatus that is common in conven¬ tional drafting tables. On surface 306 is a transparency 308 which includes indicia of position. In this way, scanner 300 can be used in conjunction with a conventional

35 drafting table to receive information on page 11 on surface 306.

In alternative embodiments of the invention, instead of using a mouse having electrooptical sensors, other types of mice, such as an electromechanical mouse can be used. Electromechanical mice typically include an upside down trackball which contacts a surface. As the mouse moves across the surface, the trackball rotates. This rotation is sensed, e.g., using the apparatus discussed in U.S. Patent 4,496,936, issued to Dan Kramer, incorporated herein by reference.

While the invention has been taught with reference to specific embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention. Accordingly, all such changes come within the scope of the present invention.

Claims

CLAIMSWe claim:

1. An image scanner comprising: means for scanning information on a surface; and means for providing information indicative of the position of said scanner relative to said surface.

2. The image scanner of Claim 1 wherein said means for scanning comprises at least one photosensitive element for scanning information on said surface.

3. The image scanner of Claim 1 wherein said image scanner comprises an array of photosensitive elements for scanning information on said surface.

4. The image scanner of Claim 3 wherein said array of photosensitive elements is a CCD device.

5. The image scanner of Claim 3 wherein said array of photosensitive elements comprises a dynamic RAM.

6. The image scanner of Claim 1 wherein said means for providing is an electromechanical mouse.

7. The image scanner of Claim 1 wherein said means for providing is a mouse which determines the position of said image scanner in response to light.

8. Apparatus for scanning a surface containing information comprising: an image scanner having an array of photosensitive elements, said photosensitive elements being adapted to scan information on said surface; and a transparency, including indicia of position, said transparency being adapted to cover at least a portion of said surface, said image scanner being adapted to be moved across said transparency, said image scanner including a mouse adapted to sense said indicia and provide electrical signals in response thereto.

9. The apparatus of Claim 8 wherein said transparency includes a first set of parallel lines of a first color and a second set of parallel lines of a second color, said second set of parallel lines being orthogonal to said first set of parallel lines, and wherein said mouse senses the passage of said scanner over said first and second sets of parallel lines.

10. An image scanner comprising: means for scanning information on a surface; first means for providing information indicative of the position of said first means relative to said surface; and second means for providing information indicative of the position of said second means relative to said surface, wherein the position of said first means and said second means is used to calculate the position of said means for scanning relative to said surface.

11. The image scanner of Claim 10 wherein said means for scanning is an array of photosensitive elements, and wherein information from said array of photosensitive elements is provided to a memory device, said memory device having a plurality of locations, each location corresponding to a position in a bit map.

12. The image scanner of Claim 11 wherein said memory device is coupled to a printer, said printer providing a hard copy of the information stored in said memory device.

13. Image scanning apparatus comprising: an optical scanner having at least one photosensi¬ tive element, said photosensitive element being adapted to scan information on a page; a constraint for limiting motion of said optical scanner to motion along a first direction, said optical scanner further comprising means for determining the position of said optical scanner relative to said page.

14. The image scanning apparatus of Claim 13 wherein said image scanner moves along said constraint, said constraint having indicia of position formed thereon, said means for determining detecting said indicia.

15. The image scanning apparatus of Claim 14 wherein said indicia comprise a set of marks spaced at a first distance, said means for determining comprising a plurality of sensors spaced at a second distance not equal to said first distance, said sensors detecting changes in position of said optical scanner of less than said first or second distance.

16. Optical scanning apparatus comprising: an image scanner having at least one photosensi- tive element, said photosensitive element being adapted to scan information printed in a first color on a page; and a transparency including indicia of a second color indicative of position, said transparency being adopted to cover said page, said image scanner being adapted to be moved across said transparency, said image scanner including means for sensing passage of said image scanner over said indicia of said second color.

17. The optical scanning apparatus of Claim 16 wherein said indicia comprises a set of marks evenly spaced at a first distance, said means for sensing comprising a set of sensors evenly spaced at a second distance not equal to said first distance so that enhanced resolution of motion is detected by said sensors.

18. Optical scanning apparatus comprising: a screen having indicia of position on a portion thereof; means for focusing an image on said screen; an optical scanner having at least one photosensi¬ tive element being adapted to scan said image, said optical scanner also including means for sensing said indicia of position.

19. The optical scanning apparatus of Claim 18 wherein said indicia are a set of evenly spaced marks and said means for focusing comprises a lense.

20. The image scanner of Claim 1 wherein said means for scanning comprises at least one photosensitive element for scanning information on said surface, and wherein a constraint is provided for limiting motion of said image scanner to motion along a first direction.

21. The image scanner of Claim 20 wherein said constraint includes indicia of position formed thereon, said means for providing sensing said indicia of position.

22. The image scanner of Claim 1 wherein said means for scanning information comprises at least one photo- sensitive element, said photosensitive element for scanning informaton printed in a first color on said surface, and wherein a transparency including indicia of a second color indicative of position covers said surface, said image scanner being adapted to be moved across said transparency, and wherein said means for providing senses passage of said image scanner over said indicia of said second color.

23. The image scanner of Claim 1 wherein said surface comprises a screen having indicia of position on a portion thereof, and wherein means are provided for focusing an image on said screen, said means for scanning information having at least one photosensitive element for scanning said image, said means for providing information including means for sensing said indicia of position..

24. Apparatus comprising: a surface having information recorded thereon; and a scanning device including means for scanning said information, and means for providing information indicative of the position of said scanner relative to said surface.