GB1575420A - Position resolving apparatus - Google Patents

Position resolving apparatus Download PDF

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Publication number
GB1575420A
GB1575420A GB982577A GB982577A GB1575420A GB 1575420 A GB1575420 A GB 1575420A GB 982577 A GB982577 A GB 982577A GB 982577 A GB982577 A GB 982577A GB 1575420 A GB1575420 A GB 1575420A
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United Kingdom
Prior art keywords
apparatus
beam
light
display area
retro
Prior art date
Legal status (The legal status 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 status listed.)
Expired
Application number
GB982577A
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BAE Systems Electronics Ltd
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BAE Systems Electronics 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 BAE Systems Electronics Ltd filed Critical BAE Systems Electronics Ltd
Priority to GB982577A priority Critical patent/GB1575420A/en
Publication of GB1575420A publication Critical patent/GB1575420A/en
Application status is Expired legal-status Critical

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Classifications

    • GPHYSICS
    • G06COMPUTING; CALCULATING; COUNTING
    • G06FELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00Input 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
    • G06F3/01Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/042Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by opto-electronic means
    • G06F3/0421Digitisers, 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
    • G06F3/0423Digitisers, 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 using sweeping light beams, e.g. using rotating or vibrating mirror
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO 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
    • G01S5/00Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/16Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using electromagnetic waves other than radio waves

Description

(54) IMPROVEMENTS IN OR RELATING TO POSITION RESOLVING APPARATUS (71) We, THE MARCONI COMPANY LIMITED, a British Company, of Marconi House, New Street, Chelmsford, Essex CMi 1PL do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to position resolving apparatus and in particular to position resolving apparatus for providing indications of the location of a position, of interest on a display such as the display of a television display apparatus.

Such position resolving apparatus find wide application for such purposes as surveillance and a number of types of position resolving apparatus are at present known.

One form of known position resolving apparatus is based upon the C. A. D. (computer aided design) light pen, which is capable of producing an X Y co-ordinate output, which in most cases is desired, but which does not operate entirely satisfactorily where low contast targets are in question.

Other forms of position resolving apparatus involve the use of a wire grid overlay which is placed upon the display and pressure is applied to the wire grid intersections adjacent positions of interest. One serious disadvantage with such position resolving apparatus is that the wire grid itself tends to obscure the display and the greater the resolution which is obtained (or in other words the finer the grid), the more the display is obscured.

Another known form of position resolving apparatus makes use of an electronically scanned light emitting diode photo transistor grid arrangement which detects the position of a finger or other probe interrupting the light paths extending across the display between the light emitting diodes and the photo transistors. Such position resolving apparatus tend to be expensive and become the more expensive the greater the resolution which is provided.

The present invention seeks to provide an improved position resolving apparatus in which one or more of the above difficulties are reduced.

According to this invention a position resolving apparatus comprises means for sweeping two light beams across a common display area, a retro-reflective reflector arrangement arranged to surround at least part of the boundary of said display area and in the paths of said beams after they have crossed said display area and means responsive to light reflected back along the path of each beam for detecting when, in time relation with its sweep, each beam is obstructed by a probe placed at a position of interest in said display area to provide positional information relating to the position of said probe.

Said probe may be a point or a human finger.

Preferably said light beams are visible light beams.

Preferably said means responsive to light reflected back along the path of each beam comprises means provided between the source of each beam and the display area for directing reflected light towards a light detector whereby the output of the light detector provided for each beam will exhibit a decrease or negative pulse when that beam is obstructed by a probe.

Said retro-reflective reflector arrangement may comprise a continuous strip of retro-reflective material arranged to act as a reflector for both of said beams.

Preferably however a continuous strip of retro-reflective material is provided for each beam, each strip lying on a substantially circular path around part of the boundary of said display area whereby each beam, in operation, strikes its respective strip of retro-reflective material substantially normally. Preferably, said two strips are arranged one in front of the other, relative to said display area, and extend to cross one another.

Preferably the source of each light beam is a laser, in which case preferably each reflected light directing means comprises a mirror having an aperture therein through which the beam may pass on its way to the display area.

Preferably both beams are derived from a common light source by means of a light beam splitter.

Preferably each light beam is caused to sweep across the display area by means of a continuously rotatable mirror whereby each beam in operation sweeps across said display area, continues its rotation and commences to sweep across said display area again in the same direction.

Preferably the continuously rotatable mirror for each beam is arranged to rotate in operation in the same direction, and preferably again both beams are arranged to rotate in synchronised fashion.

