US2013162A

US2013162A - Television

Info

Publication number: US2013162A
Application number: US705413A
Authority: US
Inventors: Harold J Mccreary
Original assignee: Associated Electric Laboratories Inc
Current assignee: Associated Electric Laboratories Inc
Priority date: 1924-04-10
Filing date: 1924-04-10
Publication date: 1935-09-03
Anticipated expiration: 1952-09-03

Description

SePf- 3, 1935. H. J. MCCREARY 2,013,162

TELEVI SION Filed April 10, 1924 5 Sheets-Sheet 1 Sept 3, 1935 H. J. MccREARY 2,013,162

TELEVI S ION Filed April 10. 1924 s sheets-sheet 2 Hij; A

I N V EN TOR. /drv/d J /Zf'realy A TT ORNEYS.

Sept 3, 1935. H. J. MccREARY 2,013,162

TELEVISION Filed April 10. 1924 3 Sheets-Sheet 5 A TTRNEYS.

Patented Sept. 3, 1935 TELEVISION Harold J. McCreary, Chicago, Ill., assignor, by

mesne assignments,

to Associated Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware 4ripplimmo'n `April 1o, 1924, serial No. 705,413

` 28 Claims.

Images of objects have heretofore been transmitted through distances and the present invention relates primarily to this art. In the prior methods or systems, soy far as I know, the object of which an image was to be transmitted was scanned by means of mirrors, shutters, or other movable mechanical devices. The primary object of the present invention is to produce a system of transmission of images which vdoes not depend upon movable mechanical elements of any kind excepting, of course, the movable members of generators which supply the necessary alternating currents.

In carrying out my invention, I scan the image at the sending station with a cathode ray and simultaneously scan a sensitive or responsive surface at the receiving station to reproduce the image. In one of its aspects, therefore, my invention may be regarded as having for its object to produce synchronous deflection of cathode rays at the sending and the receiving stations.

So far as I know, no prior system has transmitted images in the natural colors of the objects whose images are to be transmitted. Viewed in one of its aspects, my invention may be said to have for one of its objects to produce a simple and novel system of transmitting images in natural colors.

In carrying out my invention I form an optical image and analyze the image instead of the object itself during the act of transmitting. This is accomplished, specifically speaking, by projecting the image upon one side of a special photoelectric plate over the other side of which a cathode stream or a cathode ray is caused to trace a path covering every portion of the plate. Viewed in another of its aspects, my invention may be regarded as having for one of its objects to produce a simple and novel photo-electric plate.

Since the cathode ray should impinge directly on the photo-electric plate it is advisable that the latter be placed Within the tube or the wall of the tube in which the cathode ray is generated; and therefore viewed in another of its aspects, my invention may be said to have for one of its objects to produce a simple and novel tube including a photo-electric plate and means for producing a cathode ray and moving the same over such plate.

The various features of novelty whereby my invention is characterized will hereinafter be pointed out with particularity in the claims; but, for a full understanding of my invention and of its objects and advantages, reference may be had to the following detailed description taken in connection with the accompanying drawings, wherein:

Figure 1 is a diagram illustrating a simple adaptation of nur invention employing wires between the apparatus at the sending and receiving stations; Fig. 2 represents the symbol used for illustrating the photo-electric plate in the other figures; Figs. 3, 4 and 5 are respectively a section, a side elevation, and an end elevationv of a fragment of one form of photo-electric plate; Figs. 6, 7 and 8 are sections through fragments of three other forms of the photo-electric plate; Fig. 9 is a view similar to Fig. 1, illustrating a system for transmitting images in natural colors; Fig. 10 is a diagram of the apparatus at the sending station by means of which impulses or waves are sent through space, thus avoiding the use of wires between the receiving and sending stations; and Fig. 11 is a. diagram of the apparatus at the receiving station that receives the impulses or waves. v

