US3825730A

US3825730A - Two-way projection system for data input

Info

Publication number: US3825730A
Application number: US00304554A
Authority: US
Inventors: H Worthington; E Rawson; D Schwarzkopf
Original assignee: Searle Medidata Inc
Current assignee: Searle Medidata Inc
Priority date: 1972-11-07
Filing date: 1972-11-07
Publication date: 1974-07-23
Anticipated expiration: 1991-07-23

Abstract

A data input terminal comprising a two-way projection system for the selection of desired input messages from a library of selectable messages. The library of messages is optically displayed in groups on a projection screen and selection of desired messages from the projected group is optically detected to provide electrical output signals representing screen locations corresponding to the selected messages.

Description

United st ates Pat ent/t 11 1 T Worthington, 'Jr, et all;

5111 3,325,730 {451 July 23,1974

I 4] TWO-WAY PROJECTION SYSTEM FOR 7 DATA INPUT Y [75] Inventors: Harvey R. Worthington, .lr.,

Concord; Edward B. Rawson, Lincoln; Daniel B. Schwarzkopf, V Stow, all of Mass. [73] Assignee: Searle Mediclata, lnc., Waltham, I Mass. I [22] Filed: Nov. 7, 1972 21 Appl. No.: 304,554

[52] US. Cl...:. 235/92 V, 235/92 R, 250/219 D,

. 340/324 R [51] Int. Cl. G06m 11/00 [581 Field of Search, 235/92 .V; 340/324 R; ,r y I I r I 250/219 Dj- [56] y References Cited UNITED STATES PATENTS, 3,534,359 I'D/1970 -Harris 340/324 R Prirrzkzry-Examiner-Paul J. Henon 1 Assistant Examiner loseph M. Thesz, Jr.

Attorney, Agent, or FirmWeingarten, Maxham &

Schurgin 57 ABSTRACT A data input terminal comprising a two-wzty projec- I tion system for the selection of desired input messages from a library of selectable messages. The library of 7 messages is optically displayed in groups on a projection screen and selection of desired messages from the projected group is optically detected to provide electrical output signals representingscreenlocationscorresponding to the selected messages. 3

' 14 Claims,6' Drawing Figures VERIFICATION COUNTER SELECTOR 28 SWITCHES ADDRESS STORAGE NEW "*C" AR CHAR CHAR- SELECTION CLEAR UTILIZATION (DELAY) PATENTEB JUL 2 3 I974 SLIDE SHEEI 10F '2 SELECTOR SWITCHES ADF 66 HQLD--- I DATA-M cHAR ADR HOLD- 68 FIG. 1

I 5 2 70 HOLD L CLEAR UTILIZATION SELECTION (DELAY) PATENTEB L SHEU 2 BF 2 4 FIG. 2

ELECTRONICS HILIIIIIIII LOAD COUNTER o oooooo MULTIPLEXER FIG. 5

HOLD

Two-WAY PROJECTION SYSTEM FOR DA TA INPUT s FIELD or THE INVENTION v This invention relates to data input terminals and in particular to terminals for the optical selection of input data from a library of information.

BACKGROUND OF THE INVENTION With digital information handling systems becoming more commonly used in all fields, increasing demand is being expressed for the provision of effi'cient data input terminals which permit the selection of input data from a large libraryof available inputs. In such applications it is necessary to both display for the operators selection the information from which he is permitted to select predetermined input messages and also to permit simple and foolproof communication to the input terminal of the operators data selection. i

In the rapidly expanding field of medical datasysterns, instances exist .for which'it is desirable to provide multiple data input terminals havingat low cost, flexibilities and capacities not previously available infthe prior art-systems. In one such application, information handling systems are provided in hospitals to process the flow of medical and administrative information. In such cases it is necessary to provide a plurality of information input terminals whereby, for example, individual nursing stations can call up orders or services for individual patients and select them from a vast body of possible medical requests. a

