US3188474A - Photosensitive electro-optical calculating machine - Google Patents

Description

`)une 8, 1965 T. l. REss 3,188,474

PHOTOSENSITIVE ELECTRO-OPTICAL CALCULA'IIING MACHINE Original Filed Jan. 24, 1956 Two I EIGHT f7 A Z4 3f j D E] L] [g1 El THOMAS I. RESS BY #AWN/m..

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nited States Patent imi 3,188,474 PHTOSENSlTl'l/E ELECTRO-OPTICAL CALCULATENG MACHENE Thomas l. Ress, Riverton, NJ., assigner to international This invention relates to a counting device, and particularly to an electro-optical device for operation in a binary sequence. The device disclosed herein is similar in certain respects to the electro optical counter disclosed in my copending application Serial No. 557,381, iiled I anuary 4, 1956.

This application is a division of my copending application Serial No. 560,938, tiled January 24, 1956, now Patent No. 2,985,763, issued May 23, 1961.

In an effort to improve and speed up the process of machine calculation, numerous techniques have been developed employing electronic and even electro-optical devices. These electronic calculating devices generally employ numerous components. As for the electro-optical calculating devices, they consist or" a light generating source whose beam transmission is logically controlled by deflecting elements before operating certain photoelectric cells. in these electro-optical arrangements, one photoelectric cell must be employed for each position of count- `ing and each such position cell must be externally activated. The large number of components and the rigidity of operation resulting from these prior electro-optical calculating techniques does not make for the most efcient type of operation. y

Therefore, it is the principal object of this invention to provide an eiiicient and economical electro-optical calculatin g device.

Another object is to provide such a calculating device in which light-responsive elements register a plurality of light pulses in codal form.

Another object is to provide an improved electro-optical counter.

According to this invention, the counter consists of a number of photoconductors and electro-luminescent spots all of which are electrically interconnected in a manner to register digit representing light pulses. Each counting position comprises a pair of input photoconductors that are activated by digit representing light pulses. One of these input photoconductors, upon activation, energizes an output phosphor spot which records and manifests the value represented by the light pulse. An electro-optical loop circuit formed by this input photoconductor and the output spot stores the value entered into the counter until the next light pulse arrives, or the counter is reset to Zero. The appearance of every second or even light pulse in a counting position activates the other input photoconductor, which serves to energize a carry phosphor spot for the purpose of transferring the value in the lower counting position to a higher counting position. The carry phosphor spot also brings about the de-energization of the output phosphor spot.

Other objects of the invention will be pointed out in the following description and claim and illustrated in the accompanying drawing, which disclose, by way of example, the principle of the invention and the best mode,

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sassari which has been contemplated, of applying that principle.

The single drawing is a schematic diagram showing an electro-optical counter according to the invention.

Generally, the invention consists of electrically and optically interconnected conventional photoconductors and electro-luminescent spots in the form of a binary counter. Such a counter is composed of basic electrooptical circuits. For example, the series connection of a photoconductor element and a phosphor spot permits the spot to be activated when the photoconductor receives oa light pulse. The series operation or" electro-luminescent and photoconductive material is described in Review of Scientiiic instruments (lune 1953) Vol. 24, No. 6 pages 471-472. ln the parallel connection of a photoconductor and phosphor spot, the appearance of a light. pulse on the photoconductor de-energizes or quenches the phosphor spot. Two photoconductors in series with a phosphor spot permit the spot to be activated only if both photoconductors receive light pulses. These interconnected components may be placed in printed circuit fashion on an insulated base of a limited dimension with a thin conductive strip between the components. The preferred arrangement is to print the photoconductors and electroluminescent spots closely together on both sides of a transparent plate such as glass. The disposition of phosphor material and photoconductor material on opposite sides of a transparent insulator for optical coupling purposes is described in Mellon Institute of Industrial Research, Quarterly Report No. 3 of the Computer Components Fellowship (First Series) April 1l, 1951 to July 11, 1951, Section VI, Optical Components for Digital Computers (pages Vl-9 and VI-lO). A conventional opaque masking plate may be used where a photoconductor must be shielded from adjacent light sources, that is, where feedback is not required.

