CA1196104A - Photoelectric input apparatus - Google Patents

Abstract

ABSTRACT
A photoelectric touch input panel has a plurality of crossed light beams which are broken by an object, the position coordinates of which are identified as outputs.
Two spaced apart beam surfaces are provided, and the inter-relationship between the beams in the two planes is em-ployed to distinguish between interrupting objects on the basis of their size, attitude, and velocity characteris-tics. The number of beams broken in any beam plane is counte- to determined the relative size of the object, or to determine the center line of the interrupting object.
The beams in any beam plane are selected in accordance with the relative significance of the various beams, and interrupted beams are pulsed more rapidly than non-interrupted beams. The light-emitting devices of the .
various beam planes are constructed as an integral unit.
The control system of the touch input panel is adapted for use in monitoring the size, shape, and activity of objects within a space defined by plural beam planes, independently of the touch input panel.

Description

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SPEC:[FICATION
The present invention relates to photoelectric input apparatus; more particularly, to touch input panels having a series of crossed light beams, in which the interruption of a pair of crossed light beams identifies the position ~f an object in the plane.
PhotQelectric touch input panels have been devel-oped which use a plurality of crossed light beams, arranged in sets of parallel beams in a single plane, to identify the approximate position of an object which breaks both of two crossing beams. Typically, such touch input panels are intended to be used in front of a display device such as a cathode ray tube, and the position of an operator's finger when it touches a spot on the cathode ray tube is detected by determining which two crossed beams are simul-taneously interrupted. At times, the touch input panel is used witha stylus ox other device in place of a finger.
The resolution with which the position of the finger or stylus can be determined is dependent largely upon the spacing of the parallel beams in the beam plane and the width of the finger or stylus. The beams must be spaced apa.rt by a distance which is small enough to insure break--ing at least one beam by the smallest size finger or stylus, and, accordingly, it is frequently the case that multiple beams are broken. In previous touch input panels, the output is produced by an indication of the first beam which is recognized as ~eing broXen, scanning from one direction toward the o~her (for example, from the top down), and this results i.n determination o a position which is not the position correspondiny to the center line ~g~

of the ~inger or stylus~ Accordingly~ it is desirable to provide a way of determining the approximate center point of the finger or skylus if more than one of a series o parallel beams is broken.
In previous touch input panels, it is possible for a relatively small foreign object, such as an insect, a raindrop or debris, to cause a false indication of an input by passing through the beam plane. It is, there-fore, desirable to provide a mechanism for discriminating against ~orelgn objects which happen to pass through the beam plane of the device.
In previous touch input panels, a relatively com-plicated arrangement is required for controlling operation of khe panel. It is desira~le to simplfy, as much as possible~ the logic and electronic circuits required in the u~e of the panel to enable the panel to be produced with as ~uch econ~my as possible, and to incrPase the reliability of the panel~
Previous touch input panels, while useful for determining the position of an object in a beam plane, are not capable of sensing any additional data rela~ing to such input, such as the velocity of approach of the ob~ect to~ard the touch panel. It is sometime~ desixable to be able to discriminate the velocity of approach o an object which lntersects the beams in the beam plane, in order to insure with gxeater certainty that an actua~ion of the touch input panel in an inkentional actuation by means o~ a fing~r or stylus, rather than an accidental operation. It is, therefore, also desirable ko provide some mean~ o~ sensing the velocity of approach of an 6~

~bject which intersects the beams and the beam plane.
Previous touch input panels are adapted to scan through the entire population of each set of beams on a sequential basis, and therefore each .individual beam is scanned relatively infrequently. This establishes a time interYal of uncertainty as to whether a beam is interruptsd or not. It is desixable to reduce this ti~e interval, and increase the scanning rate for one or more specific beams which are of greater significance, or which are more likely than others to be interrupted.
Previous touch panels are not well adapted to operatio~ in more than one mode. Typically, they operate in a point mode, in which points are identi~ied by decoding the X Y coordinates of a broken beam pair, without recogniz.ing additional points which may be leaiti-mate inputs until after a condition is recogn.ized in which no beam is broken. It is desirable to avoid this limita-tion and permit multi-mode operati.on of the touch panel.
Previous touch panels have not been well-adapted to recognize and detect more than one pair of interrup~ed ~eams at a time, which severelylimits the usefulness of the panel~ It is desirable to provide an arrangement in which a number of interrupted crossed beam pairs are reco~nized. This ~akes it possible to use touch input p~nel control apparatus to perform a variety of tasks such as sizing, space monitoring, and protection inter-lock activities, Previous touch panels have not been able to discriminate between touch inputs (by a finger or stylus) which mo~e normally to the touch panel. I~ is desirable to be able to distinguish between normal or skew approaches, particularly in applications where high resolution of the touch input is required.
Previous touch panels have been required to use comparator~ for determining, in each beam plane, whether a beam detected as being interrupted is different from the last detected beam. It is desirable to provide an arrangement which makes the use of such comparators, and other associated logic, unnecessary.
It is a principal object of the present invention to provide a to~ch input panel with means Eor determining the approximate cen-ter point of an object which intersects more than one ~eam of a plurality of parallel spaced beams in a beam plane~
I~ is another objec~ of the present invention to provide improved logic apparatus for decoding the position oE an object which is detected within a beam plane.
Anothex object of the present invention is to provide means for sensing the presence of a inger or stylus or other elongated object, and distinguishing such object from an object of shorter dimensions.
A further object oE the present invention is to provide means for determining the velocity of approach of an object which is detected within the beam plane, or a change in velocity of the object during its approach.
Another object of the present invention is to provide means for selectively scanning particular beams with increased frequency relative to the scanning of the beams.
A further object of the present invention is to proyide ~eans for scanning interrupted beams more fre-quently than non-interrup~ed beams.
Another object oE the present invention is to provide appar~tus for enabling the control apparatus of the present invention to function selectively in a point mode or in a stream mode.
A furtheî o~ject of the present invention is to provide apparatus for enabling the con~rol apparatus of the present in~ention to monitor plural pairs of crossed interrupted beams.
Another object of the present invention is to provide a plurality of beam planes and apparatus for counting the number of interrupted beams in each set of beams defining each beam planeO
A urther object of the present invention is to provide appara~us for sizing ohjects within a space defined by a plurality ~ beam planes.
Another object of the present invention is to provide apparatus for monitoring activity within a space ~0 defined by a plurality of beam planes.
A further object of the present invention is to provide apparatus for monitoring specific locations within a space defined ~y a plurality of beam planes and for inhibitinq operation of dangerous ins~rumentalities in response to detection of an interrupted beam pair at such location.
A further object of the present invention is to provide apparatus for detecting the approach ~f a finger or stylus toward a touch panel in a normal direction and discriminating against an angled approach, ~g~

A further ob~ect of the present invention is to provide an improved arrangement for mounting a plurality of LED's associated with a single beam plane.
According to a broad aspect of the present invention, there is provided in a photoelectric input device having a plurality of light sources and photosensitive devices defining a set of light beams, apparatus for energizing said light sour-ces one at a time, and detecting means for developing a signal in response to a beam which is interrupted at the time i-ts light source is energized, the improvement comprising counting means for counting a number of beams in said se-t which are interrupted.