. Exemplary priorsystems which employ a switch matrix and overlay system have been found satisfactory for many applications but are limited in the size of the' input data library and often use mechanical switches to enable selection-of input data. Prior systems which luse a projection of selectable input data without switches for data selection require complex and expensive scanning systems to enable electro-optical separation of-different portions of the projected image for identifying the image area corresponding to selected data. One prior art attempt to provide this capability is shown in Harris, U.S. Pat. No. 3,534,359.

vast library of available input data is provided accordsing to'the present invention in an input terminal foruse.

with a medical information handling system. The information input terminal employs a fully optical datadisplay and selection system which permits rapid accessto,

and selection from the whole input data' library. The fully optical design is economical in the use of display area to increasethe possible library size and provides for input data selection without the use of costly me system onto a photodetector array with predetermined alignment between screen image locationsand detec-.

tors in the Iarraybut at an 7 to activate any detector in the arrayr'when the-operation of the system of FIG. 1;

2 optical intensity insufficient tor wishes to make a data input selection a light source is applied to the screen at a location corresponding to the selected data to cause an intense spot of light to be focused onto the detector array activating a corresponding detector. The detector array is scanned to tie termine the activated detector and a digital signal is generated to represent the activated detector. The array scanning and activated detector determination are made with provisions to reject spurious activations.

An additional,digital signal is generated to indicate which transparency is displayed and together, the two digital signals completely specify selected input information from a very large number of possible choices. The use of projectable transparencies for each repertory further facilitates modifications to the library of selectable inputs by simple replacement of one or more transparencies.

BRIEF DESCRIPTION or THE DRAWINGS These and other features-of the present invention will be more fully understoodby reference to the detailed description of preferred embodiments presented below for purposes of illustration, and not by way of limita tion, and to the accompanying drawings of which:

FIG. 1 is a pictorial and schematic diagram of a twoway projection system according to the invention;

FIG. 1A is a view of a typical information repertory projected by the system of FIG. 1:;

FIG. 2 is a diagrammatic view of the projection porscreen reflective pointer for FIG. 3 is a diagram of a modified projection for use in the invention with a data selection;

FIG. 4 presents a modification of the projection sys- 1 tem and reflective pointer for use in the invention; and

The feature of rapid selection of input data from a FIG. 5 isa pictorial and schematic diagramof a modified detector tion. v

DETAILED DESCRIPTION or A PREFERRED EMBODIMENT I To provide-a flexible, easy to use, and low cost input terminalfor selection of multiple choice input data a two-way projection system is shown in FIG. 1. Thecomponents indicated could typically be contained within a small console but are shown without reference to the console in FIG. 1 for clarity of understanding. In a rear projection system, a projection screen 12 is positioned to receivelight directed from a-projector 14 at a focal plane of the projected light. Light eminating fromthe rear projection surface of the screen 12 is focused by a lens system .16 onto the plane of an array of photodetectors 18. v

Theprojector- 14 may typically be any of the several available, externally programmable random access projectors such as, for example, the Kodak Carousel RA- 950 or RA-960 projector. The projector 14 has a magazine or tray 20 from which 80, or slides may be selected for projection in'response to externally applied control signals to be described below.

A typical slide repertory is indicated in FIG. 1A wherein an image 22 is shown to contain a plurality of selectable input messages 24 associated with selection points 26. The repertory of slide 22 might find typical and imaging system for use in the inven- 3 application in ahospital input terminal where it may be desired to provide to the hospital data system selected pharmacy or test orders pertinent to a particular patient@ This selection is made directly from a projected list of possible pharmacy or service instructions presented in the format 22. it is to be noted that more or less messages may be provided in the same repertory.

A selector switch system 28 is provided adjacent to the projection screen 12 for example when mounted in a console to enable the terminal operator to manually select which of the 80 or 140 slides is desired for dis play and accordingly for selection of particular information contained thereon. The output of the switch operates through the projector 14 to cause the magazine to be appropriately positioned for displaying that slide.