The drawing illustrates the electrical and optical connections forming a four position binary counter. The solid lines between the components indicate electrical connection, and the` dotted lines represent optical connections. The squares represent photoconductors, and the circles represent electro-luminescent phosphor spots.

According to this invention, a suitable source of electrical energy 1l provides the necessary AC. power, for example, 600 volts, through reset switch 12, to all input photoconductors and all output phosphor spots. Reset witch 12 may be designed to operate manually or automatically. Cam 13, with its associated contacts 13a, serves to connect the energy source 1l to the carry spots in each binary order. The counter is thereby capable of recording light pulses and transferring this information between the binary positions, only when reset switch 12 and cam contacts 13a are closed.

As shown, each of the counting positions has two input photoconductors which are subjected to the light pulses to be counted. With regard to the binary-one position, input photoconductors 14 and 215 are subjected simultaneously to input light pulses which may be supplied, for example, by a Lucite tube of Y configuration whose stem portion receives the light pulses, and whose diverging branch portions are optically coupled to photoconductors 14 and 15, respectively, to communicate the received light pulses thereto. A Lucite tube of this sort is disclosed on p. 471 of the previously referred to (June 1953) issue of Review of Scientific instruments and, also, i

in my copending application Serial No. 557,381, tiled January 4, 1956. Input photoconductor 14 is directly connected to input phosphor spot 16 and photoconductor 17, and therefore, conducts current to both these components When a light pulse impinges on photoconductor 14. Photoconductor 15, on the other hand, conducts current to photoconductor 18 for energizing the latter after a light pulse impinges on photoconductor 15.

Photoconductors and 18 have dilferent light-response times to prevent both photoconductors from being energized simultaneously upon the application of the first and` every odd numbered light pulse. By this is meant that, as shown in FIG. 2, there is some delay between the time a light pulse is incident on both of photo-conductors 14 and 15 and the time the phosphor spot 16 is activated by the illuminated photoconductor 14 to cause light to be incident on photoconductor 18. Therefore, the photoconductor 18 responds to light at a time later than does the photoconductor 15. Since the input light pulses impinge on both inputphotoconductors 14 and 15 simultaneously, both conduct current to output spot 16 andphotoconductor 18, respectively. Thereupon, output spot 16 becomes energized, providing radiant energy for photoconductor 18. However, before photoconductor 184 can be fully activated by output spot 16, photoconductor 15 becomes de-activated as a result of the termination of the input light pulse. Only when the second and every even light pulse is applied willl both photoconductors be activated simultaneously.

Since photoconductors 15 and 1d are in series with carry spot 19, it is necessary that both these photoconductors be activated simultaneously if carry spot 19 is to be lighted. It is important that the input light pulse be of a duration which is sutlcient for input photoconductor 15- to bring series-connected photoconductor 18 into an active State before photoconductor 15 is returned to its inactive, state. That is to say, as photoconductor 18 reaches the point of being activated as a result of current provided by input photoconductor 15 and light beams transferred by output spot 16, input photoconductor 15 reaches the point of de-activation. Therefore, carry spot 1.9 is incapable of activation during the time that the rstl andv every odd numbered light pulse is being recordedY in the counter.

Output phosphor spot 16 develops a closed loop with input photoconductor 14, through an optical feedback arrangement, duringV the time that input conductor 14 receives al light pulse. Photoconductor 14 and electroluminescent spot 16 are assumed to be on opposite sides of a glass plate. After the light pulse has been terminated, the radiant energy fed back by spot 16 to photoconductor 14, serves to make this photoconductor conductive, and the electrical energy which photoconductor 14 makes available to output spot 16 generates further radi'antfenergy, in this way forming a closed loop. Spot 16 also maintains photoconductor 18 activated upon the termination of the first light pulse. As in the case of photoconductor 14, photoconductor 18 is assumed to be located on a glass plate opposite spot 16. Photoconductors14, and 18 may be on the same side opposite a larger spot 1,6I or onseparate plates opposite spot 16. Output spot15rwillcontinue to operate photoconductors 14 and 18 until output spot 16 is quenched or de-energized by the activation of its parallel connected photoconductor 17.