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The invention will now be described in greater de~ail with reference ~o the accompanying drawings in which:
Pigure 1 is a perspective view of a portion of a housing of a touch input panel incorporating an exemplary embodimen~ of the present invention, illus~rating devices associated with plural spaced crossed beams in a principal beam plane and plural spaced beams in an auxiliary beam plane;
Figure 2 is a unctional block diagram of a control system for the appara~us of Figure l, illustrating the apparatus for detecting and counting the number of broken beams, ~or detecting the coincidence of beam interruption in ~he principal and auxiliary planes, anf for determining the velocity of approach of an object toward the principal beam plane;
Figure 3 is a perspective view of an alternative embodiment of the present invention, incorporating spaced X and Y beam planes;
Figures 4a-4c are views of arrangements for mounting a plurality of LED's or phototransistors;
Figure 5 is a functional block diagram of a control system for an alternative embodiment of the present invention, having t~o X beam planes spaced on opposite sides of a Y beam p].ane;
Figure 6 is a -functional block diagram of a control system for a further dmbodiment of the present invention adapted for cowlting the num-ber of consecutive interrupted ,~_ be~ms ln each beam plane and determining the address of the center line of the interrupting object;
Fig, 7 is a functional block diagram of another ~mbodiment of the present invention adapted for scanning back and forth in each beam plane across an interr~pting object, without scanni.ng beam paths which are remote from the intexrupting ob j ect;
Fig. 8 is a perspective view of another embodi-ment of the present invention adapted for monitoring a space defined by a plurality of beam planes;
Fig. 9 is a functional block diagram of a logic circuit used with the apparatus of Fig. 8; and Fig. 10 is a functional block diagram of a control circuit Eor enabling the apparatus of the present invention to be selected for stream mode or point mode operation.
Referring now to Fig. 1, there is illustrated in diagram~atic form a housing 10 which contains ~he control system ~or operating a touch input panel. The housing 10 has a central opeIling 12, and the housing 10 is adapted to be placed in relation to a display surace on the front of a display device 11, which may be a CRT or other dis-play device, so that a display is visible in the opening 12.
The opening 12 is bounded by ~wo side walls 14 (one of which is shown in Fig. 1) and upper and lower walls 16, One of the side walls 14 is equipped with a plurali~y of light emitting devices such as LED's or the like, and the oppo-site wall is equipped with a plurality of photosensltive devices such a.s phototransistors or the like. The photo-transistors are aligned with the LED's and are adapted to receive light generated by the LED~s. There ls a lens i` v provided or each o the LED~s to collimate the li~ht and foc~s it principally on one o the phototransistors on the opposite wall. The path between an LE~ and the phototransistor on the opposite wall upon which the LED's light ls focused i9 referred to as a beam. There are a plurality of ~uch beams which originate at one of the side walls 14 and terminate a~ the opposite side wall 14, and these beams are arrang2d in parallel spaced relationship so that a person or operator who tGuches a panel located behind the opening 12 will intercept one or more of the beams. The beams are arranged in a plane which is refer-red to as a beam plane~
A ~econd set of spaced parallel beams extends bet~een the upper ~d lower walls 16t with each o such beams having~a light-generating LED at one end and a phototransi~tor at the other end. The beams extending between the slde walls 14 are referred to herein as the X beams, and the beams extending between the upper and lower walls 16 are referred to as the Y bearns. The X and Y beams may be oriented in any direction with respect to the horizontal and vertical. The plane of the X beams is referred to as the X beam plane, and the plane of the Y beams i5 refexred to as ~he Y beam plane. When the X
beam plane colncides wi~h the Y beam plane, the plane is reerred to as the principal plane~
In the apparatus of Fig, 1, a principal plane is formed near the rear of the opening 12, with crossing X
beams and Y beams in that plane. An auxiliary X beam plane is spaced forwardly o the pxincipal plane, near the front o the opening 12. Its plane i~ referred to as ~J

the auxiliary plane, The location of the principal plane is identi~ied in Fig, 1 by the apertures in the lower wall 16 and the rearward line of apertures in the side wall 14. The forward line of apertures in the side wall 14 define~ the auxiliary plane, The auxiliaxy plane is spaced far enough from the principal plane so that a small foreign object which happens to be present in the opening 12 cannot intercept beams in both the principal plane and the auxiliary plane. Coincidence of principal and auxiliary beam interruption can, therefore, be used to confirm that an interrupted beam is not caused by a small ~reign objectO This feature is of particular value when the invention is used in environments such as aircraft cockpits, outdoor terminals, etc.
Foreign objects (such as insects) which are large enough to break beams in both the principal and auxiliary planes simu~taneously can be discriminated against on the basis of their characteristlc ~elocity of approach toward the principal beam plane r as descri~ed hereinafter. This is accomplished by determining the time interval between a beam interruption in the auxiliary plane and a beam interruption in the principal plane, and inhiblting the device fxom recognizing a valid input unless that interval confcrms to prescribed values.
The X beams in the auxiliary plane are hori~ontal-ly aligned with the X beams in the principal plane. This fact is mad~ u~e of in order to require that corresponding X beam~ in both the principal and auxiliary planes are interrupted simultaneously in order to recognize a valid input. This requires an operator to touch the panel at ~'10--the front of the display device 11 in such a way that his finger or stylus extends generally normally to the panel, as far~as the X beams are concerned. By dis-criminating against input~ which interrupt non-correspond-ing X bearns in the principal and auxiliary planes, theapparatus is~able to discriminate against fingers or styli which approach the panel in an oblique direction as far a5 the X beams are concerned. Since the only set of Y beams is in the principal plane, the finger or stylus may approach the panel at any angle which simultaneously intercepts corresponding X beams. If a higher degree of normali~y is desired, a second se~ of Y beams can be provided spaced from the principal plane in order to make the same coinoidence requiremen~ for the Y beams as has been described ~bove in connection with the X beamsO
~hen an extra ~ beam plane is pro~ided, it is desirable to space it ~rom both the principal plane and the auxil~
iary X plane,'~so that three planes are provided. Noting the time di~ference of beam interruption in each of the three planes~permits a determina~ion of a change in the velocity as~finger or stylus approaches the panel. In other words, the time difference between interception of -;~
beams ln the ~irst two beam planes is a function of the average velocity in that space, and the time difference between interruption of the beams in the second and third beam planes is a function of the average velocity in that space. The determination of the averaye velocities in two adjacent spaces permi~s an identification of certain type~ of movement of the operatox's finger or stylus. Thi~ may be used as a~ additional input from the touch input panel, and is at times very significant.