Selection of desired information from a displayed image 22 is achieved by illuminating a point 26 with the light spot from a small light source such as pen light 30.. The projection screen 12 will normally be of a translucent material which is sufficiently lightdispersive to provide a clear image of slides projected by projector 14 onto screen 12 and also sufficiently transmissive of light to transmit significant portions of illumination provided by the pen light 30 from the operators side of screen 12 to the reverse side facing the projector 14 and lens system 16. The pen light 30 and screen 12 are adapted to provide radiation of light from the back of screen 12 toward the'lens system 16 in a quantity substantially greater than diffused illumination from the projector 14 or from ambient room light. This may be facilitatedby not subjecting the points 26 to illumination from the projector and by employing a size for point 26 which corresponds to the detector size.

Typically the array 18 will contain a matrix of photosensitive transistors 32. The lens system 16 and array 18 are placed adjacent to the projector. 314 but slightly off axis from each other due to physical placement requirements. The photosensitive detector array 18 is positioned with the lens system 16 so that light from each selection point 26 is imaged onto a corresponding photosensitive transistor 32. The number of selection spots 26 which canbe .placed on a single slide will be generally limited by the abilities of the individual projector 14 to consistently position the projected'irnage.

As indicated in FIG. 1', the collectors of all transistors 32 in a single row are tied together and biased through a single resistor 34. All resistors 34 are supplied from a Single voltage source 36. Electrical connections are fed from each row at the point of junction with the collectors of transistors 32 to row output terminals of the array 18 which are in turn connected to a sampling, multiplexer circuit 38. Multiplexer circuit 38 provides at its output, each of the output signals specified by digital signals from a counter 40.

The emitters of all phototransistors 32 in a column are joined together and electrically connected externally of array 18 to a decoder circuit 42 which sequentially grounds the emitters a column at a time in response to a control input from counter 4h. The counter 40 continuously cycles through a predetermined count in response to clocking signals from an oscillator 44. Typically most significant bits from the counter 40 correspond to column addresses and are applied as the control signal to the decoder circuit 42 which, for each binary state in the most significant bits, grounds a corresponding column of emitters from the array 18. The least significant bits from the counter 40 are applied to the sampling circuit 38 to connect to a DATA output line 46 a corresponding one of its row inputs depending upon the binary state of the least significant bits.

The total binary count of the counter 40 is applied to an address storage register 48. The register 48 is caused to respond to and store the digital contents of the counter) by a LOAD input from an AND circuit 50. The AND circuit 50 receives the output of the multiplexer circuit 38 as well as a NOT HOLD input signal on a line 52. The NOT HOLD signal will he subsequently described, but generally indicates a system preparedness to accept new information. When both signals occur, the counter 4D is at a binary count which connects signals at the decoder 42 and sampler 38 to the row and column of an illuminated photosensitive transistor. The register 48 is loaded with the digital contents of the counter 40 at that time, this digital signal indicating which photodetector is illuminated. A comparator 54responds to the stored data in register 48 and the output of the counter 40 to provide an address output on a line 56 (ADR) in response to digital equality between its two inputs. As is apparent, circuit 54, according to conventional digital clocking techniques, will make its comparison of the previously stored counter signal with the about to be stored counter signal.

Toprovide a verification of the illumination of a photosensitive transistor 32 a verification counter 58 is provided to cause several sequential rapid samplings of thesamephotosensitive transistor 32 before acceptance of that indication as a valid input of data. To accomplish this an AND gate 60 receives the ADR signal from the line 56 and the DATA output on line 46 of multiplexer circuit 38 as well as the NOT HOLD signal on line 52 and a NOT CHAR signal to be explained.

(Coincidence of all four signals causes application of a signal to the count-up input of counter 58 causing it to advance one digital count. A further AND gate 62 receives theADR address output the HOLD signal, a NOT DATA signal derived from line 52 and the NOT CHAR signal. Coincidence of all signals causes the counter 58 to countdown a digital step in response to a signal applied to its count-down input from the gate 62; The counter 58 is preset through an OR gate 64 when either a signal is received from an AND gate 66 of an AND gate 68. The AND gate 66 receives a NOT ADR signal derived from the address signal on line 56 and the DATA signal on line 46, the NOT HOLD signal and the NOT CHAR signal; The AND gate 68 receives the same last two mentioned signals and ADR address signal on line-56 and the NOT DATA signal derived from line 46;.

