United States Patent [191
`Ebeling et a].
`
`[54] INFRARED LIGHT BEAM X-Y POSITION
`ENCODER FOR DISPLAY DEVICES
`[75] Inventors: Frederick A. Ebeling, Dearborn,
`Mich.; Roger L. Johnson,
`Monticello; Richard S. Goldhor,
`Champaign, both of Ill.
`[73] Assignee: University of Illinois Foundation,
`
`'
`
`Urbana, Ill.
`Feb. 28, 1972
`[22] Filed:
`[21] Appl. No.: 229,870
`
`'
`
`[52] US. Cl. ........... .. 178/18, 250/833 HP, l78/6.8
`[5]] Int. Cl ........................................... .. G08c 21/00
`[58] Field of Search ....................... .. 178/68, l7, 18,
`178/19, 20; 340/173 LT, 173 PL, 173 CR;
`250/833 HP, 83 UV; 35/9 R
`
`[56‘]
`.,
`
`3,614,439
`
`References Cited
`UNITED STATES PATENTS
`Treseder ............................ ..
`Beelik, Jr...
`..... .. 250/833 HP
`
`10/1971
`
`3,654,389
`
`4/l972 Pole . . . . . . . . . .
`
`. . . . . . . . . . . . . . .. 178/18
`
`3,493,754
`
`3/1970
`
`Black ......................... .. 250/833 HP
`
`[111 3,77%,@
`[451 Nov. 27, 1973
`
`OTHER PUBLICATIONS
`494, Vol. 9, No. 5, Oct. 1966, IBM Technical Disclo
`sure Bulletin, “Light Beam Matrix Input Terminal,” P.
`Betts.
`
`Primary Examiner—Kat_hleen H. Claffy
`Assistant Examiner—-Kenneth Richardson
`Attorney-Charles J. Merriam et a].
`
`ABSTRACT
`[ 5 7]
`A crossed light beam position encoder including x and
`y coordinate arrays of paired infrared light sources
`and detectors for covering a display device surface
`with x and y crossed light beams, scanning means cou
`pled to the sources and detectors for electronically se
`quentially scanning the x and y arrays so that only one
`source is emitting light and its associated detector is
`detecting light at any particular time. Means are in
`cluded for noting the digital address
`of the beams dur
`ing sequential scanning and for stopping the scan
`when the beams are interrupted, the digital address
`and therefor the position of the broken beams are
`transferred back to a computer‘
`
`13 Claims, 3 Drawing Figures
`
`34
`sounrcr/nsrzcron /
`SCAN CONTROL (X )
`
`
`
`SOURCE / DETECTOR \J scA/v CONTROL (Y)
`
`Samsung USP 7,973,773
` Exhibit 1013 Page 1
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`PATEN
`TEDHOWYIBIS
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`SHEET 1 OF 2
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`SOURCE/DETECTOR /34
`SCAN CONTROL (x)
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` Exhibit 1013 Page 2
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` Exhibit 1013 Page 3
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`

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`1
`INFRARED LIGHT BEAM X-Y POSITION
`ENCODER FOR DISPLAY DEVICES
`
`2
`mation schemes, generally involving lenses to produce
`the required beam collimation.
`
`3,775,560
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`35
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`45
`
`This invention relates to position encoder apparatus
`and in particular to infrared light beam position encod
`ers for display devices.
`Input devices used in conjunction with a computer
`control display for interactive information exchange
`between man and computer, via display, generally
`function as position encoders, that is, light pens, Rand
`Tablets, etc. Numerous devices and techniques that
`can be used to accomplish this task have been reported
`in the literature, such as the following:
`1. A.M. I-Ilady, “A Touch Sensitive X-Y Position En
`coder for Computer Input,” AFIPS FJCC Proc.
`Vol. 35, 545‘, 1969.
`2. RJ. Fitzhugh and D. Katsuki, “The Touch Sensi
`tive Screen as a Flexible Response Device in CAI
`and Behavioral} Research,” Behavioral Research
`Meth. and Instru., Vol. 3 (3), page 159, 1971.
`3. R.K. Marson, “Conducting Glass vvTouch-Entry
`System”, Society of Information Display Digest of
`Technical Papers, May 1971.
`.
`'
`4.