For example, if the veloci~y of a finger decreases more than usual as it approaches the panel, it may indicate a degree of uncertainty on ~he part of the operator as to what part of the panel is to be touched. Recognition of this fact may be employed to select an appropriate progra~ for ~he circums~ance. For example, when the touch input panel is employed with a programmed learning device, one gubsequent program may be selected when the response indicated by the ~ouch input i5 correct and certain, and a different program may be selected when the touch input is correct, but hesitant.
Referrlng to Fig. 3, an alternative embodiment o~ the present in~ention is illustrated. In the embodimeht o~ Fig. 3, there is one set of X beams and one set of Y beams, which have been separated so that there is no principal plane~ The separation of the X
and Y beam planes permits the apparatus to discriminate against small insects, and to calculate the difference in time between interruption of the beams in the two auxiliary planes. It is not capable of requiring that inputs be made in a direction normal to the panel, as is the apparatus of Fig. l, but has the advantage of greater simplicity.
Referring now to Fig. 2, there is shown a functional block diagram illustrating a control system which may be used with the apparatu~ of Fig. 1.
A clock pulse generator 20 i~ provided which pxoduces repetitive pulses~ The pulses produced by the generator 20 advance a counter 24, which funetions as a scan counter for the X and Y beam~. It is a binary c~unte~ ~nd in the illustration of Fig. 4 is a multi-st~e counter.~;~The output lines 26 from four stages of the counter 24~are four in number, as identified by the slash and the numeral 4. A larger ccunter (having si~
O~ more stages, fox example) may be used for larger panels and when greater resolution is desiredO The lines 26 are connected ~o four input terminals of a latch unit 23, which functions to latch the data presented on the llnes 26 when a latch signal appears on a line 30.
The latch outputs of the latch unit 28 are presented on a group of four lines 32 to a decode unit 34, which has sixteen outpu~ lines 36 connec~ed to individual LED's on .:
one ~ the ~îdè walls 14, to generate the X beams 35 A g~te pul~e;~referred to as the LED gate is supplied from a fifth~stage of the counter 24 to the decoding unit 34 over à`line 38, so that an LED selected by the decoding unit 34 ls fi~ed only for the duration of the LED gate pulse on the line 38~ Preferably, this duration ~s a relatively small period within each cycle of the highest ~requency output signal supplied to the output lines 26, so that the LED's operate with a low duty cycle ~. .
and hav~ relatively high light output in relation to the a~era~e power consumed by the LED's. This increases the ef~iciency and reliability o the LED's. rrhe output ~5 lines 32 ~re connected over lines 40 to a series of output terminals (not sho~n~ which identify the address of the LED and the beam being energized at any given time.
rrhese terminals may be connected to a microprocessor or othex computiny apparatus as an input.
Two of the four lines 32 are also supplied to a :.~ ~

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set of group select gates 33 for selecting one or another of several groups of phototransistors 35 tfour in the embodiment of Figure 2~. Of all of the phototransistors in ~he selected group, only one receives light from the LED which is energized a.t that time, so that the composite signal from a selected group of phototransistors reveals that the beam originated wi-th the LED currently being energized is not interrupted. This signal appears on a line 42, which leads to the input of a threshold detector apparatus 44.
A suitable threshold detector apparatus is described and claimed in the Carroll et al United States Patent No. 4,243,879 for Dynamic Level ShifterJ
issued May 12, 1981. When a signal is received on the line 42 which indi cates that a beam has not been interruptedl the threshold device 44 pro-duces a signal on a line 46. The line 46 is connected to the D input of the D flip-flop 48. The clock input of the D flip-flop is connected to the LED gate line 38, so that the flip-flop 48 is set a~ the tra.iling edge of th0 LED gate pulse on the line 38 if a non-interrupted beam signal has been received on the line 42. This sets the flip-flop 48 so that its Q
output is low.
ln its reset condi~ion, the Q output of the flip-flop 48 is high and this is conveyed to the line 30 which causes the latching operation of the latch unit 28, This causes the ou~put lines 32 of the latch unit 28 to manifest the address~of the last LED which was energized subsequent ~o receipt of a non interrupted beam signal on the line 42.
When a beam is interrupted, there is no signal ~ lw~

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pr~duced ~n the line 46, and the flip-flop 48 is reset ~t the end of th~ ~ED g~te pulse, I~ remains reset as long as that beam remains interrupted~ This causes the latch unit ~ to remain latched at the address of the LED associated wi~h the interrupted beam, a~d this address is made available to external devices over the line 40~ The line 60 is also connected by way of the line 62 to an external device, to indicate that an X
beam interruption has been recognized~
Since the latch unit 28 remains latched to the address of the LED associated with the interrupted beam, his LED is pulsed repeti~ively at the ~ED gate pulse ti~e by one o~ the lin~s 36 until a non-in~errupted beam si~nal is rece~Lved on the line 42. Scanning then resumes until the next~interrupted beam is found. The counter 24 ~ , runs continuously during this tlme, The output on the lines 40 continuously indicates the address of the LED
associated with the interrupted beam, and ~he signal on the line 62 indicates that it is an interrupted beam.
~ ~he same apparatus is repeated for the Y beams, using the same counter 24. A separake latch unit 66 is provided ~or the Y beams~ A separate threshold detecto~ 68 is~e~ployed for the phototransistors associated with the Y bea~s, and a separate output flip-flop 70 is ~l~o pxovided-~or the Y beams. Output lines 72 from the latch unit 66 identify the addres~ of an LED associated with an interxupted Y beam, and a signal from ~he flip ~lop 70 on a line 74 indicates tha~ the address i5 one of an inte~rupted beam, When both of the lines 62 and 74 are high, lt ~i~nifies that X and Y bea~s have both been `J ``. - ~

broken, and ~he coordinates of the two interrupted beams are available on the lines 40 and 72. The LED for ~he interrupted Y beam is repetitively pulsed, at the rate of the clock ~enerator 20, as described above in connec~
tion with the X beam, and this continues until the beam is recognized~a~ non-interrup~ed.
The continuous pulsing of the interrup~ed beams provldes a di~ferent pulsin~ rate for interrupted beams , , than ~r non-interrupted beams. Until a non-interrupted beam i~ recognlzed, each be~m is pulsed once for every sixteen cycle~;of the clock pul~e generator 20 (assuming ~, ~
a touch input;panel having sixteen X beams and sixteen Y
beams). ~hen~a beam is interrupted, however, the inter-rupted beam is pulsed once during each cycle of the clock pulse generator 20, sixteen times higher than formerly.
This p~ovide~a markedly increased ability of the appaxatus to d~tect when a touch input has been tPrminated.
This allcw`a ~ ~ ouch input panel of the present invention to be u~ed~ ~ `~ore rapidly than conventional touch 2n input panels,~hich cannot recogni~e the termination of touch inpu~until after as many as sixteen cycles of the clock;pul ~;gener~tor. The speed of operation ~chieved by~t~ apparatus of the present invention makes it possible ~r~ an operator to make multiple inputs in a poi~t mode`~by rapidly withdrawing and then repositioning ,~;, ;, his finger on the panel, and allows rapid finger motion in a stream mode,~ in which a succession of output coordinates is ~enerated without lifing the finger or stylus frorn the p~nely Because the n~o~lement of the finger away frQm the int~rrupted beam is recogni~ed almost instantly, it ls not nece~ary for the operator to withdraw his ~16;