The indicated NOT signals may be-derived from any of the known techniques including inverting outputs or inputs, or separate inverters.

It can be seen that the counter 58 is preset through the OR gate 64 if the DATA signal from the multiplexer circuit 38 is received at a time when the stored address in the register 48 is different from the state of the counter 40 as indicated by the NOT ADR signal and if the NOT HOLD and NOT CHARconditions exist. Similarly, if an ADR signal is preset with NOT DATAand the NOT HOLD and NOT CHAR signals exist, the counter 58 will be preset.

available from all slides in the magazine 20.

The counter 70 is causedto count up when boththe ADR and the" DATA signals arepresent providedthat NOT HOLD and NOTCHAR exist. After a sufficient digital count, the counter 58 provides a count-up complete signal to a hold register '70 and a new character register 72. This count-up complete signal will cause the hold register 70, typically a bistable memory circuit, to provide the I-IOLD signal on an output 52. This signal is applied as indicated above in the system. At the same time the new character register 72 responds to the count-up complete'signal .74- to produce a new character output signal CHAR on line 74 to indicate that the digital number in the register 48 represents the message selected for input through the terminal. This digital representation is available atoutput line 76 of register 48.

The CHAR signal-and data on line 76 are applied to a utilization device 78 which may be a data processing system fo'r a hospital. After receiving the dataon line 76, the utilization device 78, returns a clearsignal to reset the new character register 72. For purposes of understanding this invention the utilization device 72 may be viewed .asproviding a delayed clear output in response to the CHAR signal to reset the register 72.

I HOLD signal and establishthe NOTHOLD signal. This count-down function provides a predetermined delay after theacceptance of information and after the removal of the light spot as produced by the pen light 30 from the surface of the screen 12 to prevent acceptance of the sameiinformation twice unless it is purposely desired. r t

Along withkthe CHAR signal on line 74, a SLIDE KEY signalon line 80.from the switches 28 indicating the particular slidedisplayed on the screen 12 is ap plied to the utilization device 80. The slide and selection inputs on lines 76 and80 to the utilization device 78 provide complete information on the specific mes sageselected by the operator from the vast; librar Referring now to FIG. 2 a diagrammatic view of the two-way projection system is indicated showing the adjacent relationship of the projection optics with the detector and imaging optics. In-particular a lamp 82 is provided to direct light through a condenser system 84 and a slide transparency 86 to a lens system 88. Light from the lens system 88 is imaged on a translucent projection surface or screen 90. The projection surface90 may be a glass or plastic plate constructed as indicated above to provide the necessary degree of translucence for presenting an image of the slide as well as transmit ting light from the pen light 30. Preferably, the screen 90 is marked to indicate the locations of the selection points 26. This may be achieved with an opaque surface coating 92which is perforated with transparent portions 94 in areascorresponding to the selection points 26 and has translucent regions 96 in the area of 6 The light frornathe pen light .30 is imaged through transparent portions 94 by an optics system 98 onto a projection for message selections 24.

photosensitive detector array'100 which is in turn samback illumination from the projector with ahigh specular characteristic and by employing the qualities of the Fresnel lens to direct it toward the optical system 98. and the detector array 100 as shown in FIG. 2. By placing the mirror 112' on the plane coatedsurface 108 of the screen 90 proper axial alignment of the mirror 112 is insured; As'isapparent for the FIG. 3 embodiment, the slides will be, designed to provide illumination through points 26 to portions 110.