Referring first to Figure 1 of the drawings, I represents an object of which an image is to be transmitted. There is first formed an image of this object, conveniently by means of a camera. 2 having instead of the usual photographic plate a special photo-electric plate 3 to be hereinafter described. This photo-electric plate preferably forms the end wall or is arranged in one end of a suitable tube 4, usually of glass, adapted to produce a cathode ray or stream. In the arrangement shown, there is in the end of the tube, opposite that at which the plate 3 is located, a thermionic filament that constitutes the cathode, and also an anode 6 arranged between the cathode and the photo-electric plate. Between the anode and the cathode is a disc 1 having a small aperture in the center. The sources of energy for producing the cathode ray or stream are represented as being batteries 8 and 9. The cathode ray or stream is represented by the dotted line I0 that normally strikes the photo-electric plate at about the center, extending at right angles to the plane of the plate. Means are provided for rapidly deflecting the cathode stream to cause it to play over the entire inner surface of the photo-electric plate. In the arrangement shown, this is accomplished electrostatically, although any other suitable expedient may be employed; II and I2 representing two sets of deector plates, each set comprising two parallel plates lying on opposite sides of the ray, the two sets being spaced apart from each other in the direction of the length of the tube and the plates of one set being disposed at right angles to the plates of the other set. When alternating current potentials of different frequencies are impressed on the plates I I and I2, these plates constitute means for defiecting the electron stream so that it will trace a path covering the entire inner surface of the photo-electric plate; the path followed by the ray across the plate being a Lissajous gure if the potentials applied are sine waves. In the arrangement shown, the two plates of set II are connected to the opposite terminals of a high frequency generator I3, while the plates I2 are similarly connected to a low frequency generator I4.

The terminals of the photo-electric plate are connected to the terminals of a battery I5 or other suitable source of current arranged in series with the primary of a transformer I6.

The photo-electric plate is so constructed that a conductive path, completing the circuit containing battery I5, is formed through the photoelectric plate from any point against which the cathode ray impinges to the corresponding point on the opposite side of the plate, namely that which is illuminated by the image; the conductance of this path varying with a characteristic of light, usually intensity and color. Consequently, assuming the system to be in operation, the conductance of the path through which the current from the battery I5 and the primary of the transformer I6 must flow is constantly varying according to the intensity or color of the light, or both, at various points in the image.

lI'he secondary of the transformer I6 is in series with a battery I1 and their combined potentials are impressed on an amplifier I8; I9 represents the plate battery arranged in the output circuit of the amplifier tube. Consequently, the energy in the circuit completed by the photoelectric plate is ampliiied and may be carried through conductors 20 and 2I to any remote point such as a receiving station.

At the receiving station is a receiving tube 22 having at one end a fluorescent screen or a photographic plate 23. This tube is otherwise similar to the tube 4, containing a thermionic filament 25, an anode 26, a centrally perforated disc 21, that is the means illustrated for varying the intensity of the cathode stream, and two sets of deflecting plates 28 and 2S, respectively. Batteries 30 and 3I corresponding to the batteries Il and 9, at the sending station, are connected to the tube to supply the energy for producing a cathode ray 32 adapted to impinge upon the screen or film 23. The secondary of a transformer 33 is connected between the filament 25 and the disc 21. The primary of the transformer is connected across the

lines

20 and 2|, coming from the sending station. Consequently, when the system is in operation, the intensity of the cathodevray 32 will vary with the fluctuations in the train of energy leading from the sending station, namely in accordancev with the characteristic of the light, such as its intensity or color,

It will thus'be seen that the screen orplateat Y vthe receiving station will be'illuminated in such a manner that theintensity o'flightat each point will bear al definite relation to the intensity and color of light vat the corresponding point in the image at the sending station. Themovements of the cathode rays are so rapid that the member 23 at `the receiving station, -ifit be a fluorescent screen, will present to the eye of the observer the appearance of being-illuminated by a sheet of lightvcovering its entire area, `but differing in 'intensity at different points sovas vto reproduce the image thatv is formed at the sending station,

If the member 23 be av sensitized photographic plate or film, it will be aifected'in the same way as though an image were thrown on the same in a camera.