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finger and wait ~or sixt.een çlock pulse cycles to go by before making another finger input, As thus far described, the apparatus of Fig. 2 may be employed with the apparatus of Fig. 3, in which there is only one set of X beams and one set of Y beams.
~n the apparatus of Fig. 1, a second set of X beams i~
required for the auxiliary plane, and the apparatus assoclated with the second set of X beams will now be described.
The LED~'s of the auxiliary plane are connected in com~on with corresponding X LED's in the principal plane, directly ~rom the X decode unlt 34. The outputs of the phototransistors of the auxiliary plane are treated separately~
Driving.the LEDIs of the principal and auxiliary X plane~ ~r~m~the same decode unit 34 efPectuates a saVings o~ ~trùcture, and permits a construction in which only a small~:~;additisnal amount of structure is required for the auxiliaxy X plane, A separate threshold detecting circuit 80 is provided for the auxiliary X phototransistors, and a ~lip-flop 82 is set by the trailing edge of the LED gate pulse when the;detector 80 produces a signal indicating that a beam is broken in the auxiliaxy X plane. An AND-~ts 84 i~ connected to the outpu~s of the flip-flops 48, 70 and 8~, so that when they are all ~et, as when a finyer or stxlu~ has interrupted corresponding X beams and ~t lea~ one ~ beam, an output is produced indicating th~t ~ nor~al ~nput i~ readyO
The X decode unit 34 operates to energize the LED ' s for both the principal and auxiliary X planes, so that cQ~responding beAms in both planes are energized simultane~uslyO Since the X latch was last set following detection of an interxupted beam in the principal plane, ~nly the interrupted beam in the principal plane and the corresponding beam in the auxiliary plane can be pulsed~ When both of those ~eams are broken, the flip-~lops 48 and 82 are both set, indicating that a finger h~s a~proached the panel normally as far as the X beams are concerned~
When a finger approaches the panel in a direction which does n~t intercept the same X beam in the principal and auxiliary planes, only the flip~flop 48 can be reset.
The outputs o~ this and ~he flip-flop 82 are ccnnected to two inputs~E an exclusive OR-gate 86, the output of which is connected ~o an input of an AND-gate 88. The second input of the ~ND-gate 88 is connected to the output of the flip-flop 70,which ls set when a Y beam is broken.
~hen the ~ND~te 88 is operated, a signal appears on an output line 90, signifying that a skew input is present.
A skew input~i~ one which breaks a Y beam, but does not break both o~the X beams. This output line can be employed to trigger a message on the Screen of ~he dis-pl~y device 11~ indic~ting ~o the operator that he must pl~ce his fin~er or stylus more normal to the surface ofthe panel.
A counter 92 is provided for measuring the time difference between the arrival cf a finger or stylus in the auxiliary and principal planes. It receives ti~iny pulse~ through an AND-gate 94 from a timing clock pulse source 96, providing that a flip-flop 98 is set. The flip~lop 98 is set by a slgnal on the line 100 from a monostable multi-vibrator 102. The multivibrator 102 furnishes a signal in the line 100 for a short period S after the flip~flop 82 is set, indicating that an object has arrived at the auxiliary plane. When the object ~rri~es at the pxincipal plane, the flip-flop 70 is set, and a short duration signal i5 produced by a second monostahle multivibrator 104 on a line 106 to reset the ~lip~lop 93. Accordingly, the counter 92 counts pulses ~rom the source 96 only for the period between interruption of the beam in the auxiliary plane up until interruption of the beam in the principal plane. The output o~ the counter is connected to a comparator 105 which compares the content o the counter with value stored in storage device 107~ If the content o ~he counter is less than the value stored in the storage device 107, an output line 108 is energized, otherwise, an output line 110 is energized. The output line 110 activates a comparator 112, which compaxes the output of the counter 92 to the value stored in a second stcrage device 114. If the content of the counter is larger than the value stored in the storage device 114, a line 116 is energized and other~ise~ a line 118 is energi~ed~ Accordingly, the ~5 QUtputs on lines 108, 116 and 118 indicate respec ively that the time betwe n int~xruption of the auxiliary and principal planes is less than Tl, is between Tl and T2, and is greater than T2. ~rhe line 116 is connected to ~ne input ~f an AND-gate 120, the other input of ~hich is connected to the output of the AND-gate 84.

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The output of the ~ND~gate 120 indicates a nor~al inPut within the speed range speci~ied by the time values T1 ar,d T2. Th~s output can be used to control selection of a program which can inform the operator, through the dis-play panel, that the input is not recognized because thespeed of mo~ement of the finger or stylus was too fast or too slow. Al~ernatively, the several outputs on lines 108, 116 and 118 can select programs of operations which are suitable to inputs which are made rapidly, or slowly. In self-teaching devices, this may be especially significant, because instruction progra~s may be chosen in response to whe~hex an input is delivered slowly and hesi.tantly~ ~r rapidly, with certainty. The gate 120 can be connected thxough an O~-gate to the lines 108 and 118 instead of~to the line 116, to discriminate against a ran~e of ~elscities corresponding to the time Tl and T2, The velocity discrlmination available by the sign~ls on the lines 108, 116 and 118 is usable to dis-~inguish hetween valid inputs through the use of a stylus or finger, or through the accidental presence of another relati~ely large object, such as a moth, which is large enou~h to bxeak beams in both the principal ~nd auxiliary planes.
Flg, 5 i~ a functional block diagram of an alternative ar~angement of the present invention having two separated X beam planes~ This gives ~hxee distinct pl~ne~, with two X beam planes and one Y beam plane. In the apparatus illustrated in Fig. 5, the Y beam plane is interposed between the two X beam planes which are ~20~

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referred to as Xl and X2.
The counter 24 is connected to the latch unit 28 in the same manner as described in connection with Fig. 2, for the Xl plane. A separate latch unit 200 ls provided for the X2 plane, and it is corlnected through a multi-plexer unit 226 to a decode unit 202, which provides six-teen output lines for separately energizing the sixteen LED's of the X2 plane. Since separate latch units 28 and 200 are provided for the two X planes, they are 10 capable of latching the address of two separate inter-rupted beams in the Xl and X2 planes, when they are inter-cepted by an object which is not moving normally to the panel, In this way, the interruption of the beam in eithex the Xl or X2 planes does not prevent the recogni-15 tion of the interruption of a non-corresponding beam in the other pla~e.
Three-~threshold detection devices TD and three output ~lip-flops are provided 48, 70 and 82, just as in the apparatus of Fig. 2.
The output o~ the flip--flop 82 is connected thxough a monos~able multivibrator 102 to set the flip-fl~p 98 and the output of the flip-flop 70 is connected through a monostable multivibrator 104 to reset the flip-flop 98~ It causes the counter 92 to be counted 25 up to a value corresponding to the time difference be-tw~en bea~ interruptions in the X2 plane and the Y plane.
The monostable multivibrator 104 is also con-nected to set a flip-flop 204, which is reset by a multi-~ibrator 206 energized by the flip~flop 48. While the 30 flip flop 204 remains set, an AND gate 208 is activated to pass pulses from the timing clock souxce 96 to a counter 2107 Accordingly, the counter 210 is counted up to a value corresponding to the time difference be-tween interrup~ion of beams in the Y plane and the Xl plane. The content of the two counters g2 and 210 is conveyed to a 3ubtraction unit 212, the output of which is connected to a comparator 214 which compares the result o the subtraction with the value stored in a storage device 216. An output line 218 identifies the sign of the difference, which indicates whether the velocity ls increasing or decreasing as an object approaches the panel, and two additional output lines 220 and ~22 indicate whether the time difference is greater or less than the time difference stored in the storage device 2160 If it is desired to produce outputs responsive to the relative change in velocities as a flnger or stylus approaches the panel, a dividing unit can be substituted for the subtraction unit 212, whereupon the result is not~khe dii~erence between the times, but the relative leng~h of the times. This result can be co~pared with a standard value stored in the storage unit 215,~ whereupon the signals on the output lines 220 and 222 indica~e whether the change in velocity is above or below a specified value. ~he signal on the line 218 would be produced in response to a comparison ~ith unity in a comparator (not shown) and would signify a condition of increasing or decreasing velocity.
The Various outputs available from the apparatus of Fig. 5 can be used in the same manner as described in w ~