4They counter will now be described in terms of its ability tocount light pulses that are serially entered into the counter through the binary one position circuit. As

stated above, the entry of the first digit representing light pulse brings about the energization of output spot 16, which is then maintained in an energized state by the photoconductor 14.

' An explanation of the conjoint operation of photoconductor 14fand phosphor spot 16 is as follows: Ignoring, for the time being, the effect ofthe photoconductor 17, the photoconductor 14 and phosphor spot 16 are connected in series and, therefore, divide between them the A.C. voltage from source 11 in proportion to the relative impedance values of these elements. ln the absence of light incident on photoconductor 14, the impedance of the photoconductor 14, relative to that phosphor spot 16, is sufciently high to maintain the voltage across the spot below a value at which the spot will become and remain electro-luminescent. The impingement of the rst light pulse on photoconductor 14 reduces the impedance thereof to the extent of momentarily increasing the voltage across spot 16 to a point Where the spot becomes electro-luminescent. Thereafter, the light received by photoconductor 14 from spot 1,6-maintainslthe impedance of the photoconductor sufficiently reduced that. the voltage across the spot continues to excite the spot into electroluminescence.

The `second input pulse activates input photoconductors 14 and 15. Since photoconductor 14l is in. an activated state at this time, as a result of its feedback arrangement with spot 16, the activation of photoconductor 14 has no effect on the circuit at this time. However, the activation of photoconductor 15, at the same time that photoconductor 18` is activated by output spot. 16, illuminates carry spot 191. The energization of carry spot 19 then causes photoconductors 1'7 and. 2(3.to be activated. Inasmuch as photoconductor 17 receives radiantenergy from carry spot 19 and electrical energy from photoconductor 14, photoconductor 17 is activated to quench output spotl 16. Photoconductor Z6 maintains carry spot 192 illuminated until cram 13 opens contact 13a.

As an explanation of how spot :t9-becomes `and remains illuminated, .the photoconductors 15 and `18 in series and the photoconductor 29, in parallel with this series combination, together provide `a net photoconductive impedance which is in series 'with phosphor spot 1.9, and which is interposedibetween this phosphor spot 19 andthe source 11- of A.C. voltage. Thus the A.C. voltage from source 11v will ,be divided between this net photoconductive impedance and the `spot 19in proportion tothe relative impedance values thereof. The photoconductor` 20 initially is dark. So long as light is incident on neither photoconductor .115 or ,18, or incident on photoconductor `18 only,

the value of the net photoconductive impedance, relative'.

to that of spot 19, is sufficient to maintain the voltage across the spot below a Ivalue at :which the spot will become electro-luminescent. When however, photoconductor -18 is illuminated from spot 16 land when, at the same time, the second light pulse is incident eon photoconductor 15, the net photoconductive impedance is so reduced that the voltage across .spot 19 rises to a value where the spot ybecomes illuminated. When the spot 19 becomes illuminated, the light therefrom, which is incident on. photoconductor Ztl, reduces the impedance lof this last named photoconductor to maintain .the net photoconductive impedance at` a value where the voltage developed` across spot 19 continues to excite it into electro-lumines, cence even after `both of photoconductors y'15'rand 18 have lreturned to the dark state.