In FIG. 4 a further'modificationis indicated wherein a screen 114 is provided with a dispersive coating 116 similar to coating 108 and transparent portions 118 aligned with the points26. A corner reflectorl is provided for placement over the transparent portions 118 to reflect light from the projector backwards along its'path of incidence. The complete optical system is shown in FIG. 4 to include a beam splitter mirror'l22 in the path of illumination from projector 14 to screen 114. Mirror 122 passes'light fromthe projector 14 but reflects light returned by retroreflector l20through a lens system 124 to a detector array 126 for electronic sampling as indicated above. The screen 104 and mirror 112 of FIG. 3 may also be used in the FIG. 4 embodiment to replace screen 1.14 and 'retroreflector120.

zontal row l36. No detector is in both column 134 and row 136. Vertical slit 130 will cause a vertical bar of light to fall on array 138 for each selection, and that bar will illuminate a detector in row 136 corresponding to the column on the displayed repertory containing the selected message. Similarly, horizontal slit 132 causes a horizontal. bar of light which illuminates a detector in column 134 correspondingtothe displayed row containing the selectedmessage. I I I A counter has its most significant bits applied through a multiplexer 142' to sample the state of each of the photodetectors in the horizontal row 136. A multiplexer 144 is provided to sample the photodetectors in the column 134 in response to the least significant bits in counter 140. The

multiplexers

142 and 144 detect illumination of a detector in the row 136 and column 134 and apply respective signals indicative thereof three inputv conditions are met. Register 148 is similar toregister 48 of FIG. land stores the digital state of counter 140 The remaining circuitry may follow the pattern of FIG. 1. I

In place of

slits

130 and 132 in mask 128, discrete holes may be employed. Additionally, slits which do vnot cross may be employed and may be made wide to accept cylindrical lenses to increase the intensity of the bars of light.

With the above indicated projection andelectronic detection system it is possible to provide a library of selectable information for multiple choice question and answer purposes or selection of input data from a vast library of-possible inputs by providing a raster of selectable data on each of a plurality of transparent images. A particular image and the corresponding selection from that image are encoded to provide an output indication of the desired information and to provide verifi-.

cation for each selection. The terminal furthermore provides rapid entry of a vast amount of data with selections from a plurality of different slides by using a random access projector. Moreover, the problems of switch contact bounce are eliminated by using an optical system and multiple scan verification for responding to the selection of individual data from each display raster.

The library of selectable input information is easily altered by providing new transparencies and by changing the recognized information in the utilization device as for example by altering addressable look-up tables. The selection sequence may be made adaptive as by employing data-processing to define the repertory to display on the basisof past selections.

It will occur to those skilled in the art that in addition to the systemdisclosed above, further modifications and alternatives can be devised to implement the spirit of the invention and accordingly it is intended to limit the scope of the invention only as indicated in the following claims.

What is claimed is:

1. A two-way projection system for presentation of and selection from repertories of selectable information said system comprising:

a projection surface;

means for projecting a repertory of selectable information on said projection surface in predetermine alignment; a light reflector for placement at selected positions on said projection surface to reflect light provided by said projecting means from the selected positions on said projection surface associated with selectable information; and

means responsiveto light from said light reflector emanating by reflection'from said projection surface for detecting the relative position of said selected position on said projection surface thereby to provide an indication of the location on said projected image of said selected position;

said projection surface including means for providing a visible display of said selectable information in the projected repertory for viewing and for transmitting a portion of the light projected onto said surface and reflected by said light reflector at said selected position for reradiation toward said-detecting means in amagnitude substantially greater than other light emanating from said surface.

2. The two-way projection system of claim 1 wherein 6 said detecting means further includes:

v an array of photosensitive detectors;

means for imaginglight from 'said selected position onto said photosensitive detector array with predeterrnined alignment between each detector in the array and predetermined positions of said selected position on said projection surface; and

means for sampling thephotosensitive detectors in said array to determine which of said detectors is receiving illumination from said light reflector at a selected position.

3. The two-way system of claim 2 wherein:

said imaging means includes means for producing on said detector array a generally focused image of said projection surface;

said detector array includes a two dimensional matrix of said photosensitive detectors; and

said sampling means includes means for scanning the rows and columns of said matrix of detectors to provide a digital indication of the position of a detector illuminated by light from said light reflector at said selected position. p I

4. The two-way projection system of claim 3 wherein said scanning means further includes:

means for providing a plurality of scans of said detector array and corresponding indications of the position of an illuminated detector;

means for determining that the indicated detector during adjacent scans remains the same for a predetermined number of adjacent scans to provide a verified detector indication; and

means responsive to the verified detector indication for providingan output representation of the corresponding detector after said predetermined number of adjacent scans.