connection with the apparatus of ~ 2, namely, to con-trol selection of programs, in response to the observed c~ndition~. ~n the apparatus of both Fig. 2 and Fig. 5, it is apparent that the counting, the subtraction or division~ and the compariso~ can take place by suitable programmin~ o~ a microprocesslng unit or other computer, in which the storage devices 107, 114, 216, etc. are contained in the computer's memory unitO
In any arrangement in which multiple X beams are e~ployed~ it is preferable to place the LED's for one X
beam plane and the phototransistors for the other X beam plane on a sin~le side 14 of the opening 12. The other LED's and phototransistors would then be placed in corres-ponding positions on the other side 14 of the opening 12, In this way, there is less likelihood of interference between the LEDIs of on~ beam plane and the phototransis-tors of the ~ther, When multiple Y beam planes are pro-vided, a corre~ponding arrangement is also desirable for the same reason.
In Fi5, S, and AND-gate 224 has its three inputs connected to the outputs of the flip-flops 48, 82 and 70, and produces an output when all three flip~flops are set.
Since the flip-flops 48 and 82 may be set due to th~
interruption of non-correspondin$ beams, the output of the gate 224 doe~ not necessarily indicate a normal input, but does indicate that an input is readyl and that it is lon~ erlough to intexcep'~ all three beam planes. The presence of a normal input can be identified, however, b~ me~ns of apparatus which will now be described.
The multiplexer 226 has two sets of inputs connected respective~l~ to the outputs Df the Xl latch 28 and the X2 latch 200. Its output lines 228 are connected to the X2 decode unit 202, A con~rol line 230 is con-nected to the ~ultiplexer unit 226 ~or selecting the output of the Xl latch 28 or the X2 latch 200 to be decoded by the unit 202, Normally, the multiplexer 226 selects the output ~f the X2 latch, and when it does, the flip-:Elops 48 and 82 can be set by the breaXing of non--corresponding bea~s, When the condition cf the multiplexer 226 is chan~ed, howeyer, to select the output of the Xl latch 28 for use in the X2 decode unit 202, corresponding beams in the Xl and X2 planes axe pulsed simultaneously, and then the ~lip~1Ops 48 and 82 can be set only when corresponding beams are simultaneousl~ interrupted. An AND-gate 232`has two of its three inputs connected to the outputs ~f the flip-flops 48 and 82 and its third input to the multiplexer control line 230, Thus, when the multiplexer ~26 is caused to select the output of the Xl latch 28~ the gate 232 is enabled and produces an output when both the flip-flops 48 and 82 are set. With the multiplexer contr~l lines 230 high, this can occur only when corxesponding X bea~s are broken, so that t.he output Signi~ies that the input finger or stylus is normal to the touch panel Re~erence will now be made to Fig. 6, in which an embodiment is illustxated whi~h provides a means for countin~ the number of broken beams, and determining the center point o~ the object which is interrupting the be~ms, A clock pulse ~enerator 20 is connected to a counter 24, and the counter 24 is connected to X and decode units 34 and 67, just as described above in