The quenching action of the photoconductor 1'7- is as follows. As previously explained, the series combination of photoconductor |14 `and phosphor .spot 16 provides a voltage dividing effect which, when photoconductor 14 receives light from spot `16, serves to maintain the voltage across `spot 16 at a value which continues to excite the spot into electro-luminescence. This previous explanation assumes that the photoconductor 117 is dark, and that the series combination `of elements 14 and 16 operates as previously described, despite the fact that, ibeoause photoconduct-or 17 is in parallel with spot 16, the combined dark impedance of photoconductor 17 andimpedance of spot 16 is a net effective impedancewhich is -in series with photoconductor i141, and iwhich is somewhat less than the impedance which would be -in series with this photoconductor if yonly the spot 16 ,were present.

Consider now what happens when photoconductor 1'7 receives light from phosphor spot 19. The ensuing re-` duction in impedance of photoconductor 17 reduces the combined impedance (of photoconductor .17 and spot 16) to a point where, due to the voltage dividing action provided by `this combined impedance and the impedance of photoconductor 114 when illuminated, the voltage across spot 16 no longer is able to `sustain the spot 16 in illuminated condi-tion. Under these circumstances the light output from spot `16 terminates to thereby cause the impedance of photoconductor 14 to -rise to its dark impedance value. As previously explained photoconductor 14, when at its dark impedance value, prevents spot |16 from becoming illuminated.

At the same time that carry spot 19 activates quenching photoconductor 117 for the purpose of tie-energizing output spot .16, carry spot 19 causes output spot 23 in the binary two position to be illuminated in the following manner. The illumination of car-ry spot .19 brings about a transfer of radiant energy to the binary two position input conductors Z1 .and 22. The activation of photoconductor 21 develops a current which illuminates -output spot 23. Soon after this spot is energized, it lfeeds back radiant energy to photoconductor 21, thereby developing .a closed loop dor storing a digit 2.

Photoconductor 22 is also activated by the radiant energy made available by carry spot 19. Before photoconductor 24 can be simultaneously activated by the radiant energy provided by output spot 23, photoconductor 22 is caused to be tie-activated. This is accomplished by the de-energization of carry spot 419 as a result of the opening of cam contacts 13a. The momentary cle-energization of carry spot 19 terminates the loop circuit formed by carry `spot 19 and photoconductor 20. Since radiant energy is not available for the short interval in which contacts 113:1 are open, photoconductor 20 is de-activated and unable to develop current for spot 19. The subsequent closure of cam -contacts 13a cannot re-energize this loop circuit, since photoconductor 2t) can only be activated by the simultaneous application of radiant and electrical energy. It should be clear that the operation of cam 13 must be synchronized with the input light pulses.

At the time that the third light pulse is entered into the binary one circuit, all the elements in the binary one circuit lare in .a rie-activated state. The cle-activated condition of -output spot 16 indicates an absence of a digit 1 value in the counter. Carry spot 19 is also de-activated lat this time, as explained above. Only input photoconductors Z1 and Z4 and output spot 23 in the binary two circuit are in an activated state. Output spot 23 continues to maintain input photoconductor 211 `and output photoconductor 24 in an activated state.

The appearance of a third light pulse in the binary one circuit activates photoconductors 14 and 15. The effect of this light pulse on the binary one circuit is similar to that in which the first light pulse had been entered. That is to say, output spot 16 is energized, forming a loop circuit with photoconductcr 14. `Carry spot 19 cannot be energized at this time. Therefore, at the end of .the third iight pulse, output spots 16 .and l23 are illuminated to indicate the absence of a digit 3. The opening of cam contacts `13a at the end of the third input pulse has no effect on the counter since carry spot `19 and all the other carry spots are in a tie-energized state.

The input of a fourth light pulse to the binary one circuit has an effect on this circuit identical to that 'already explained in the case of the second light pulse.