5. The two-way projection system of claim 2 wherein said imaging means includes a mask with apertures therethrough in a two dimensional arrangement providing a pattern of light on said detector array in'response to light emanating'from a selected position on said projection surface; and said detector array includes a two dimensional arrangement of detectors positioned for selective illumination by'said pattern of light. 6. The two-way projection system of claim 1 wherein said projecting means further includes:

a projector containing a plurality of selectable information r'epertories for projection; means for advancing said projector from one selectable repertory for projection to a different selectable repertory for projection; and means for providing an' output indication of the repertory projected from said plurality of selectable reper'tories. I 7. The two-way projection system of claim 1 wherein said projection surface further includes:

a light diffusing coating; and a plurality of apertures through said light diffusing coating at predetermined points thereby to more readily transmit light from said light director for radiation to said detecting means when said selected position coincides with one of said apertures. 8. The two-way projection system of claim 1 wherein said projection surface includes a Fresnel lens.

9. The two-way projection system of claim 1 further including:

abeam-s plitter; in the path of and transmissive to light from said projecting means to said projection surface; v I said beam-splitter. responding to light emanating from said projection surface to redirect the emanating light; and

means for imaging the redirected light on said detecting means. 7 I 10. The two-way projection system of claim 9 wherein said light reflector includes a retro-reflector.

11. Atwo-way projection system for an inputtermi nal and providing for the display of a repertory of sesaidrepertory including a plurality of information selections and selection points projected in alignment with said predetermined portions;

light director means for providing a rear emanation of light from said surface at one of said predetermined portions;

a two-dimensional array of light sensitive detectors arranged in a row and column pattern; 4

means for forming on said array a light pattern in responseto light emanating from said one of said predetermined portions of said projection surface, said pattern activating one or more detectors;

a counter cycling through a predetermined total count with each count state designating a row and column combination;

means responsive to the count cycling of said counter for scanning said array of detectors to provide a first signal when the row and column combination designated by the count state identifies an activated detector; means for storing the count state corresponding to 10 said first signal; means for comparing the stored count state for a prior first signal with the current count state of said counter to provide a second signal in response to identity in the count states compared; means for counting sequential second signals coincident with said first signal toward a predetermined total count; means for reinitiating the counting of said counting means prior to its predetermined total count in re sponse to one of said first and said second signals without the other; and means responsive to the predetermined total count of said counting means for providing an output indication to indicate that the stored count state represents input information. 1 12. The two way projection system of claim 11 further including:

means responsive to said output indication, said second signal and the absence of said first signal for counting toward a further predetermined total count; and means responsive to said further predetermined total count for removing said output indication. 13. The two-way projection system of claim 11 wherein:

said projection surface includes translucent portions for forming an image and transparent portions; said projection means includes a random access pro jector for transparencies containing said repertories and means for selecting a transparency for proand a single column of detectors.

Claims

1. A two-way projection system for presentation of and selection from repertories of selectable information said system comprising: a projection surface; means for projecting a repertory of selectable information on said projection surface in predetermined alignment; a light reflector for placement at selected positions on said projection surface to reflect light provided by said projecting means from the selected positions on said projection surface associated with selectable information; and means responsive to light from said light reflector emanating by reflection from said projection surface for detecting the relative position of said selected position on said projEction surface thereby to provide an indication of the location on said projected image of said selected position; said projection surface including means for providing a visible display of said selectable information in the projected repertory for viewing and for transmitting a portion of the light projected onto said surface and reflected by said light reflector at said selected position for reradiation toward said detecting means in a magnitude substantially greater than other light emanating from said surface.

2. The two-way projection system of claim 1 wherein said detecting means further includes: an array of photosensitive detectors; means for imaging light from said selected position onto said photosensitive detector array with predetermined alignment between each detector in the array and predetermined positions of said selected position on said projection surface; and means for sampling the photosensitive detectors in said array to determine which of said detectors is receiving illumination from said light reflector at a selected position.