Where a laser is used as light source, preferably this is a lower power HeNe laser.

Said display area may be occupied by a map, chart, table or other static display but preferably said display area is occupied by the screen of a television display apparatus which is arranged to display a screen viewed by a television surveillance camera.

Preferably a processor circuit is provided to convert scan angle positional signals derived from the detecting means to X and Y co-ordinate positional signals.

Preferably said processor circuit comprises for each beam and synchronised to the sweeping of that beam, a ramp waveform generator the output of which is arranged to be sampled and held by a sample and hold circuit when a probe obstructs the respective beam, the output of the sample and hold circuit provided in respect of each beam being connected to the input of an analogue to trigonometric converter providing four outputs in the form of Sin û, Cos 0; Sin (0 + O) and Sin Q (where (3 and < ) represent the respective angular orientations of the' two beams when each is obstructed by a probe) and an analogue 'transconductance arithmetical processor being arranged to convert said four outputs to X and Y co-ordinate signals.

The invention is further described with reference to Figures 1 and 2 of the drawings accompanying the provisional specification and Figure 3 of the accompanying drawing in which, Figure 1 schematically represents the mechanical features of one position resolving apparatus in accordance with the present invention Figure 2 is a block schematic diagram of a processor circuit which is provided to convert scan angle positional signals derived from the photo detectors 20 and 21 in Figure 1 to X and Y co-ordinate positional signals, and Figure 3 is a semi-schematic diagram illustrating a modification to the apparatus of Figure 1.

Referring to' Figure 1, the screen of a television display apparatus is represented in dashed line outline at 1. Upon this screen in operation will appear a scene viewed by a surveillance television camera (not shown). The requirement is to derive the co-ordinates of a target of interest in the displayed scene.

A strip 2 of retro-reflective material is provided in front of the screen 1 and extends along the bottom edge 3 and up the sides 4 and 5 of the screen 1. Mounted adjacent opposite top corners of the screen 1 are scanning mirrors 6 and 7 respectively, which are arranged to be rotated in the same direction (clockwise as represented by the arrows 8) in synchronism by means of the shafts 9 and 10 respectively. Mirrors 6 and 7 are so arranged that light transmitted along the optical axes 11 and 12 respectively will be deflected during rotation of the mirrors 6 and 7 so as to scan the length of the retro-reflective strip 2.

Light input from the scanning mirrors 6 and 7 is derived from a lower power HeNe laser 13, which is mounted with its optical axis aligned with the axis 12. Between the laser 13 and the mirror 7 is a beam splitter 14, which permits half of the light from the laser 13 to reach the mirror 7 and deflects the other half via a mirror 15 along the axis 11 to the scanning mirror 6.

The beam width of the laser 13 is narrow and positioned between beam splitter 14 and scanning reflector 7 on the one hand and mirror 15 and scanning mirror 6 on the other hand are two further mirrors 16 and 17, each having a central aperture 18 or 19 through which light from the laser 1 passes along the axis 11 or 12.

The purpose of apertured mirrors 16 and 17 is to direct light reflected back from the retro-reflective strip 2 and received via the scanning mirrors 6 and 7 on to a photo detector 20 or 21 respectively. Interposed between aperture mirror 16 and photo detector 20 on the one hand, and between apertured reflector 17 and photo detector 21 on the other hand is a focusing lens 22 and 23.

It will be appreciated that the light reflected back from the retro-reflective strip 2 on to the apertured reflectors 18 follows the same optical path as the light reflected on to the strip f 2 by the scanning reflectors 6 and 7.

The arrangement of the system shown in Figure 1 is such that the light reflected by scanning reflector 6 scans the length of retro-reflective strip 2 from the lower left hand corner 24 of the screen 1 to the top right hand corner of the screen 1, adjacent scanning reflector 8. Similarly, the light reflected by scanning reflector 7 scans the length of retro-reflective strip 2 from the lower right hand corner 25 of the screen 1 to the upper left hand corner of the screen, adjacent scanning reflector 6.

In operation with the mirrors 6 and 7 rotating in synchronism the two beams provided by the scanning reflectors 6 and 7 will sweep across the surface of the screen 1 and cause continuous reflections to be received by the photo detectors 20 and 21, which will therefore provide steady output except during approximately half of a complete cycle when the rotation of the mirrors 6 and 7 is such that the scanning beams are off the surface of the retro-reflective strip 2, i.e. during the part of the cycle when the beams have swept across the screen 1 and are continuing their rotation back to their points of origin at the beginning of a sweep across the screen.

