US2141059A - Television system - Google Patents

Description

Dec. 20, 1938. v. K. ZWORYKIN 2,141,059

TELEVISION SYSTEM F led Dec. 29, 1925 3 Sheets-Sheet l i INVENTOR 7 Vladimir K. Zwarykin. '7

W H014, I ATTORNEY WITNESSES:

20, 1938. v. K. ZWORYKIN 2,141,959

TELEVIS ION SYSTEM Filed Dec, 29, 1923 3 Sheets-Sheet 2 i Q 1 R WITNESSES: INVENTOR Vlqdumg; K. Zworyhm.

Dec. 20, 1938. V.K. ZWORYKIN 2,141,059

TELEVISION SYSTEM F l c- 29, 1923 3 Shets-Sheet 3 III' 0 WITNESSES:

INVENTOR Vladimir K. ZworyKin.

W u/ BY ATTORN EY Patented Dec. .20, 1938 FFEC TELEVISION SYSTEM Pennsylvania Application December 29, 1923. Serial No. 683,337

'40 Claims.

My invention relates, in general, to television systems.

One of the objects of my invention is to provide a system for enabling a person to see distant moving objects or views by radio.

Another object of my invention is to eliminate synchronizing devices heretofore employed in television systems.

Still another object of my invention is to provide a system for broadcasting, from a central point, moving pictures, scenes from plays, or similar entertainments.

The above and other objects of my invention will be explained more fully hereinafter with reference to the accompanying drawings forming a part of this specification.

Referring now to the drawings,

Figure l is a diagram of a station for broadcasting motion pictures or other visual indications, and may be considered the television transmitter.

Fig. 2 is a diagram of a receiving station for receiving the scenes broadcasted from the transmitting station.

Fig. 3 is a fragmentary view of an alternative arrangement for the transmitting station.

Fig. 4 shows an arrangement whereby the control of the transmitting and the receiving stations may be exercised from a central station; and

Fig. 5 shows the circuits of the transmitting station when a central station is used.

Both of these stations are shown by means of conventional circuit and apparatus diagrams in sufficient detail to enable the invention to be read- 35' ily explained and understood.

Any visual indications may be broadcasted by the transmitting set 5 consisting of apparatus and circuits and be received by the receiving set 2 consist ng of apparatus and circuits.

The apparatus of the transmitting set i comprises an antenna system 3 which is so tuned that it may oscillate at two separate and distinct frequencies. The oscillating circuit including the antenna 3 is connected on one side by means of a 45 transformer i to the plate circuit of an amplifier triode 5. The grid of the amplifier 5 is connected through a transformer 6 to the plate circuits of modulator triodes l and 8. An oscillator triode 9 0 is connected through a transformer ID to the grid circuit of the modulator triodes I and 8. The

above arrangement comprises what is known as an ordinary push-and-pull transmitting arrangement.

55 By means of a transformer H, the plate th cult of an amplifier i2 is also connected to the grid circuits of the modulator triodes. 1 and 8.

The oscillating circuit comprising the antenna 3 is also connected, by means of a transformer l3, to the plate circuit of an amplifier triode It. The 5 grid circuit of the amplifier I4 is connected, by means of a transformer I5, to the plate circuits of modulator triodes l6 and H. An oscillator triode I8 is connected, by means of a transformer is, to the grid circuits of the modulator triodes 10 I6 and Ill. By means of transformers 20 and 2|, alternating-current generators 22 and 23 are also connected to the grid circuits of the modulator triodes l6 and H.

The generator 22 is so constructed as to gen- 15 erate high-frequency alternating current of a frequency of about 1000 cycles, while the alternating-current generator 23 is adapted to generate an alternating current of a frequency at about 16 cycles.

It is, of course, obvious that triodes connected in oscillating circuits may be used in place of the alternating-current generators 22 and 23.

The plates 25 and 26 in a cathode-ray tube 21 are connected in the circuit through a series 25 transformer 24. Coils 28 and 29 are associated with the cathode-ray tube 27 in such position that the magnetic field which may be produced by said coils is parallel to the electrostatic field which may be generated by the plates 25 and 25, and 80 these coils are connected in circuit with the alternating-current generator 23.

The cathode-ray tube 21 is similar in some respects to the ordinary cathode-ray oscillograph and has a hot cathode 29, a diaphragm 30 and tubular anode 3i. The diaphragm 30 has a small hole so cut therein as to form the cathode ray into a thin beam.

In place of the ordinary fluorescent screen is substituted a composite plate 32 having layers of 40 different material. If the tube 21 has the usual low pressure gas, such as argon, the gas pressure will be substantially equal on the two sides of the plate 32. This is because the plate 32 is permeable to gas. It comprises a sheet 34 of aluminum foil on the face next the cathode ray. The foil must be thin enough to be readily penetrated by the cathode ray. It is as thin as it can be and satisfactorily support a layer 35 of aluminum oxide. The layer of aluminum oxide is as thin as it can be and still insulate a layer 36 of photoelectric material from the aluminum foil. The combined thickness of the whole plate 32 need not exceed one half mil.

Preferably the photoelectric material is potassium hydride, deposited in such a manner that it is in the form of small globules, each separated from its neighbor and insulated therefrom by the aluminum oxide. V

A lens 31 or system of lenses is secured in place by means of a frame 38 disposed at the end of the cathode-ray tube. The lens 31 is arranged to focus the image or scene to be observed upon the photoelectric material of the composite plate 32. A grid 39 is placed at some distance in front of the composite plate 32 and is connected to the grid of the amplifier triode I2. A high potential is applied to the anode 3| by a rectifier 40 which is supplied with current from an alternating-current source M.