`Davis and T.O. Ellis, “The RAND Tablet: A
`25
`Man~Machine Communication Device,” AFIPS
`FJCC Proc. Vol. 26, p. 325, 1964.
`5. “Crossed Light Beams Bridge Operator/Display
`Interface,” Electronics, Oct. 11, 1971.
`Although many of the devices such as illustrated in the
`aforementioned literature can be used with various dis
`play devices, such as plasma display panels, cathode
`ray tubes, etc., they are generally very expensive and
`would not be used where low cost is an overall system
`requirement.
`.
`As an example of the low cost requirement, reference
`may be made to US. Pat. No. 3,405,457 wherein there
`is disclosed a computer controlled teaching system
`which includes a display device at each student station.
`The system therein illustrated is capable of servicing at
`least 32 student stations although this is by no means
`a limitation since current designs for such a system
`specify 4,000 stations, each of which would include a
`display device. Because of the large number of display
`devices in such a system, and the application of such a
`system to the educational ?eld, it becomes extremely
`important to meet low cost system requirements, par
`ticularly where it is desired to add to the system an x-y
`position encoder for each. display device.
`Several primary objectives can be defined:
`1. The device must encode absolute positions indi
`cated by the user.
`2. The input surface must be superimposed upon the
`display surface and provide for a minimum of par
`allax.
`3. Positions are to be indicated with a passive stylus,
`in particular, the human ?nger.
`Although crossed light beam systems have been dis
`cussed in earlier literature (see literature list, item 2
`above), such systems are extremely expensive, the ex
`cessive costs being due to the complex nature of the
`photosensing portion thereof. The complex nature of
`such systems is mandatory to assure that light from a
`particular source arrives only at its associated detector
`and does not impinge upon other nearby active detec
`tors. Thus, in such prior crossed light beam systems it
`is necessary to construct rather elaborate optical colli
`
`SUMMARY OF THE INVENTION
`A crossed light beam position encoder in accordance
`with the present invention includes x-y coordinate ar
`rays or sets of paired light sources and detectors for
`covering the display device surface with x and y crossed
`light beams. Prior requirements for beam collimation at
`all of the sources and detectors has been eliminated in
`the present invention by activating only one source/de
`tector pair at a time, that is, the x and y array of sour
`ce/detector pairs is electronically scanned so that only
`one source is emitting light and its associated detector
`is detecting light at any particular time. The digital ad
`dress of the beams are noted during sequential scan
`ning.
`'
`If a broken beam is detected during this scanning op
`eration, the scan is stopped at that point and the digital
`address (or position) of the broken light beam is trans
`ferred back to the computer. After this operation is
`completed, the scanning operation is resumed. This op
`eration is of course completed for both the x and y
`arrays. Using this technique, the problems of optical
`cross talk are completely and simply eliminated with
`out the aid of complex collimation schemes. There is
`thus provided a low cost position encoder which can be
`used in conjunction with computer controlled displays
`to function as a position encoder.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a schematic illustration of the x-y position
`encoder in accordance with the present invention;
`FIG. 2 is a cross-sectional view of the mounting ar
`rangement for the 16 element x-y source/detector ar
`rays for providing a crossed light beam adjacent the dis
`play device surface; and
`FIG. 3 illustrates a 16 X 16 element x-y position en
`coder system with the necessary electronic scanner ap
`paratus in accordance with the principles of the present
`invention.
`
`DETAILED DESCRIPTION
`Referring now to FIG. 1, there is illustrated a display
`device 10 having a display surface 12. An x array of 16
`infrared sources 14 are mounted along one side of the
`display device and are paired with a corresponding x
`array of infrared light detectors l6 suitably mounted on
`the opposite side of the display device 12.
`A similar y array of paired infrared sources 18 and
`detectors 20 are mounted along the remaining two op
`posite sides of the display device as illustrated in FIG.
`1. Thus, 32 pairs (16 per x and y axis) are mounted
`around the perimeter of display panel 10.
`Reference may be made to FIG. 2 wherein there is
`illustrated the display panel 10 and the mounting
`blocks 22 and 24 containing the infrared sources and
`detectors. For ease of illustration, only a partial
`sec
`tional view is illustrated since the mounting for the
`sources and detectors along the x and y axis is substan
`tially similar.