If a pointer is placed anywhere on the screen, e.g. upon a target of interest, the photo detector output from each detector 20 and 21 will momentarily reduce due to the masking effect of the pointer. The position of the resulting "inverse" pulse within the output of each detector 20 and 21 will be directly related to the angular orientation of the respective scanning beam provided by the mirrors 6 and 7, and hence will be directly related to co-ordinates defining the position of the target upon which the pointer was placed within the viewed scene.

The angular orientations of the scanning beams provided by the mirrors 6 and 7 when each is masked by a pointer are designated 0 and < D respectively. The conversion of the scan angles 0 and Q > into X and Y co-ordinates follows the law: X = K sin Cos 8 sin (H + ) Cos 0 and Y = K sin Sin 0 sin (0 + q) where K is the distance between the optical centres of the scanning mirrors 6 and 7.

The processor circuit schematically represented in Figure 2, to which reference will now be made, is provided to effect the above mentioned conversion.

Referring to Figure 2, two ramp waveform generators 24 and 25 are provided, the first being synchronised with the rotation of scanning mirror 6 and the second being synchronised with the rotation of scanning mirror 7. The input leads for synchronising signals from shaft encoders (not shown) provided on scanning mirror drive shafts 9 and 10 are represented at 26 in the case of ramp waveform generator 24 and at 27 in the case of ramp waveform generator 25.

The outputs of ramp waveform generators 24 and 25 are connected respectively to sample and hold circuits 28 and 29. Sample and hold circuits 28 and 29 are controlled respectively by command signal generators 30 and 31.

Command signal generator 30 is connected to photo-detector 20 so that it operates sample and hold circuit 28 in dependence upon the time of occurrence of the previously referred to inverse pulse in the output of photo-detector 20, caused by masking of the beam from scanning mirror 6.

Command signal generator 30 is connected to photo-detector 21 so that it operates sample and hold circuit 29 in dependence upon the time of occurrence of the previously referred to inverse pulse in the output of photo-detector 21, caused by masking of the beam from scanning mirror 7.

Thus at the output of sample and hold circuit 28 appears an analogue signal representative of 0 and at the output of sample and hold circuit 29 appears an analogue signal representative of 4).

The outputs of sample and hold circuits 28 and 29 are applied to an analogue to trigonometric converter 32 provide four outputs 33, 34, 35 and 36.

On output 33 appears a signal representative of Sin 0 On output 34 appears a signal representative of Cos 0 On output 35 appears a signal representative of Sin (0 + ) On output 36 appears a signal representative of Sin 4 > The four outputs 33, 34, 35 and 36 of converter 32 are applied to an analogue transconductance arithmetric processor 37 providing two outputs 38 and 39.On output 38 of processor 37 appears a signal equal to:- K K sin Q, Sin 0 = X Sin (0 + ) On output 39 of processor 37 appears a signal equal to: K sin Q, Sin (H + ) Cos 0 = Y Referring to Figure 3, the modified apparatus illustrated thereby may be regarded as similar to that illustrated in Figure 1, except for the nature of the retro-reflective reflector arrangement.In the case of the apparatus of Figure 3, instead of the single continuous length of retro-reflective strip 2, two retro-reflective strips referenced 2a and 2b are provided, the former being positioned to reflect light directed onto it by scanning reflector 6 and the latter being arranged to reflect light directed onto it by the scanning reflector 7.

Strip 2a is mounted slightly in front of strip 2b, relative to the display area 1, and both are shaped to follow substantially circular paths around the boundaries of the screen area 1. As will be seen the two strips 2a and 2b cross each other below the display area 1. By providing two strips, one for each light beam, which are made circular, the light from each of the rotating mirrors 6 and 7 strike its reflector normally to the surface. This tends to ensure that the quantity of light received by each of the detectors 20, 21 (not represented in Figure 3) is substantially uniform over the scan area. With the arrangement illustrated in Figure 1, the strip 2 is not circular and the angle at which the light beams made the surface of the strip are subJect to variation which in turn results in the quantity of light received by each detector not being uniform over the scan area.

WHAT WE CLAIM IS: 1. A position resolving apparatus comprising means for sweeping two light beams across a common display area, a retro-reflective reflector arrangement arranged to surround at least part of the boundary of said display area and in the paths of said beams after they have crossed said display area and means responsive to light reflected back along the path of each beam for detecting when, in time relation with its sweep, each beam is obstructed by a probe placed at a position of interest in said display area to provide positional information relation to the position of said probe.