In Figs. 3 to 8 there are illustrated a few simple forms of the photo-electric plate. Referring to Figs. 3 to 5, 36 represents a slab of insulating material through which extend, conveniently at right angles to the fiat, broad faces thereof, a large number of independent conductors 31. Embedded in the faces of the slab are what may be termed grids of conducting material, indicated respectively at 33 and 33; the elements of these grids extending past the corresponding ends of the conductors 31 but out of contact therewith, preferably so that each conductor lies between two grid elements. These grids form the terminals of the plate and it is to these terminals that the-battery I5 in Fig. 1 is connected. In order to complete the battery circuit a conductive path must be established between at least one of the conductors 31 and both of the grids. Any expedient may be resorted to in order to cause a conductive path to be formedl between one of the conductors 31 and the grid 33 when a cathode stream impinges on the plate at the end of such conductor on the proper side of the plate. If the materials employed in the construction of the plate are not such as to produce the ,necessary conductive paths between the conductors 31 and the grid 39 under the influence of the cathode stream or ray, the plate may be coated with or have adjacent thereto a medium that will properly respond to the cathode ray. Thus, for example, a coating of potassium hydride, selenium, etc., may be placed on that face of the plate exposed to the cathode ray. Since the purpose of 'the cathode ray is simply to analyze the plate into small sections, the conductance of the paths between the conductors 31 and the grid 33 is preferably the same at all points on the plate; but the conductive paths on the other side of the plates must vary I in conductance according to the Vchosen characteristic or characteristics of the light in accordance with which the current or train of energy to be transmitted is to be modulated. The ksimplest method is to coat that face on which the image is formed with potassium hydride, vselenium or other suitable material. The dotted lines 40 and 4I in Fig. 1 represent the photoelectric'media.

While the element referred to as a photo-electric plate may conveniently take the form of a single unit in the form of a plate, yet it will bc understood that thetwo areas to be exposed respectively to light and to the scanning cathode ray need not even be in proximity to each other. As long as these areas are connected by `conductors extending from points in one of them to corresponding points in the other, their relative positions are of no importance. So also, the grids 38 and 39 may be replaced by any suitable conductor elements which span the area to be illuminatcd,- as long as the light and the electrons can reach the conductors 31. In Figs. 6 and 8 I have, however, shown several other simple forms which a single plate may have.

In the arrangement shown in Fig. 6 the bars or elements of the grids, 42 and 43, as well as the ends of the conductors 31, are sharpened and project beyond the faces of the slab of insulating material.

In Fig. 7 the elements or bars of the grids 43 and 44 lie spaced apart from the faces of the slab in which the conductors 31 are embedded.

In Fig. 8 I have shown a combination of the arrangements depicted in Figs. 3 and 7; the grid 38 being embedded in the slab and the grid 43 lying outside of the slab.

When it is desired to transmit images in natural colors, a. plurality of images are made so as to produce at the sending station images bearing the same relation to each other as do the color plates in the manufacture of colored lithographs. These images are transmitted to and reproduced at the receiving station in their corresponding colors, and there they are superimposed upon each other and form an image or picture showing the subject in natural colors. The images at the sending station are made by cameras viewing the subject through suitable color lters. Each image is then transmitted to a receiving unit, in the manner heretofore explained, where it is made visible on a suitable uorescent screen in the same color as the image at the sending station. By means of projection cameras these last-formed images are then reproduced on a screen or a sensitized plate, and form* a composite whole. If the images are collected on a screen they disclose to the observer the object in its natural colors; if upon a sensitized plate, they act on the plate in the same manner as though the object were being photographed on the latter, so that when the plate is developed it will bear a picture that is an accurate representation of the object at the remote sending station.

In Fig. 9, I have illustrated a system of transmission in colors, images in three primary colors. red, blue, and yellow being formed, transmitted and superimposed on each other. A, B. and C represent three separate units such as that described in connection with the sending station in Fig. 1. The unit A may bear the same relation to the object I as does that in Fig. l. The tubes and camera of units B and C may be arranged, as shown, coaxial with each other and at right angles to the axis of unit A. Mirrors 50 and 5I are so placed that light from the object is reected into the cameras of units B and C respectively. Light from the object passes through filters 52, 53 and 54 in passing into the cameras of the three units A, B and C, respectively, so that the three images differ from each other in that each corresponds to only one of the three primary colors present in the object.