`Thus, mounting block 22 mounted on or
`adjacent the surface 12 contains a series of passage
`ways 26 at one end of which there is mounted, for in
`stance, an infrared light source 18. Similarly, mounting
`block 24 on the opposite side of the display panel con
`tains a series of passageways 28 each having an infrared
`light detector 20 mounted at one end of the passageway
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`in mounting block 24 in order to provide for maximum
`noise protection from possible ambient sources of in
`frared emission near the display panel. addresses
`Since the use of light sources which emit in the visible
`part of the spectrum is undesirable from both a human
`viewer standpoint and because of ambient light noise
`problems, gallium arsenide LED’s (light emitting di
`odes, emitting at 900 nm) and infrared phototransistors
`are used as the source/detector pairs.
`As shown in FIG. 1, the paired arrays of 16 infrared
`sources and detectors on respective sides of the display
`panel are arranged so as to provide crossed light beams
`such as the x light beam 30 from source 8,, to detector
`D2, and the y light beam 32 from source SH to detector
`D“. The x source/detector scan control 34 electroni
`cally scans the .r sources and detectors in order to acti
`vate only one source/detector pair at a time so that only
`one beam along the x direction (such as beam 30) is
`present at any particular time. Similarly, a y
`source/detector scan control apparatus 36 is provided
`to electronically scan the y sources and the detectors
`to selectively activate only one source/detector pair at
`a time and provide only one beam along the y direction
`(such as beam 32) at any particular time. Thus the x
`and y arrays of source/detector pairs are sequentially
`scanned to provide corresponding crossing beams.
`Referring now to FIG. 3, there is illustrated an x-y
`position encoder for supplying the position in the form
`of a digital signal for computer input. The x and y
`arrays of paired infrared sources and detectors are ar
`ranged in connection with the display surface 12 as il
`lustrated in FIG. 1. As previously described, this system
`of sources and detectors can be used to detect the pres
`ence and position of a passive stylus, that is, the ?nger,
`when it is placed into the plane of the array. The pas
`sive stylus will block a suf?cient amount of light from
`the infrared source so that the signal output of the asso
`ciated light detector (the detector directly opposite this
`source) will be decreased by an electronically detect
`able amount. When a blocked light beam is electroni
`cally detected, this beam position in the array is con
`verted into a digital signal which identi?es the position
`of the beam to the digital system being used with this
`encoder. The array in FIGS. 1 and 3 provides a grid of
`45
`256 addressed positions which can be detected.
`The infrared light beams are sequentially scanned
`across the display surface 12 with an “effective” beam
`diameter of approximately 1/16 inch. This con?gura
`tion was selected on the basis of the typical ?nger diam
`eter, that is approximately 7/16 inch. Although it is ob
`vious that the technique can be extended to higher res
`olution grids, the particular application described here
`did not require a resolution greater than two positions
`per inch.
`A constructed embodiment of the present invention
`was utilized in connection with a plasma display and
`memory device similar to that shown in the D.L. Bitzer
`et al. US. Pat No. 3,559,190 for incorporation as a dis
`play device at each terminal in the teaching system of
`the aforementioned D.L. Bitzer US. Pat. No.
`3,405,457. On this plasma display, it is desired that the
`8 9% inches X 8 ‘é inches square display surface be di
`vided into 256 areas (a 16 X 16 matrix) which are sen
`sitive to the selection and/or touch of the human ?nger.
`That is, the position or address of the area which is se
`lected by pointing or touching of the human ?nger is
`automatically sent back to the central computer system
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`65
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`in a manner similar to that used to send back key set
`information. The present infrared position encoder
`combines very effectively with the plasma display panel
`because the display surface can also function as a rear
`projection screen for projecting additional information
`onto the display surface.
`While the present embodiment of the present inven
`tion is herein described in respect to its application to
`a plasma display and memory unit, it is to be under
`stood that the application thereof is not so limited and
`can as well be applied to other types of display devices,
`such as cathode ray tubes, solid state displays, etc.
`The need for optical collimation is eliminated in the
`present system by activating only one source/detector
`pair at a time in the x and y arrays. Since the LED‘s and
`phototransistors exhibit rise and fall times of 2-5 mi
`croseconds, large numbers of source/detector pairs can
`
`be scanned within time intervals which
`correspond to
`human ?nger reaction times. For example, if each sour
`ce/detector pair is turned on for a 100 microseconds,
`than a source/detector array of 100 pairs could be
`scanned in 10 milliseconds.