`That is to say, photoconductors and 18 are simultaneously activated to energize -carry spot 19, whose radiant energy activates photoconductor 17 and brings about fthe -de-energization of output spot 16. The radiant energy transferred from carry spot 19 to photocouductor 21 has no effect on the binary two circuit inasmuch as photoconductor 21 is already in an active state. However, the transfer of radiant energy from carry spot 19 to photoconductor 22 places photoconductors 22 and 24 simultaneously in an activated condition. The electrical energy which is now transferred from photoconductor Z4 to carry spot 25 puts this carry spot in an illuminated state. Carry spot 25 then transfers radiant energy to photoconductors 26, 27, 28 and 29. The activation of photoconductor 26 develops a loop circuit with carry spot 25 for the purpose of keeping carry spot 15 energized until cam contacts 13a are opened. The activation of photoconductor 27, which is parallel to output spot 23, causes photoconductor 27 to quench output spot 23.

The activation of photoconductor 28, on the other hand, by the radiant energy transferred from carry spot 25, causes output spot .3u of the binary four circuit to be illuminated, developing a loop circuit between photoconductor 28 and output spot 30. The transfer of radiant energy from carry spot 25 to photoconductor 29 has no effect on the binary four circuit, as previously explained with regard to the binary one and two circuits. After the entry of the fourth input light pulse, when cam contacts 13a are opened, output spot 3u alone is illuminated to indicate a digit 4 inthe counter.

The entry of subsequent light pulses in a counting sequence will in a similar fashion operate the electrooptical counter. That is to say, the entry of a fifth pulse into the binary one circuit will cause output spots 16 and 3i) to be illuminated. A sixth pulse Would cause output spot 16 to be rie-energized and output spots 23 and 3i) to be illuminated. Therentry of a seventh pulse would bring about the illumination of output spots 16, 23 and 311.

The entry of an eight light pulse causes output spots 16, Z3 and 3i) to be de-energized and output spot 37, which represents 8, to be energized in the following manner. The appearance of the eighth light pulse in the binary one circuit energizes photoconductors 15 and 18 simultaneously to illuminate carry spot 19, which activates photoconductcr 17 to quench spot 16. Carry spot 1@ also brings about the simultaneous activation of photoconductors 22 and 24 to illuminate spot 25'. The radiant energy from spot 25 then activates photoconductor 27 to quench spot 23. The radiant energy from carry spot 25 also brings about the simultaneous activation of photoconductors 29 and 31 for the purpose of illuminating carry spot 32. The radiant energy from carry spot 32, in turn, activates photoconductor 341, thereby bringing about the de-energization of output spot 3i). At the same time, the radiant energy transferred by carry spot 32 to photoconductor 35 illuminates output spot $7, which represents a value of 8 in the counter.

It may thus be clearly seen that the counter, according to this invention, may serve to count to any magnitude in the binary notation by the addition of other electro-optical circuits beyond the binary eight position. To reset the counter at the end of a selected sequence of entries, it is only necessary to open `switch 12, thereby cutting off the input photoconductors and the locking photoconductors associated with each carry spot from portier source 11.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will b-e understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. 1t is the intention, therefore, to be limi-ted only as indicated by the scope of the following claim.

I claim:

A two-stage, cyclical-ly operable electro-optical device adapted to have operating voltage applied thereto, and elements each adapted to become and remain illuminated comprising first and second solid state electro-luminescent only when the voltage across the element exceeds a predetermined value, dirs-t and second circuits adapted to control the voltages across said elements and comprised, respectively, of lrstf andv second solid state photoconductors which are. electrically coupled to said second and rstelements, respectively, and which are optically coupled to saidy first and second elements, respectively, to receive light therefrom, at least said second photoconductor being electrically in parallel with the. element to which the photoconductor is electrically coupled, and means adapted by at least applying successive input signals to said circuits to render` said circuits effective to produce oper-ation cycles for said device which are repetitive for every successive group of two successive signals, and in which, in any one cycle, said rst element References; Cited by the lbiamulnexfl UNITED srATEs PATENTS 12/55 Allen et al. 25,0--209r X 111/59- Kazan 25o- 72:13A

RALPH (l.V NILSQN, Primary Examiner. RICHARD WQOD, MAX L. LEVY, Eqicaminers.

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