At the receiving station are three receiving units D, E and F respectively, each corresponding to the unit described in connection with the receiving station in Fig. l. A single pair of generators, I3 and I4 serve to bring about the deections of the six cathode rays in the six cathde tubes, but each unit at the receiving station must be connected to the corresponding unit at the sending station by an independent modulating line or train of energy as indicated at a, b, and c, respectively. The fluorescent screens 55, 56 and 51, associated respectively with the units D, E and F are made of such materials that when illuminated by the cathode rays each present an image of the same color to that of the corresponding image at the sending station. This screen 55 may be made of glass or other suitable material coated with a mixture consisting of one part of bismuth sulphate to one hundred parts of calcium oxide; screen 56 may be made of glass or other suitable material coated with a. mixture consisting of one part of antimony oxide to one hundred parts of calcium oxide; and screen 51 may be made of glass or other suitable material coated with a mixture consisting of one part of bismuth oxide and one hundred parts of calcium oxide; and will produce respectively red, yellow and blue images.

The tubes of the units D, E and F bear the same relation to eachother as do those of the corresponding units at the sending station. In order to bring together the several images at the receiving station and assemble them into a composite whole, cameras d, c and f are so. placed as to form images of the illuminated

screens

55, 56 and 51, respectively. AThe camera d may throw an image directly on a screen or sensitized plate or nlm H, while th images produced by the other two cameras are reflected upon the member H by means of mirrors 58 and 59, respectively; the three images being superimposed on each other and forming a composite image 60 in the natural colors of the object.

In Figs. 10 and 11 I have shown means for transmitting through space the necessary waves or impulses to control the apparatus at the receiving station, Fig. 10 being the sending station and Fig. 11 the receiving station.

Referring to Fig. 10, 62 and 63 represent the conductors connecting the battery I5 and the primary of transformer I6 to the photo-electric plate of a sending station unit such as shown in Fig. 1. The secondary of the transformer is connected into the grid circuit of an amplifier 64 corresponding to the ampliiier I8 in Fig. 1. In the output circuit of amplifier 64 is the primary of a transformer 65 whose secondary is arranged in a closed circuit in series with the secondaries of two transformers, 66 and 61, and the primary of a fourth transformer 68.

The primaries of the transformers, 66 and 61, are connected in series with the generators, I3 and I4, respectively, to the deecting plates in the thermionic tube. Therefore there are impressed on this closed circuit, just described, three different sets of impulses, namely the modulating impulses, and the impulses produced by the high frequency and low frequency generators. By means of the transformer 68 these three sets of impulses are impressed on the input side of an amplier 69 which amplies all of them. While I have shown only individual ampliers it will of course be understood that any desired degree of amplication may be had by the use of the proper number of tubes. 'I'he output of the amplifier or modulator tube 69 is impressed on the output of an oscillator tube or tubes through a choke coil 10; only a single oscillator tube, 1I, being shown. 'I'he choke coil 19 serves to prevent the output of the modulator tubes from owing through the plate potential source and being lost to the circuit. The frequency to be transmitted is determined by the inductance and capacity in the ground antennae circuit; 12 representing the antennae, 13 the ground connection therefor, 14 a variable inductance, and 15 a variable condenser. The inductance of the antenn circuit is varied by changing the tap from the plate circuit of the oscillator tube to the inductance coil 14, and the capacity is varied by manipulating the condenser 15. A connection is made between the filament battery 16 of the oscillator and the antenme circuit at a point between the inductance coil 14 and the variable condenser 15, the connection including a high resistance 11 and a fixed condenser 18 arranged in series with each other in the order named. A lead extends from a point in this connection between the resistance and the fixed condenser to the grid of the oscillator tube.

Energy of four different frequencies is therefore radiated from the sending station, namely the train of energy controlled by the photoelectric plate, the high and low frequency impulses of the two generators, and the energy of the carrier wave of high frequency. These must all be collected at the receiving station, be separated from each other and be caused to produce an image corresponding to that at the sending station.

'Ihe collecting, amplifying and distributing means at the receiving station are shown in Fig. 11. Referring to this figure, and 8| represent respectively the antennrand the ground connection therefor, there being arranged in series with each other between the same the primary of a high frequency transformer 82 and a variable condenser 83. The antenna is tuned to correspond to thecarrier frequency of the sending station and oscillates at the same frequency as that at the sending station, and therefore impresses on the circuit containing the secondary of the transformer 82 potential variations which correspond to those sent out at the sending or transmitting station in relative magnitude, phase relation and variation. 'I'he secondary of the transformer 82 is connectedV to the input side of an amplifier tube 84, in parallel with a variable condenser 85. The primary of a high frequency transformer 86 is connected in the output circuit of the amplifier. Any desired degree of amplification may be had, but I have shown only one more tube, 81, in addition to the tube 84; the secondary of the transformer 86 being connected to the input side of this second tube.