`Sensing the presence and absence of the source pro
`duced light beams is achieved with a phototransistor
`that is matched to the LED emission. The signal pro
`duced by currently available type of phototransistors,
`however, is much too small (approximately 100 milli
`volts) to be detected with a standard logic unit and as
`a result must be ampli?ed. Since a detector has need
`for an ampli?er only once per scan and since no two
`detector signals need to be ampli?ed at the same time,
`only one multiplexed ampli?er
`is needed per x and y
`array.
`The circuit blocks used to perform the scanning,
`sensing and control functions of a 16 element x and y
`array are shown schematically in FIG. 3. The logic units
`used were of standard TTL type.
`In general, the scanning, sensing and control func
`tions are accomplished by electronically scanning the
`x and y arrays sequentially while keeping a record of
`the particular x and y address of
`the selectively acti
`vated source/detector pair in each array. The display
`surfaces are scanned from top to bottom and from left
`to right as shown in FIG. 3. Upon interruption of the
`light beams, the particular x and y address of the sour
`ce/detector pairs in the x and y arrays are noted and
`transferred to the computer. The apparatus providing
`such functions and operations are shown in FIG. 3. In
`particular a free running clock 40 operates through line
`42 to operate the x counter 44 and y counter 46 so as
`to sequentially select the address designations for each
`of the 16 source/detector pairs in the x and y arrays.
`Each of the x an y counters 44, 46 contains a four bit
`counter for specifying the digital address of each of the
`16 associated paired sources and detectors.
`Respective x and y decoders 48, 50 contains suitable
`logic gating circuits for decoding the respective four bit
`addresses from the x and y counters into one of the as
`sociated 16 lines. Each of the decoders 48, 50 is nor
`mally inhibited through respective inhibit lines 52, 54
`for a preset delay time following
`the sequencing of a
`new address in the counters. This delay time eliminates
`the possibility of errors arising from noise erroneously
`gating the infrared sources and detectors through the
`decoders. As shown in FIG. 3, the output of the decod
`ers is coupled into the respective x and y arrays of
`paired sources/detectors. Thus, during the time the x
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` Exhibit 1013 Page 5
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`and y decoders are inhibited on lines 52 and 54, the IR
`sources and the detectors are inactivated. Following a
`new clock pulse to reset the counters 44, 46 to the next
`at and y address, and following a short delay to elimi
`nate the aforementioned noise gating possibility, the
`respective four bit digital addresses in the counters are
`transformed by the decode circuits to operate the cor
`responding x and y infrared sources.
`To insure that the respective corresponding detectors
`are receiving only the infrared light beam from the
`paired source, activation of the respective x and y
`detectors is delayed for a short time by delay circuits
`56, 58. This delay time corresponds to the normal acti
`vation time for the infrared sources and detectors so as
`to insure that they are fully turned on, and normally
`amounts to approximately vlOO microseconds. An x
`signal detector ampli?er 60 and a y signal detector am
`pli?er 62 are connected to the respective plurality of x
`and y infrared phototransistor detectors 16 and 20. The
`outputs of signal ampli?ers 60 and 62 are coupled to
`the respective x and y counters to provide suitable sig
`nals to stop the counters in the event the respective
`light beams have been interrupted. If a light beam is in
`terrupted, the x and y counters are stopped at the re
`spective, corresponding four bit
`digital addresses and
`these addresses are then read out into output register
`64 which is coupled to the computer to present the ad
`dresses in digital form to the computer input.
`Thus, during operation of the system shown in FIG.
`3, in the event there is no interruption of the crossed
`light beam on the display surface 12, the free running
`clock 40 keeps resetting counters 44, 46 to the respec
`tive four bit addresses of the associated l6 sourceslde~
`tectors in the x and y arrays. The respective sources
`and detectors are therefore sequentially selected from
`top to bottom and from left to right, and sequentially
`activated through the
`associated decoders 48, 50. In
`the event there is an interruption of a light beam, such
`as of beam 32 (see FIG. 1), the electrical output of the
`associated infrared detector would be coupled to y
`signal detector ampli?er 62 and present a STOP-Y sig
`nal to y counter 46. This locks the y counter at the asso
`ciated y address of beam_32. Assuming that the x beam
`had not yet been interrupted, the .r array would still be
`sequentially scanned until for instance beam 30 was in
`terrupted thereby presenting a STOP-X signal to x
`counter 44 to lock this counter at the particular x
`address. The x and y digital addresses would be loaded
`into output register 64 and. then transferred to the com
`puter input.