-2~-relation to Fig 2. The coun~er 24 p~oduces an o-ltput on a line 311 at the end of each scan cycle. Since the apparatus provided for the Y beams is identical to that provided for the X beams, it will suffice to describe only the apparatus associated with the X beams, it being understood that this structure is duplicated for the Y
beam~.
The threshold detector 44 is con~ected to the flip flop 48. The flip flop 48 is reset when a beam is interrupted as has been described above Its output on the line 60 is connected to the set input of an RS flip-flop 302, which is set as the first interrupted beam is detected during each scan. A line 304 is connected to its reset input, and it is provided with a pulse on lS the line 311 at the end of each scan cycle for resetting it preparatory to a subsequent cycle of operation. The output of the flip-flop 302 is connected to the latch input of the latch 306, so that the output of the counter 24 is latched to identify the first interrupted be~m, when the first interrupted beam signal is received at the input of the flip~flop 48.
The output of the ~lip~flop 48 is also connected to a gate 308 which receives LED gate pulses at its other input. The output of the gate 308 is connected to the input of a counte~ 312 which is reset by a pulse on a line 311 at the end of each scan cycle. Accvrdingly, ~he counter is xeset to ~ero during ~he ea~ly portion of the scan cycle, and begins to count the LED clock pulses ~ollowing resettlng of the flip-flop ~8, and is incre-mented to a c~ntent of unity on the second interrupted beam. The counter 24 continues to be incremented by the clock pulse genera~or 20, so tha~ the decoder 34 con~
tinues to enexgize successive beams, after khe first intexrupted beam is detected. For each additional beam which is intercepted, th~ ga~e 308 produces an output which is counted by the counter 312. When the first following uninterrupted beam is recognized, the flip-flop 48 is set, and an input is applied from the line 60 through an inverter 314 to the control input of a latch unit 316, whereby the content of the ~ounter 312 is latched. The output of the inverter 314 is connected to one input of~an AND-gate 318, the other input of which is connected from the Q output of the flip-fl~p 302.
Since the 1ip-flop 302 is set following detection of the first interrupted beam, both inputs to the gate 318 are hi~h or the first time when the last of the series of interrupted beams has been detected. Its output on a line 320 si~nifies the end of a series of interrupted beams, The line 320 is connected to the control input of a shift unit 322 which is adapted to receive the data stored in t~e l~tch 316 and shift it rightwardly one position, which results in the binary quantity being di~ided ~y two. It is then output on lines 324 which are connected to one input of an adder unit 326~ The other input of the adder unit is connected to the output o the latch unit 306 by lines 328. The output of the adder appears on the lines 330, and represents the identi-fication of the first interrupted beam (stored in the latch 306) increased by half the number ~tored in the counter 312. It thus ldentifies the midpoint of the sequence of interrup~ed bearns which have been broken.
It is possible by this means to attain very high resolu-tion with the touch input panel by closely spacing the beams in the bea~ plane, even when the beams are broken by a fi.nger which is large in width compared to the inter-beam spacing.
The outputs which are available from the apparatus of Fig. 6 are the identification of the center line of the finger or stylus (on the lines 330), an indication that the interrupted beam series has ended (on the line 320~, and an indication that the X beam has been broken (on the line 60). These signals may be used as interrupt and data signals for a microprocessor, to enable the microprocessor to receive and process the information. Since a duplicate structure is provided for the Y axis~ it is convenient to provide an AND-gate similar to the AND-gate 84 of Fig. 2 to indicate that an input is ready~when both the X and Y operations have been completed, such input identifying the X-Y coordinates of ~o the center point of the interrupting object. This 5ig-nal may ~e produced by anding the line 320 with the cor~esponding output line ~or the Y beams.
It will be apparent that in the apparatus of Fig. 6 t it i5 necessary to continue scanning the X beams after the first interrupted beam is detected, in order to count the total number of interrupted beams. In the apparatus of Fig. 6, the counting continues ~or a full cycle, so that the increased pulslng speed of beams detected a~ having been interrupted, described in con nection with Fig. 2, is not a ~eature of Fig. 6. The -~7-apparatus o~ Fig. 6 can be modified, however, to enable the direction of sca~ning ~ reverse when the t~tal number of .interrupted beams have been ~canned, to improve the speed of operation of the apparatus. Such a modifi-cation is shown in Fig. 7.
ln the apparatus of Fig. 7, the clock pulsegenerator 20 is connected to two separate counters 352 and 354 ~or the X and Y beams. Both counters are up down counters, and the direction of coun~ing is separately controlled by a control line in each case. The control line for the X counter 352 is th~ line 353.
Th~ clock pulse generator 20 counts the counter 352 up~ardly, via a frequency divider 355, which produces the LED g~te pulses7 The content of the counter is decoded by the X decoder 34 to energize the LED's for the X beams.
The output of the phototransistors is connected to the X
threshold detector 44, and operates the flip-flop 48. This rnuch of the operation is similar to that which has been already desc~ibed above. ~he Q output of the flip-flop 48 is connected to the toggle input o~ a flip-flop 358.
This sets the ~lip-flop 358 and causes the latch unit 306 t~ be latched to hold the address o the interrupted beam, A ~ate 360 is connected to the Q output of the flip-flop 48 and ~o the LED ga~e pulses fox causing the counter 312 to count the n~nber of interrupted bearns.
It recPives a third input from the Q output of a flip-flop 361, The function of the 1ip-flop 361 ls to control the dixectio~ of counting of the counter 352. This ou~put is high wh~n the counter is counting upwardly in its normal direction, so that the counter 312 is enabled t~
count the interrupted beams which are encountered after the first in~errupted beam, while the counter is counting in its nor~al upward direct.ton The Q output of the flip-:Elop 48 is connected to the toggle input of the flip-flop 361. The Q output of the flip flop 48 goes high when the first non-interrupted beam is encountered following a series of interrupted beams, and this causes the flip~flop 361 to be reset.
The resetting of the flip-flop 361 disables the counter 31~ and causes the counter 352 to begin to count downwardly, and therefore again scans the inter-rupted beams in the reverse direction. When th~ first inte~rupted beam is reached, the flip-flop 48 is reset, and its Q output goes highO This output sets the flip-flop 358 to terminate the output ready signal. When all of the interrupted beams have been scanned, e~entually, a non-interrupted bea~ will be reach~d, and at that time, the flip-~lop 48 is set and its Q output goes high.
This sets the flip-flop 361, to resume upward counting of the counter 352. The flip-flops 48, 358 and 361 are resotred to their initial condition at the beginning of the scan~ The Q output of the flip-flop 358 operates to reset the counter 312 o~er a line 313, preparatory to makin~ a new count ~ the number of interrupted beams on the next successive scan. The output of the counter 31 is conn~cted to the latch 316, which is operated by inverter 364~ Which receives its input from the Q output vf the flip-flop 361~ Accordingly, th~ latch 316 is operated after the full set of in~erruPted beams ha.s been scanned and the flip~flop 361 is reset in order to cause the counter 352 to count downwardly. An AND-gate 366 has its inputs connected to the output of the inver-ter 364 and the Q output of the flip~lop 358 to identify that a count is ready. The content of the latch is pre~erably shif~ed by means of a shifter as shown in Fig. 6 and added to the data stored in the latch 306, in the manner described in connection with Fig. 6 to identif~ the center line of the operating finger or stylus.
The flip-flops 358 and 361 are reset and set, respectively, by the pulse on the line 311 whenever the end of scan i5 reached, to insure that their operation remains synchron-ized.
The apparatus of Fig. 7 operates faster than that of Fig. 6, because it scans only the interrupted beams backwardly and` forwardly and pxovides an output of the center line of the interrupting object during each upward scan~ Although, in the apparatus of Fig. 7, the data which might be acquired during downward scans is ignored~ it will be appreciated that the apparatus can be modified to make use of this data as well. Such a ~odification would involve latching in the latch unit 306 the hiyhest address of an interrupting beam (at the end of the upwaxd scan or beginning of the downward scan), resetting the counter 312 at the beginning of the down-ward scan, counting the number of interrupted beams dur-ing the do~nward scan, shifting the data stored in the counter at the end of the downward scan and subtracting it from the data in the latch 306 to arri~e at the identification of the center line of ~he interrupted beam.
It is apparent that other latches (not shown) may be provided for holding data so that valid outputs are ~30-'.~ 1 `

available to an output de~ice without any particula~need for synchronization with the opera~ion sf the upward and downward scanning apparatus.
It will ~e appreciated that, in the arrangement of Fig. 7, similar structure is provided for the Y beams, and an ~N~-gate can be pro~ided 'co and ~he data ready outputs of the X and Y circuits to identify when the X
and Y coordinates of the center point of the interrupting object are availa~le for read-out to an external device.
Referring now to Fig. 4a~ a perspective diagram is illustrated of a plurality of active elements which may be either ~ED's or phototransistors, which are fabricated in the fo.rm of a single in~egrated structure, on a strip 378, Several or all of the elements may be fahricated as integrated circuits formed in a single semiconducting surface. A plurality of indi~7idually light-emittinq areas 380 are provided in spaced relation-ship along the length ~f the device, and a plurality of pins 382 protrude from the bottom of the appara~us in order to enable easy mounting and replacement of the structure~ The ~abrication of plural LED's on a single structure makes it possible to control the accuracy of the spacin~ of the LED at the time of the manufacture of the LED uni~s themselves, and substantially decrease the assembly spexations req~ired in construction of a to~ch panel appa~atu~.
Abo~e the strip 378, a second strip 384 is positiDned. It is formed of transparent plastic material, ~nd it has a plurality of positive lenses 385 integrally m~lded thereinto, spaced apart by distances which ` ~J ~_ ~ ~3 ~

correspond to the sp~cing o~ the LED~ 380~ The lenses 385 comprise ~onvex surfaces on the upper surface of the strip 3841 while the lower surface of the stxip 384 is planar. The thickness of the strip is such that when it is laid directly on the strip 378, the lenses 385 are positioned relative to the LED' 5 to allow for maximum focusing of the light em.itted therefrom. The use of the lenses 385 in association with the LED effects a sufficient collimation so that the light from any one LED is principally focused on a single phototransistor.
This makes it possible to select groups of spaced photo-transistors since only one of each selected group i5 illuminated by the LED which happens to be energized at any one time.~.;This avoids the necessity of energizing the LED ~ s and phototransistors in single layers~
Fig. 8 is a diagrammatic illustra~ion of a further embodiment of the present inVention in which the touch panel mechanism is employed to monitor a space~ A
space 408 is indicated diagrammatically in Fig. 8, and it is surrounded in three separate planes by three rectangular~ hollow housings 402, 404 and 406. The housin~s support liyht sources and photosensitive devices on opposite s1des, to form crossed beam planes, in the same manner which has been described above in connecti.on with touch input panels. In the embodimen~ of Fig. 8, h~wever, no touchable panel per se is employed. The apparatus is used to monitor activity within the space 408. The space 408 may, for examp:Le~ comprise an an:imal cage, in which case the apparatus of Fig. 8 is adapted to monitor the acti~ity of an animal in the cage. The v '~

beams which are broken in the X and Y directi~ns in all three planes can be observed to represent the profile of the animal within the space, distinguish between lying, sitting and standing attitudes of the animal, determine the horizontal position of the animal in the cage, and, in general r monitor its activity. The speed of movement of the ~nim~l in either the X or Y direction can be determined by noting the time difference between break-ing of successive beams in the beam planes. This is effectively accomplished by scanning back and forth across the animal, with the apparatus of Fig. 7 or as modified.to allow meaningful data to be generated scanning in both directions. The time diference between inter-ruption of successi~e beams in a beam plane is determined by employing counters as in Figs. 2 and 4, but triggering the counters on and off when successive beams become non-interrupted, The content of the counter is then inversely proportional t~ the velocity component trans-verse to the beam direction in the beam plane, When the direction of motion of the animal is not parallel to either ~et of beams, the speed of movement of the animal in any direction may be calculated by vector addition of the X and Y velocities.
In another application, the apparatus of Fig. 8 may be employed ~o monitor the ac-tivi~y of a child in a playpen or a crib. Although the space illustrated in Fig~ 8 i~ square, the space 408 need not be square, if ~he beams in the cross beam planes are not equally spaced, or if more beams are provided in one set of cross beams than in ~he o~her. ~n arrangement with an unequal number of beams in the beam plane is easily accommodated by ~ - /