After the proper degree of amplification has been attained, the energy output of the amplifier system is impressed on a suitable filter adapted to separate the carrier frequency, the two de- 'flector frequencies, and the modulator current from each other. This may conveniently be accomplished by constructing a filter such that it will pass given bands of frequency, one frequency after another being diverted as the range of frequencies that will pass successive stages if the filter is narrowed. After a useful frequency has been separated from the others -it may be amplified, if desired, and then be caused to do its intended work.

in the output circuit of the amplifier tube s1 is a choke coil or inductance 88 that prevents the passage of the carrier frequency, the latter being by-passed through a condenser 89 and being then eliminated. The remaining frequencies then reach a second inductance 90 which prevents the passage of the high-frequency deflecting current, the latter being by-passed through the primary of a transformer 9| from the terminals of ywhose secondary conductors 92 and 93 lead to one of the sets of deiiectin'g plates in the cathode ray tube at the receiving station. The two remaining frequencies pass through the inductance 90 and, when they reach anl inductance 94, the modulating frequency continues through the same but the low-frequency deiiector current is by-passed through the primary of a transformer 95 whose output is impressed upon the second set of deector plates at the receiving station through conductors 96 and 91. Condensers numbered consecutively 98 to |83 are connected in the output circuit of the amplifier 81, as

, shown, to control the paths of the useful potentials and cause the latter to' travel to the deing means or as oscillating means are provided' 10 with the necessary batteries which are illustrated but which, because there is nothing novel therein or' in their connections, are not described in detail.

4For the sake of clearness and brevity I have illustrated only a few simple embodiments of my invention and the several features thereof and have described them with particularity; but it will of course be understood that my invention is not limited to the specic forms of my invention thus illustrated and described, as I intend to cover all forms, methods and arrangements that come within the definitions of my invention constituting the appended claims. i

I claim:

1. The method of transmitting and receiving vision in colors which consists in forming a plurality of optical images corresponding to dinerent colors in the subject, causing all of a plurality of small sections of each image to produce photo-electric effects simultaneously, utilizing the photo-electric effects produced in the sections of each image successively to cause a characteristc of an electric current to be varied according to a characteristic of the light in the individual sections of the corresponding image, employing said currents in the production of pictures at a receiving station,I forming images of said pictures, and superimposing said images upon each other.

2. The method of transmitting and receiving vision in colors which consists in forming a plurality of optical images of the subject by photographing the subject through filters which cause to be produced images corresponding t0 a plurality of primary colors in the subject, causing all portions' of each image to fall simultaneously upon a photo-electric medium individual to such image, utilizing the photo-electric mediums to cause a characteristic in each of as many electric currents as there are images to be varied according to the intensity of light in the individual sections of the corresponding images, employing said currents in the production of pictures at a receiving station, and super-imposing said pictures upon each other.

3. In a television transmitter, a plate of insulating material, a plurality of minute pins or wires imbedded in said plate and connecting opposite sides thereof, means for producing an image on one side of said plate, photo-electric material on the image side of said plate for join- 1 dividuai areas on the image side of said plate to the vicinity of said ray, a circuit, and means for causing said ray to connect said conductors in said circuit successively.

5. In a system of television, means for producing an image, a plurality of insulated conductors, each having one end lying in the plane of said image, a circuit, light sensitive material for connecting the said lends of said conductors to one terminal of said circuit, means for producing a cathode ray, and means including said cathode ray for connecting the other ends of said conductors to the other terminal of said circuit one at a time.

6. In a television transmitter, a screen on which an image may be formed, a circuit which includes a plurality of parallel branches extending through said screen, said branches including gaps for space currents on the rear side oi' said screen but not on the image side thereof, a section of light sensitive material included in each branch on the image side of said plate, means for producing a cathode ray, and means including said cathode ray for rendering said gaps successively conductive.