`The address information is used by the computer for
`various purposes which are beyond the scope of the
`present application. In general, some form of feed back
`indication from the computer would be coupled to the
`display. Audio feedback could also be provided if de
`sired.
`If the operator now lifts his ?nger from the display
`surface so that both beams 30 and 32 are no longer in
`terrupted, the x and y counters are reset and the se
`quential scanning of the display surface continues
`again.
`While the scanning and control apparatus has been
`illustrated herein in block diagram form, such appara
`tus is well known to those skilled in the art and can
`readily be constructed. In a constructed version of the
`present invention, the various logic units illustrated
`were of the standard TTL type. Various other forms of
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`the logic units can be provided such as described in
`“Pulse and Digital Circuits” by .I. Millman and H.
`Taub.
`Thus, the basic advantages of the present invention
`over existing schemes are low cost and the absence of
`optical collimation apparatus and additional layers,
`grids or surfaces which must be placed in the optical
`path of the display. Furthermore,
`it is to be understood
`that although the present application has been de
`scribed in connection with application to a plasma dis
`play and memory unit, the present x-y position encoder
`can, in addition, be used in numerous other display ap
`plications which require touch input capability.
`The foregoing detailed description has been given for
`clearness of understanding only, and no unnecessary
`limitations should be understood therefrom, as modi?
`cations will be obvious to those skilled in the art.
`What is claimed is:
`1. An x-y coordinate position address encoder for
`display devices comprising:
`an array of a plurality of infrared sources and detec
`tors mounted in a paired manner along respective
`sides of said display device to provide respective
`crossing beams in the x and y coordinate directions
`adjacent the surface of said display device;
`means, coupled to said plurality of infrared sources
`and detectors, for sequentially activating pairs of
`said sources and detectors for beam scanning the
`surface of said display device in the x direction
`while simultaneously sequentially activating pairs
`of said sources and detectors for beam scanning the
`surface of said display device in the y direction; and
`address means for responding to an interruption of
`said crossing beams and providing the x and y ad
`dress of the position of said interruption.
`2. An x-y position address encoder for display de
`vices comprising:
`a plurality of paired x infrared sources and detectors
`arranged to provide infrared beams along the x
`coordinate direction adjacent the surface of said
`display device;
`a plurality of paired y infrared sources and detectors
`arranged to provide infrared beams along the y
`coordinate direction adjacent the surface of said
`display device;
`sequential timing control means selectively coupled
`to said plurality of x andy infrared sources and de
`tectors for sequentially operating coresponding
`pairs of x infrared sources and detectors, while se
`quentially operating corresponding pairs of y
`infrared sources and detectors;
`said x and y sources when sequentially operated pro
`viding intersecting infrared beams sequentially
`scanning the surface of said display device;
`said sequential timing control means including 1: and
`y address counters, including means for denoting
`the x and y address of the particular pairs of x and
`y infrared sources and detectors when sequentially
`operated; and
`stop address means coupled to said x and y address
`counters and including means responsive to an in
`terruption of said intersecting infrared beams for
`stopping said counters at the corresponding x and
`y position addresses.
`3. An x-y position address encoder for display de
`vices as claimed in claim 2, wherein said x and y
`address counters further includes means for denoting
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`the x and y digital address of the particular pairs of x
`and y infrared sources and detectors during sequential
`operation.
`4. An x-y position address encoder for display de
`vices, as claimed in claim 3, including storage means
`for storing said 2: and y digital addresses corresponding
`to said interrupted infrared beams, said storage means
`including a register having respective portions thereof
`coupled to said x and y address counters for respec
`tively storing said x and y digital addresses.