~36~

the apparatus of the present invention, by use ~ the set inputs 581 58' and 58" (Fig 2) which enable the intercepted beam de~ecting flip-flops to be set externally, to ignore non-meaningful inputs which may be produced by the vaxious threshold detectorsO
~he apparatus of Flg. ~ ~ay also be used to monitor activity within a larger space, such as a room, where it may be desira~le to maintain a record of movement of people, animals, or objects The apparatus of Fig. 8 can also be employed to monitor movements within dangerous environments, in such a way as to prevent accidental injury. For example, when it is desired to monitor activi-ty around a machine ~ool, such as a punch press, or other metal forming or metal cutting machine, the space 408 lS defines the space around the machine in which an operator can stand during operation of ~he equipment. The apparatus of Figt 8 senses the position of the operator in relation to the machine, and may be used to inhibit operation of the machine when the operator or any part of the operatox moves into a dangerous position. The housings 402, 404 and 406 are positioned in such a way that the dangerous positions of the machine are scanned, and it is apparent th~t they need not necessarily be s~acked in parallel arrangement as shown in Fig. 8, if an angled relationship afords a better filling of danyerous areas with crossed beams. The presence of an operator's hand within a dangero~ls area is recognized by the coordinates of the beams which are in~errupted, and apparatus is provided ~or disablin~ the machinery when the interrupted beams axe recognized in these locations.

-3~-The appar~tus of Fi~. 8 may also be ernployed to grade or size objects which pass within the space 408.
This can be acco~plished by counting ~he total number of X beams broken by any one object, counting the total number of Y beams broken by any one object and multi-plying these numbers together to get a result which is the ~unction of the volume of an object which is entirely within the space scanned by the three planes of the appar-atus of Fig~ 3. Additional planes may be provided for greater resolution, if desired. For longer objects,the objects may be sized by moving through the space 408 with a uniform velocity. The cross ~ectional area of the ~bject may be determined in any of the three planes r by calculating the product of the total number of X
beams and Y beams which are broken, and integrating the cross sectional area by répetitivR addition while the object is moving through the space 408. It is apparent that only a single plane of crossed beams is required for this appli~ation.
~ The logic circuit associated with the structure of Fig, 8 is illustrated in Fig. 9. The clock pulse generator 20 is employed for producing pulses which count up a counter 412 Via a divider 355. The output of ~he counter is connected to a Y decode unit 414 and to an X
decode unit 416, for decoding the content of the counter 412 and energizing one of a plurality of LED's of other li~ht sources. Since ~he apparatus provided for the Y beam~ is identical to that for ~he X beams, a description of the apparatus provided for the X beams will ~u~ice for both, ~, The housing 402 ls shown in Fig. 9 in cross section~ and it is seen that an LED 418 is contained within the hollow housing aligned with an ape~ture ~hich has a colli~ating lens ~20 superposed over it. ~ligned with the LED 418 and the lens 420 is an aperture 422 in the opposite side ~all of the housing 402, and a photo-transistor 424 is posi~ioned behind the aperture 422.
The housing 404 and 406 for the other two planes ha~e a similar structure, but the central plane 404 has the position of its LED and phototransistor interchanged, to minimize interfe~ence between the LED's of one plane and the phototransistors ~f another. .Corresponding LED' 5 of all three planes are connected together so that no ~dditional lines from the X decode unit 416 are required for any numbe~ of planes which may be provided.
Each of the three planes has its individual inter~upted bea,m. recogniticn flip~flop 434, 436 and 438, connected to its threshold detector, so tha~ interruption o~ three correspondin~ beams in the three planes is independently reco~nized.
When~a~beam in the X3 plane is interrupted, the clQck input to the ~lip~flop 434 resets the flip-flop, and its Q QUtpUt goes high, giVing a hi~h leve.1. signal on the output 440, indicat.ing that ~he X3 beam has been interrupted. ~he line 440 i5 connected to the latch input o~ a l~tch unit 442 which has its data inputs connectecl to the output of the counter 412. Accordingly, the add~ess of the LED associated with the lnterrupted be~m in the X3 plane is latched in the latch unit 442 and is available ~s an output on lines 444. A gate 446 h~s ~.J v ~6~

its inputs conne~ted to the Q output o~ the flip-flop 434 and its clock input~ The gate g46 produces pulses which are counted in a counter 450. The counter 450 is reset by a reset pulse on a line 311 at the end of each scan cycle, and is counted Up from zero to count the total number of successive beams in the X3 plane which are interrupted. This output is available on lines 452.
Similar apparatus is provided for the output flip-flops 436 and 438 of the X2 and Xl planes, and the address of the first interrupted beam in these planes is available on lines 454 and 456, with the total number of sequential broken beams being available on lines 458 and 460. These various outputs are available to a CPU or other controlling device, which is adapted to select a specific program of 15 operation~ For example, if the cross sectional area, as seen in the three X beam planes, is ~o be calculated, the outputs of the three oounters, which are available on lines 45~, 453 and 460, may be added. If the apparatus is designed to determine whether an object is in a certain defined space (such a~ an operator's hand in a dangerous area around a machine tool), an inspection can be made of whether the X coordinate of the dangerous location is within the range~ indicated by (a) the outputs 444, 454 and 456 indicating the addresses of the first inter.-cupted beam in each plane, and (b) the outputs indicating the total number of sequential interrupted beams in the three planes, It is ~pparent that a microprocessor or other processing device can readily make this determination and i~sue an output signal which can halt operation of the machine when a danyerous condition is recognized.