7. In a television transmitter, means for producing a cathode ray, a plate located in the path oi said ray, a conductive body located adjacent said plate but spaced away therefrom on the cathode ray side, a circuit including the said body and Y a plurality of co-existing conductive paths extending through said plate, means insulating each said path from the others, and means for causing said ray to explore the plate to complete said circuit through cach of said paths in succession by space discharge between the plate and said body.

8. In a television transmitter, a plate composed of material sufficiently strong and thick so that the plate is self-supporting, means for forming an image on one side thereof, photo-electric material on the image side of said plate, a screen or grid on the other side, means for producing a cathode ray and for causing the same to scan said plate through the openings in said screen, and a circuit which is completed between the said screen and successive sections of said plate by said ray.

9. In a system of television, a plate on which an image may be produced, means for establishing a plurality of conductive paths extending between the faces of said plate, a circuit including said paths and including also two gaps for space discharge currents, one at each face of said plate, photo-electrical material for causing current to iiow across one gap under the action of light, and means for producing a cathode ray, which causes current to flow across the other gap by way of said conductive paths one at a time.

10. In a television transmitter, a cathode ray tube including means for producing a cathode ray, a, photo-electric plate impervious to the ray located in the pathl thereof, said plate including different materials one sensitive to light and the other not, the material insensitive to light being thick enough to bar passage of the cathode ray and the light sensitive material being conned to a coating on the plate, means for causing said ray to scan the plate, a circuit, and means including said plate and ray for producing a current flow in said circuit which varies in accordance with the amount of light reaching successive small areas of said plate.

11. In a television transmitter, means for producing a cathode ray, said means including a heated cathode, an anode, a source of current for heating said cathode, and a source of potential for establishing a potential diierence between the vcathode and anode, a plate impervious to the ray located in the path thereof, said plate including material insensitive to light and thick enough to bar passage of the ray, means for producing a scanning movement of the ray, light sensitive material deposited on said plate, means for forming an image on said material, a circuit for television currents, and means including said light sensitive material and the plate and eilectively responsive to the scanning operation by said ray to vary a characteristic of the current in said circuit in accordance with the light values in successive sections of said image.

12. In a television transmitter, a plate, means for forming an image on the front side of said plate, a circuit including a current source and extending to terminals on opposite sides of said plate, a solid light sensitive material joining the iront material to the plate at a plurality of points lying in the image plane, means for producing a cathode ray, and means for causing said cathode ray to scan the rear of the plate for establishing conduction between such points and the rear terminal oi' said circuit.

13. In a television transmitter, a circuit including a source oi' current and having a plurality of parallel branches, a series of breaks in said branches, said breaks all lying in an image plane, light sensitive resistance varying material connecting the two sides of each break, a second series of breaks in said branches, means for producing a cathode ray, and means including said cathode ray for closing the breaks of said second series successively.

14. In a television transmitter, a plurality oi closely compacted parallel conductor paths, said paths being present simultaneously, a minute section of selenium or similar resistance varying material included in each path, said sections all 1ocatedin an image plane, a circuit including a source of current, means for producing a cathode ray, and means including said cathode ray for connecting said paths successively in said circuit.

15. In a television transmitter, a plate on which an image can be formed, a plurality oi' insulated conductors connecting the two faces of said plate, a circuit having a terminal member on the image i'ace of said plate, a solid conductive connection between said terminal member and said conductors, said connection consisting of light sensitive material, means for producing a cathode ray, and means including said cathode ray acting on the rear face of said plate for completing said circuit over each of said conductors in turn.

16. In a television transmitter, means for producing an image, a circuit having a plurality of branches which extend through the plane of said image, said circuit and its branches being composed throughout of solid conductive material, a section of light sensitive resistance varying material included in each branch where it intersects the image plane, means for producing a cathode ray, and means including said cathode ray for changing the resistance of said branches successively.

17. In a television transmitter, a plate, means for forming an image on the face of said plate, a circuit including a plurality of parallel branches extending through the plate, each branch inclu ing metallic portions which are connected only by a light sensitive resistance varying material, means for producing a cathode ray, and means including said cathode ray acting on the rear face of said plate for closing said branch circuits successively.

18. In a television transmitter, a plate, light sensitive resistance varying material on the front side of said plate, a screen or grid on the same side of said plate in contact with said material, means for forming an image on the frontside of said plate, a circuit including said screen and having a plurality of branches extending through the plate, each branch including a portion of said light sensitive material, means for producing a cathode ray, and means including said cathode ray acting on the rear of said plate for rendering said branches successively conductive.