3. The two-way system of claim 2 wherein: said imaging means includes means for producing on said detector array a generally focused image of said projection surface; said detector array includes a two dimensional matrix of said photosensitive detectors; and said sampling means includes means for scanning the rows and columns of said matrix of detectors to provide a digital indication of the position of a detector illuminated by light from said light reflector at said selected position.

4. The two-way projection system of claim 3 wherein said scanning means further includes: means for providing a plurality of scans of said detector array and corresponding indications of the position of an illuminated detector; means for determining that the indicated detector during adjacent scans remains the same for a predetermined number of adjacent scans to provide a verified detector indication; and means responsive to the verified detector indication for providing an output representation of the corresponding detector after said predetermined number of adjacent scans.

5. The two-way projection system of claim 2 wherein said imaging means includes a mask with apertures therethrough in a two dimensional arrangement providing a pattern of light on said detector array in response to light emanating from a selected position on said projection surface; and said detector array includes a two dimensional arrangement of detectors positioned for selective illumination by said pattern of light.

6. The two-way projection system of claim 1 wherein said projecting means further includes: a projector containing a plurality of selectable information repertories for projection; means for advancing said projector from one selectable repertory for projection to a different selectable repertory for projection; and means for providing an output indication of the repertory projected from said plurality of selectable repertories.

7. The two-way projection system of claim 1 wherein said projection surface further includes: a light diffusing coating; and a plurality of apertures through said light diffusing coating at predetermined points thereby to more readily transmit light from said light director for radiation to said detecting means when said selected position coincides with one of said apertures.

8. The two-way projection system of claim 1 wherein said projection surface includes a Fresnel lens.

9. The two-way projection system of claim 1 further including: a beam-splitter in the path of and transmissive to light from said projecting means to said projection surface; said beam-splitter responding to light emanating from said projection surface to redirect the emanating light; and means for imaging the redirected light on said detecting means.

10. The two-way projection system of claim 9 wherein said light reflector includes A retro-reflector.

11. A two-way projection system for an input terminal and providing for the display of a repertory of selectable input information and for the identification of selected input information, said system comprising: a projection surface formed to include a surface which provides a forwardly viewable image of a rear projected information repertory and to provide substantial transmission of light from front to rear for backward emanation of said light in at least a plurality of predetermined portions; means for rear projecting a repertory of selectable information for display on said surface; said repertory including a plurality of information selections and selection points projected in alignment with said predetermined portions; light director means for providing a rear emanation of light from said surface at one of said predetermined portions; a two-dimensional array of light sensitive detectors arranged in a row and column pattern; means for forming on said array a light pattern in response to light emanating from said one of said predetermined portions of said projection surface, said pattern activating one or more detectors; a counter cycling through a predetermined total count with each count state designating a row and column combination; means responsive to the count cycling of said counter for scanning said array of detectors to provide a first signal when the row and column combination designated by the count state identifies an activated detector; means for storing the count state corresponding to said first signal; means for comparing the stored count state for a prior first signal with the current count state of said counter to provide a second signal in response to identity in the count states compared; means for counting sequential second signals coincident with said first signal toward a predetermined total count; means for reinitiating the counting of said counting means prior to its predetermined total count in response to one of said first and said second signals without the other; and means responsive to the predetermined total count of said counting means for providing an output indication to indicate that the stored count state represents input information.

12. The two-way projection system of claim 11 further including: means responsive to said output indication, said second signal and the absence of said first signal for counting toward a further predetermined total count; and means responsive to said further predetermined total count for removing said output indication.

13. The two-way projection system of claim 11 wherein: said projection surface includes translucent portions for forming an image and transparent portions; said projection means includes a random access projector for transparencies containing said repertories and means for selecting a transparency for projection; said forming means including a lens; and said array is a generally rectangular arrangement of detectors.

14. The two-way projection system of claim 11 wherein: said forming means includes a mask having a pattern of angled light transmissive slits; and said detector array includes a single row of detectors and a single column of detectors.