2. An apparatus as claimed in claim 1 and wherein said light beams are visible light beams.

3. An apparatus as claimed in claim 1 or 2 and wherein said means responsive to light reflected back along the path of each beam comprises means provided between the source of each beam and the display area for directing reflected light towards a light detector whereby the output of the light detector provided for each beam will exhibit a decrease or negative pulse when that beam is obstructed by a probe.

4. An apparatus as claimed in any of the above claims and wherein said retro-reflective reflector arrangement comprises a continuous strip of retro-reflective material arranged to act as a reflector for both of said beams.

5. An apparatus as claimed in any of the above claims 1 to 3 and wherein said retro-reflective reflector arrangement comprises a continuous strip of retro-reflective material provided for each beam, each strip lying on a substantially circular path around part of the boundary of said display area whereby each beam, in operation, strikes its respective strip of retro-reflective material substantially normally.

6. An apparatus as claimed in claim 5 and wherein said two strips are arranged one in front of the other, relative to said display area, and extend to cross one another.

7. An apparatus as claimed in any of the above claims and wherein the source of each light beam is a laser.

8. An apparatus as claimed in claim 7 and wherein each reflected light directing means comprises a mirror having an aperture therein through which the beam may pass on its way to the display area.

9. An apparatus as claimed in any of the above claims and wherein both beams are derived from a common light source by means of a light beam splitter.

10. An apparatus as claimed in any of the above claims and wherein each light beam is caused to sweep across the display area by means of a continuously rotatable mirror whereby each beam in operation sweeps across said display area, continues its rotation and commences to sweep across said display area again in the same direction.

11. An apparatus as claimed in claim 10 and wherein the continuously rotatable mirror for each beam is arranged to rotate in operation in the same direction.

12. An apparatus as claimed in claim 10 or 11 and wherein both beams are arranged to

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (19)