19. In a television receiver, a plurality of cathode ray tubes, a fluorescent screen in each tube which is scanned by the ray, each screen containing uorescent material which gives off a diilerent color of light, means for modulating each ray to produce a partial image on its associated screen, and means for combining said images to form a single picture in colors.

20. In a television receiver, a plurality of iiuorescent screens, each adapted to give off light of a different primary color, means for scanning each screen by a cathode ray, means for varying the intensity of each ray, in accordance with the amount of different primary color which is found at successive points on a distant object, thereby forming partial images of said object, each in a different color, and means for combining said images so as to form a single image in colors.

21. A television system comprising means for forming two partial optical images of an object, each from a different point of view, means including two photo-electric plates on. which said images are formed for determining the light values in successive small sections of said` images and for converting varying light values into variations in two currents of electricity, means for utilizing said currents in the reproduction of said optical images, and means for superimposing the reproduced images on one another to form a single picture.

22. In a television transmitter of the cathode ray type, a plate composed of material insensitive to light and thick enough so that it is self-supporting andr incapable of penetration by the cathode ray, means for producing an image on said plate, light sensitive material on the image side of the plate, a. circuit including a conductive member spanning the other side of said plate, means for producing a cathode ray, means for causing said ray to scan said plate, and means including said ray and plate for causing successive small portions of said material to control said circuit.

23. In' a television transmitter, a plate composed of insulating material, means for producing an image on said plate, light sensitive material on the image side of said plate, a conductive'member spanning the other side of said plate and supported thereon, means for producing a cathode ray and for causing it to scan said plate, the said plate being thick enough so that it is impervious to the ray at all points within its working area, a circuit including the said conductive member and said material, and means including the ray and plate for causing current variations in said circuit in accordance with the amount of light reaching successive small areas of the plate surface on which the said material is supported.

24. In a television transmitter, means for producing a cathode ray, an insulating plate located in the path of the ray, said plate being thick enough to be incapable of penetration by said ray and being composed of material whose insulating qualities are not affected by the ray, means for causing said ray to scan the plate, light sensitive material on one side of said plate, a separate conductive member spanning the other sido of said plate, means for focusing an image on said light sensitive material, a circuit including said conductive member, and means including said ray and plate for causing current variations in said circuit in accordance with the light reaching successive small sections of said material.

25. In a television transmitter using a cathode ray, a plate composed of material insensitive to light and thick enough so as to be incapable of 'penetration by the cathode ray, means for producing an image on said plate, light sensitive material on the image side of said plate, an element for collecting electrons emitted by said material, a conductive member spanning the other side of said plate, a circuit including the said conductive member, a source of currentand the saidcollecting element, means for producing a cathode ray, means for causing said ray to scan the plate, means including said ray and plate for causing successive small portions of said material to control said circuit, an amplifying tube, and means for coupling the grid of said tube to said circuit at a point between the said conductive member and the said current source.

26. In a television transmitter, a cathode ray tube including means for producing a cathode ray, a plate positioned in said tube in the path of the said ray, said plate being thick enough to beV impervious to the said ray, a coating of light sensitive material deposited onsaid plate, means for focusing an image on said material, a conducting member on the opposite side of said plate from the said ray and which the said ray is prevented from contacting because of the interposition of the said plate, a circuit including the said conducting member and said material, and means including said ray and plate for causing successive sections of said material to vary a characteristic of the current in said circuit.

27. In combination, a cathode ray tube including means for producing a cathode ray, an amplitying tube, a plate positioned in said cathode ray tube in the path of the said ray, said plate being composed of material preventing passage of the said ray through the plate, a coating of photoelectric material on said plate, a metallic conducting member on said plate in contact therewith and insulated from the said ray by the plate, a

circuit including said member, and means for coupling said circuit tothe grid of said amplifying tube.

28. In a television transmitter, a cathode ray tube including means for producing a cathode ray, an amplifying tube, a plate supported in and a gap for space currents between the plater and the said second member, and means for coupling said circuit to the tube.

HAROLD J. MCCREARY.

grid of said amplifying-