~37-The apparatlls of Fig. 9 is also adaptable to control by an ex~rnal computer, in which case the scan-ning means may be energized in any sequence defined by the computer~s program. ~hen this mode of operation is desired, the computer contFols the voltage levels on lines 464 and 466~ The lines 464 are data lines, for setting the counter 412 in response to a control signal on the line 466, When the line 466 is high, the counter 412 operates independent~y of the clock pulses produced by the generator 20 and the divider 355. When the line 466 goes highr the counter 412 loads the data from the lines 464. This causes the counter 412 to be set to the data provided by the computer on the lines ~64~ so tha~
any desired beams ean be chosen by providing the appro-priate data on the lines 464. In this way, special progra~s may be executed ~ scan only areas of interest, such as d~ngerous positions around ~he machine tool, or other programs may be executed in which only the area occupied by a body or object is scanned, to reduce the response time of the appaxatus. Such a program has been described in connection with Fig. 7 r It is apparent that an MPU or other computer c2n be axranged ~o carry out, through software, the operation~ which are perform.ed by the hardware described in connection with Fig 7.
As described in the foregoing embodiments, the apparatus of the present invention i8 adapted to produce a stream o~ outputs corresponding to the beams which are interrupted at any gi~en time. Under some circumstances, it is desirable to cause the apparatus to operate in a poin~ ~ode~ in which an ou~put is produced identifying v the X-Y coordinates of only the first pair of crossed beams which are intercepted, No other data is output until a condition is first recognized in which no beams are interceptedO This mode of opera~ion is sometimes S desirable, in connection with a touch panel, when it is desired for the operator to execute operations in which only point~ are per~i~sible inputs.
An arrangement is illustrated in Fig. 10 in which the poin~ mode or the stream mode may be selected.
The threshold detectors for the X and Y planes are con-nected to the X and Y flip--~lops 48 and 70 in the manner described above. The Q outputs of both flip-flops are connected to inputs of a gate 502 to generate an output ready signal on a line 504 when both flip-flops have been reset, indicating the presence of interrupted X and Y
beams. The output of the flip-flop 48 is connected to the set input o~ a flip-flop 506 which functions to produce a signal which operates the X latch unit 28, making the address o~ the interrupted X beam available on the output 40. Similarly, the output of the flip-flop 70 is connected to the set input of a flip-flop 510, the Q output o~ which is connected to operate the Y latch 66 a,nd make the address of the in~errupted ~ beam avail~
able on the lines 72~ Once the flip-flops 506 and 510 have been se~, they cannot be reset until a signal is available on the line 514. Thls signal is developed by a NOR-gate 516 connected to the outputs of the flip~
flops 48 and 70, and resets the 1ip-flops through OR-gates 525 and 526. A pulse appears on the line 514 only when both o the flip-flops 48 and 70 have been set in response ~39-`` J

to recognition of a non-interrup'ced beam, Therefore~ the finger or stylus must be withdrawn so that no beam is interrupted before the la~ches 28 and 66 can indicate a suhsequent address.
W~len a stream mode is desired, a mode selec~or input 518 is brought low. This is connected to inputs of two NOR-gates 520 and 522, the output of which are connected through the OR-gates 525 and 526 to the reset inputs of the flip-flops 506 and 510. The other inputs of the NOR-gates S20 and 522 are connected to the Q out-puts of the flip-flops 43 and 70. Accordingly, when the line 518 is low, the flip-~lop 506 i~ reset immediately following recognition of a non-interrupted beam by the flip-flop 48~ When this occurs, the output of the flip-lS flop 48 ~oes Iow, and the garce 520 produces a pulse which passes through the gate 525 to rese~ the flip-flop 506.
~ccordingly, the X latch 28 may be latched as soon as the next interrupted beam is recognized. The same oper-ation occurs or th~ Y latch.
The circuit of Fig. 10 makes it possi~le easily to select a point mode of operation or a stream mode, so that either may be used, as desired.
Figs 4b and 4c show alternative arrangements for the integrated construction of active elements. In Fig. 4b, two rows 552 and 554 of active elements are fabricated on the same supporting surface 556, in spaced apart relationship. One row is made up of LED's and the other row i5 made up of phototransistors, to form halE
of the active elemen'cs needed for two spaced beam plhnes.
In Fig, 4c~ two ~heets oE transparQnt plastic material 384a and 384b are provided, separated by a spacer sheet ~'10--384c. The sheet 384c is formed of any convenient ma-teri~l 9 and positions the sheets 384a and 384b far enough apar~ so that the collimation effect of the lenses is enhanced as much as possible. The spacing of the lenses above the strip 378 is determined by the thickness of the sheet 384b.
The operation of the apparatus described herein is improved mar-kedly by the use of variable threshold devices which adapt to ambien~ light conditions in enabling the detection of interrupted and non-interrupted beams. Such devices are described and claimed in above-mentioned ~nited States Patent No. 4~243,879. The use of the variable threshold devices makes the interlocking and spacemonitoring operations of the present inYention possible. With previous apparatus, the high and variable light levels encountered during such operations would effecti.vely prevent collec-tion of meaningful data.
While the presen~ invention has been described above in relation to ;ts discrimination against small objec~s, where operation of a touch input panel by finger or stylus is desired, it will be apparent that large objects can also be discriminated against. For example~ if more than a given nuinber of consecutive beams in any beam plane are interrupted, the inter~ipting object may be recogni~ed as not a finger or stylus, and the input rejected.
The control logic described above has been described in most cases for posit;ve logic, i.e., a positive-going pulse i5 required to execute the indicated function. It is apparent -to those skilled in the art that pulses of opposite polarity may be obtained at substantially the same times by the use of inverters where required. Where clocked logical units are employed (such as synchronous countexs instead of ripple counters) a suitable source of clock pulses may be provided as well as understood in the art, All of the logic units illustrated and described are conventional commercially available units.
It will be appreciated by those skilled in the art that although the present invention is described in terms of beam planes, the various sets of beams are not necessarily aligned in a plane. In fact, when a curved surface such a~ a CRT is used as the display device of a touch input panel, the sets of beams are preferably curved to conoxm to the curved CRT surface. Moreover r the light beams referred to herein need not necessarily be beams of visible light, but mav be anv form of radiant energy, whether visible or invisible. For example, the energy may be invisible infrared energy.
In the oregoing, the present invention has been described suc~ as to enable others skilled in the art to make and use the same ~ithout departing from the essential features of novelty involved. It will be app~rent that vaxious modifications and additions may be ~ade without departing from the essential features of novelty, which are intended to be defined and secured by the appended claims,

Claims (6)

THE EMBODIMENT OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a photoelectric input device having a plurality of light sources and photosensitive devices defining a set of light beams, apparatus for energizing said light sources one at a time, and detecting means for developing a signal in response to a beam which is inter-rupted at the time its light source is energized, the improvement comprising counting means for counting a number of beams in said set which are interrupted.

2. Apparatus according to claim 1, including means for counting the number of consecutive interrupted beams in said set.

3. Apparatus according to claim 2, including means for developing a signal indicative of the center line of an object which interrupts more than one beam of said set.

4. Apparatus according to claim 3, wherein said photoelectric input device has means for defining a second set of beams oriented in crossed relationship to said first set, second counting means for counting the number of consecutively interrupted beams of said second set, and means responsive to said second counting means thereto for developing a signal indicative: of the center line of said object relative to the second set of beams.

5. Apparatus according to claim 3, including a second set of beams oriented in crossed relationship with said first set, means for counting the number of consecu-tive beams in said second set which are interrupted by said object and means for developing signals representa-tive of the area of an object in a plane parallel to the planes of said first and second sets by multiplying the number of interrupted beams of one set by the number of interrupted beams of the other set.

6. Apparatus according to claim 3, including a second set of beams, the beams of said first and second sets being oriented generally parallel to each other, with the beams of said first and second sets defining two spaced-apart surfaces, means for counting the number of consecutive beams which are interrupted by an object in each of said first and second planes, and calculating the cross sectional area of said object in a plane normal to both sets of beams by developing a signal indicative of the total number of interrupted beams in both sets.