**WARNING** start of CLMS field may overlap end of DESC **. of processor 37 appears a signal equal to:- K K sin Q, Sin 0 = X Sin (0 + ) On output 39 of processor 37 appears a signal equal to: K sin Q, Sin (H + ) Cos 0 = Y Referring to Figure 3, the modified apparatus illustrated thereby may be regarded as similar to that illustrated in Figure 1, except for the nature of the retro-reflective reflector arrangement.In the case of the apparatus of Figure 3, instead of the single continuous length of retro-reflective strip 2, two retro-reflective strips referenced 2a and 2b are provided, the former being positioned to reflect light directed onto it by scanning reflector 6 and the latter being arranged to reflect light directed onto it by the scanning reflector 7. Strip 2a is mounted slightly in front of strip 2b, relative to the display area 1, and both are shaped to follow substantially circular paths around the boundaries of the screen area 1. As will be seen the two strips 2a and 2b cross each other below the display area 1. By providing two strips, one for each light beam, which are made circular, the light from each of the rotating mirrors 6 and 7 strike its reflector normally to the surface. This tends to ensure that the quantity of light received by each of the detectors 20, 21 (not represented in Figure 3) is substantially uniform over the scan area. With the arrangement illustrated in Figure 1, the strip 2 is not circular and the angle at which the light beams made the surface of the strip are subJect to variation which in turn results in the quantity of light received by each detector not being uniform over the scan area. WHAT WE CLAIM IS:
1. A position resolving apparatus comprising means for sweeping two light beams across a common display area, a retro-reflective reflector arrangement arranged to surround at least part of the boundary of said display area and in the paths of said beams after they have crossed said display area and means responsive to light reflected back along the path of each beam for detecting when, in time relation with its sweep, each beam is obstructed by a probe placed at a position of interest in said display area to provide positional information relation to the position of said probe.
2. An apparatus as claimed in claim 1 and wherein said light beams are visible light beams.
3. An apparatus as claimed in claim 1 or 2 and wherein said means responsive to light reflected back along the path of each beam comprises means provided between the source of each beam and the display area for directing reflected light towards a light detector whereby the output of the light detector provided for each beam will exhibit a decrease or negative pulse when that beam is obstructed by a probe.
4. An apparatus as claimed in any of the above claims and wherein said retro-reflective reflector arrangement comprises a continuous strip of retro-reflective material arranged to act as a reflector for both of said beams.
5. An apparatus as claimed in any of the above claims 1 to 3 and wherein said retro-reflective reflector arrangement comprises a continuous strip of retro-reflective material provided for each beam, each strip lying on a substantially circular path around part of the boundary of said display area whereby each beam, in operation, strikes its respective strip of retro-reflective material substantially normally.
6. An apparatus as claimed in claim 5 and wherein said two strips are arranged one in front of the other, relative to said display area, and extend to cross one another.
7. An apparatus as claimed in any of the above claims and wherein the source of each light beam is a laser.
8. An apparatus as claimed in claim 7 and wherein each reflected light directing means comprises a mirror having an aperture therein through which the beam may pass on its way to the display area.
9. An apparatus as claimed in any of the above claims and wherein both beams are derived from a common light source by means of a light beam splitter.
10. An apparatus as claimed in any of the above claims and wherein each light beam is caused to sweep across the display area by means of a continuously rotatable mirror whereby each beam in operation sweeps across said display area, continues its rotation and commences to sweep across said display area again in the same direction.
11. An apparatus as claimed in claim 10 and wherein the continuously rotatable mirror for each beam is arranged to rotate in operation in the same direction.
12. An apparatus as claimed in claim 10 or 11 and wherein both beams are arranged to
rotate in synchronised fashion.
13. An apparatus as claimed in any of the above claims and wherein a lower power HeNe laser, is used as a light source.
14. An apparatus as claimed in any of the above claims and wherein said display area is occupied by the screen of a television display apparatus which is arranged to display a screen viewed by a television surveillance camera.
15. An apparatus as claimed in any of the above claims and wherein a processor circuit is provided to convert scan angle positional signals derived from the detecting means to X and Y co-ordinate positional signals.
16. An apparatus as claimed in claim 15 and wherein said processor circuit comprises for each beam and synchronised to the sweeping of that beam, a ramp waveform generator the output of which is arranged to be sampled and held by a sample and hold circuit when a probe obstructs the respective beam, the output of the sample and hold circuit provided in respect of each beam being connected to the input of an analogue to trigonometric converter providing fouroutputs in the form of Sin 0, Cos 0; Sin (H + 4)) and Sin (where O and Q, represent the respective angular orientations of the two beams when each is obstructed by a probe) and an analogue transconductance arithmetical processor being arranged to convert said four outputs to X and Y co-ordinate signals.
17. A position resolving apparatus substantially as herein described with reference to Figure 1 of the drawings accompanying the provisional specification.
18. A position resolving apparatus substantially as herein described with reference to Figure 3 of the accompanying drawing.
19. An apparatus as claimed in any of the above claims and including a processor circuit substantially as herein described with reference to Figure 2 of the drawings accompanying the provisional specification.
GB982577A 1978-02-01 1978-02-01 Position resolving apparatus Expired GB1575420A (en)