`5. An x-y position address encoder for display de
`vices comprising:
`an array of a plurality of paired infrared sources and
`detectors arranged to provide intersecting infrared
`beams along a ?rst direction (x) and a second di
`rection (y) adjacent and along the surface of said
`display device;
`said infrared detectors providing a respective output
`signal upon interruption of the associated infrared
`beam;
`x and y counters including means for specifying the
`respective digital addresses of each of said paired
`infrared sources and detectors associated with said
`x and y directions;
`a clock coupled to said x and y counters for sequen
`tially setting said counters to said digital addresses;
`x and y decoder means respectively intercoupling
`said J: and y counters with said associated paired
`infrared sources and detectors;
`said x and y decoder means including means for se
`quentially selectively operating said paired infrared
`sources and detectors in response to said digital ad
`dresses so as to sequentially scan the surface of said
`display device with corresponding infrared beams
`in the x and y directions;
`x and y signal amplifying means respectively coupled
`to said plurality of infrared detectors for amplifying
`said respective output signal presented thereto
`upon interruption of the associated infrared beam
`during sequential scanning; and
`means coupled to said x and y counters and to said
`x and y signal amplifying means for stopping said
`counters in response to said respective output sig
`nal at the digital address of the associated inter
`rupted associated infrared beams.
`6. An x-y position address encoder for display de
`vices according to claim 5, including an output register
`coupled to said x and y counters for storing the digital
`addresses associated with said interrupted beams.
`7. An x-y position address encoder for display de
`vices as claimed in claim 5, including means for dis
`playing operation of said selected infrared source cor
`responding to said digital address so as to prevent unde
`sired erroneous operation of said selected infrared
`source.
`8. An x-y position address encoder for display de
`vices as claimed in claim 5, including means for corre
`lating the operation of said selected infrared sources in
`response to said digital addresses sequentially speci?ed
`in said J: and y counters with the operation of said se
`lected infrared detectors.
`'
`9. An x-y position address encoder for display de
`
`8
`vices as claimed in claim 5, including means for reset
`ting said x and y address counters in response to the de
`tection of previously interrupted beams.
`10. An x-y coordinate position address encoder for
`display devices comprising:
`an array of a plurality of non-visible radiation sources
`and detector devices mounted in a paired manner
`along respective sides of said display device to pro
`vide respective crossing beams in the .r and y
`coordinated directions adjacent the surface of said
`display device;
`counter means, including means coupled to said plu
`rality of paired non-visible radiation sources and
`detector devices, for sequentially activating pairs
`of said sources and detector devices to scan the
`surface of said display device with said respective
`beams in the x direction while simultaneously se
`quentially activating pairs of said sources and de
`tector devices to scan the surface of said display
`device with said respective beams in the y
`direction; and
`address means for responding to an interruption of
`said crossing beams and providing the x and y
`address of the position of said interruption.
`11. An x-y coordinate position address encoder for
`display devices as claimed in claim 10, wherein said
`non-visible radiation sources comprise a plurality of in
`frared light emitting diodes, and wherein said detector
`devices each includes an infrared phototransistor.
`12. An x-y position address encoder for display de
`vices comprising:
`a plurality of paired x non-visible light sources and
`detectors arranged to provide non-visible light
`beams along the x coordinate direction adjacent
`the surface of ‘said display device;
`a plurality of paired y non-visible light sources and
`detectors arranged to provide non-visible light
`beams along the y coordinate direction adjacent
`the surface of said display device;
`sequential timing control means selectively coupled
`to said plurality ofx and y non-visible light sources
`and detectors for sequentially activating corre
`sponding pairs ofx sources and detectors, while se
`quentially activating corresponding pairs of y
`sources and detectors;
`said x and y sources when sequentially activated pro
`viding intersecting non-visible light beams sequen
`tially scanning the surface of said display device;
`said sequential timing control means including x and
`y address counters,
`including means for denoting
`the x and y address of the particular pairs ofx and
`y sources and detectors when sequentially acti
`vated; and
`means coupled to said x and y address counters and
`including means responsive to an interruption of
`said intersecting non-visible light beams for identi
`fying the corresponding x and y position addresses.
`13. An x-y position address encoder for display de
`vices as claimed in claim 12, wherein said non-visible
`light sources each comprises an infrared light emitting
`semiconductor device.
`*
`*
`
`*
`
`*
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`*
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`3,775,560
`
`25
`
`30
`
`45
`
`55
`
`65
`
` Exhibit 1013 Page 7