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Cited By (36)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4507557A (en) * 1983-04-01 1985-03-26 Siemens Corporate Research & Support, Inc. Non-contact X,Y digitizer using two dynamic ram imagers
FR2563015A1 (en) * 1984-04-11 1985-10-18 Illinois Tool Works Radiation energy distribution and detection arrangement
US4558313A (en) * 1981-12-31 1985-12-10 International Business Machines Corporation Indicator to data processing interface
EP0183951A2 (en) * 1981-12-31 1986-06-11 International Business Machines Corporation Apparatus for determining the coordinate location of a manually movable object on a surface
EP0204436A1 (en) * 1985-05-24 1986-12-10 Wells-Gardner Electronics Corp. Light distribution and detection apparatus
FR2583159A1 (en) * 1985-06-05 1986-12-12 Illinois Tool Works Optical position location device
US4642422A (en) * 1985-12-16 1987-02-10 International Business Machines Corporation Calibration of a scanning light interrupt type of data input interface
EP0221712A2 (en) * 1985-10-21 1987-05-13 International Business Machines Corporation Data processing input interface
US4772763A (en) * 1987-08-25 1988-09-20 International Business Machines Corporation Data processing information input using optically sensed stylus features
FR2615309A1 (en) * 1987-05-11 1988-11-18 Dale Electronics Touch panel system
FR2630222A1 (en) * 1988-04-19 1989-10-20 Sfena Device for detecting projectiles
US4980547A (en) * 1985-05-24 1990-12-25 Wells-Gardner Electronics Corp. Light distribution and detection apparatus
US5434370A (en) * 1993-11-05 1995-07-18 Microfield Graphics, Inc. Marking system with pen-up/pen-down tracking
US5583323A (en) * 1993-11-05 1996-12-10 Microfield Graphics, Inc. Calibration of graphic data-acquisition tracking system
US5585605A (en) * 1993-11-05 1996-12-17 Microfield Graphics, Inc. Optical-scanning system employing laser and laser safety control
EP0897161A1 (en) * 1997-08-07 1999-02-17 Fujitsu Limited Optical scanning-type touch panel
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US8089462B2 (en) 2004-01-02 2012-01-03 Smart Technologies Ulc Pointer tracking across multiple overlapping coordinate input sub-regions defining a generally contiguous input region
US8094137B2 (en) 2007-07-23 2012-01-10 Smart Technologies Ulc System and method of detecting contact on a display
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US8274496B2 (en) 2004-04-29 2012-09-25 Smart Technologies Ulc Dual mode touch systems
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US8339378B2 (en) 2008-11-05 2012-12-25 Smart Technologies Ulc Interactive input system with multi-angle reflector
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US8432377B2 (en) 2007-08-30 2013-04-30 Next Holdings Limited Optical touchscreen with improved illumination
US8456418B2 (en) 2003-10-09 2013-06-04 Smart Technologies Ulc Apparatus for determining the location of a pointer within a region of interest
US8456451B2 (en) 2003-03-11 2013-06-04 Smart Technologies Ulc System and method for differentiating between pointers used to contact touch surface
US8456447B2 (en) 2003-02-14 2013-06-04 Next Holdings Limited Touch screen signal processing
US8508508B2 (en) 2003-02-14 2013-08-13 Next Holdings Limited Touch screen signal processing with single-point calibration
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Cited By (48)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4558313A (en) * 1981-12-31 1985-12-10 International Business Machines Corporation Indicator to data processing interface
EP0183951A2 (en) * 1981-12-31 1986-06-11 International Business Machines Corporation Apparatus for determining the coordinate location of a manually movable object on a surface
EP0183951A3 (en) * 1981-12-31 1986-10-22 International Business Machines Corporation Apparatus and method for determining the coordinate location of a manually movable object on a surface
US4507557A (en) * 1983-04-01 1985-03-26 Siemens Corporate Research & Support, Inc. Non-contact X,Y digitizer using two dynamic ram imagers
FR2563015A1 (en) * 1984-04-11 1985-10-18 Illinois Tool Works Radiation energy distribution and detection arrangement
EP0204436A1 (en) * 1985-05-24 1986-12-10 Wells-Gardner Electronics Corp. Light distribution and detection apparatus
US4980547A (en) * 1985-05-24 1990-12-25 Wells-Gardner Electronics Corp. Light distribution and detection apparatus
FR2583159A1 (en) * 1985-06-05 1986-12-12 Illinois Tool Works Optical position location device
EP0221712A3 (en) * 1985-10-21 1990-08-29 International Business Machines Corporation Data processing input interface
EP0221712A2 (en) * 1985-10-21 1987-05-13 International Business Machines Corporation Data processing input interface
US4762990A (en) * 1985-10-21 1988-08-09 International Business Machines Corporation Data processing input interface determining position of object
EP0227958A1 (en) * 1985-12-16 1987-07-08 International Business Machines Corporation Apparatus and method for locating an object
US4642422A (en) * 1985-12-16 1987-02-10 International Business Machines Corporation Calibration of a scanning light interrupt type of data input interface
FR2615309A1 (en) * 1987-05-11 1988-11-18 Dale Electronics Touch panel system
US4772763A (en) * 1987-08-25 1988-09-20 International Business Machines Corporation Data processing information input using optically sensed stylus features
FR2630222A1 (en) * 1988-04-19 1989-10-20 Sfena Device for detecting projectiles
US5434370A (en) * 1993-11-05 1995-07-18 Microfield Graphics, Inc. Marking system with pen-up/pen-down tracking
US5583323A (en) * 1993-11-05 1996-12-10 Microfield Graphics, Inc. Calibration of graphic data-acquisition tracking system
US5585605A (en) * 1993-11-05 1996-12-17 Microfield Graphics, Inc. Optical-scanning system employing laser and laser safety control
US5623129A (en) * 1993-11-05 1997-04-22 Microfield Graphics, Inc. Code-based, electromagnetic-field-responsive graphic data-acquisition system
US5665942A (en) * 1993-11-05 1997-09-09 Microfield Graphics, Inc. (Softboard, Inc.) Optical-scanning system employing laser and laser safety control
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