' In the receiving device 2, an oscillating circuit 50, including an antenna 5I-;--is adapted to be resonant to current of two distinct frequencies, these frequencies being the frequencies generated by the oscillating circuits that include the triodes 9 and I8 of the transmitting set. An amplifier triode 53 is connected to the oscillating circuit 59. The plate circuit of the amplifier triode 53 is connected to a grid 54 in a cathode-ray tube 55.

The cathode-ray tube 55 is constructed in a manner similar to the ordinary cathode-ray oscillograph and comprises a hot cathode 56, the grid 54, a tubular anode 51, plates 58 and 59 that are used to set up an electrostatic field and a fluorescent screen 60. The anode 51 of the cathode-ray tube 55 is supplied with high voltage by the operation of a rectifier 6|, that rectifies the alternating current supplied by a source of alternating current 62.

The oscillating circuit 50 is also connected by means of a transformer 63 with a circuit 64. The circuit 64 is, in turn, connected by means of transformers 65 and 66 with the grid circuit of the amplifier triodes 61 and 68. The plate circuit of the amplifier triode 61 is connected with the plates 58 and 59 of the cathode-ray tube 55, while the circuit of the amplifier triode 68 is connected to the coils 69 and III that are associated with the cathode-ray tube 55 and so disposed with respect thereto that the magnetic fields generated by the coils are parallel to theelectrostatic field generated by the plates 58 and 59.

The transformer 65 is so constructed that it acts as a wave trap for the particular high fre-- quency that is generated by the generator 22 at the transmitting station so as to eliminate this frequency from the circuit 64. In a like manner, the transformer 66 acts as a wave trap for the particular frequency generated by the generator 23 by the transmitting station.

The alternative arrangement of the apparatus in the transmitting station, shown in Fig. 3, is adapted to transmit pictures. This system differs from the one shown in Fig. 1 in that an ordinary cathode-ray oscillograph is employed. One end only of the oscillograph has been shown. This oscillograph has the usual fluorescent screen I5. There is a photoelectric cell 16 situated close to the oscillograph. A lens 11 is disposed between the photoelectric cell and the cathode-ray tube arranged to focus the light from the fluorescent screen on the cell. A diapositive or ordinary photographic negative 18, that has the image on it that it is desired to transmit, is placed between the lens and the cathode-ray tube. The circuit connections of this arrangement are similar to those shown in Fig. 1.

The apparatus shown in Fig. 4 is practically identical with the apparatus shown at the right in Fig. 1, with the exception that there is provided a separate'antenna I03 and includes means whereby the synchronizing frequencies generated by the generators I22 and I23 may be radiated from .a central station.

Fig. 5 is very similar to Fig. 1, with the exception that the coils I09 and III! for creating the electromagnetic field for controlling the cathode beam and the plates III and H2 for creating the electrostatic field are controlled by detector triodes I01 and I09 which are connected to the receiving antenna through the oscillatory circuit IIII.

Having briefly described the apparatus shown in the drawings, I will now explainits detailed operation. For this purpose, it will be assumed that it is desired to broadcast the image of some object which is in front of the lens 31 associated with the transmitting cathode ray tube 21.

Ordinarily, the oscillations generated by the oscillator 9 are not radiated by the antenna 3. This is because of the fact that these oscillations are neutralized by the action of the modulator triodes 'I and 8, and, consequently, there is no transfer of energy into the secondary of transformer 6. The only manner in which the antenna can be set in oscillation by the operation of the triode 9 is by a change in condition in the primary of the transformer II which is connected to the grid 39 and to the aluminum foil 34 of the composite plate 32.

The light from the image placed before the lens 31 is so varied that, upon the focusing of this light upon the photoelectric globules 36 of the composite plate 32, electron emission of varying intensity by these particles takes place in accordance with the light from the object placed before the lens 31. This electron emission may be cons dered a species of conduction between the photoelectric globules 36 and the grid 39. This phenomenon is intensified by the argon vapor that fills the container 33 as a result of the ionization of the vapor.

In view of the factthat the aluminum oxide plate 35 is an insulator, there is no connection existing between the grid 39 and the aluminum plate 34, even though the photoelectric globules emit electrons. When the cathode beam strikes a particular point upon the aluminum foil, it is of sufiicient intensity to penetrate it, as well as the aluminum oxide. The action of the cathode ray on the aluminum oxide in its path, particularly in the presence of the gas, is to produce a conductive connection between the aluminum plate 34 and the particular globule or globules of potassium hydride in the path of the cathode ray. The electrons emitted by these globules are therefore subjected to the field produced by the battery 42 acting across the conductive part of the aluminum oxide. The amount of the emission will depend upon the degree of illumination of these globules. The current flowing in the circuit is dependent upon the electron emission from the globule or globules covered by the cathode beam. This current is amplified by means of the amplifier triode I 2. The current from, the grid 39 to the grid of the tube I2 is so small that no grid leakis necessary for the tube I2 although one may be supplied if desired. The output of the amplifier I2 now causes the modulator triodes I and 8 to'transmit, through the transformer 6, the high-frequency oscillations, generated by the oscillator triode 9, modulated in accordance with the current in the amplifier triode I2 which, in turn, is governed by the intensity of the light focused upon the particular spot at which the rent generators 22 and 23 are producing alternating current of a high and low frequency, respectively. By the operation of the modulator triodes l6 and H, the oscillations produced by the oscillator triode l8 are modulated in accordance with both the frequency of the alternatingcurrent generated by the generator 22 and the alternating current generated by the generator 23. This modulated high frequency current is amplified by the amplifier triode l4 and radiated by the antenna 3.

As the output of the alternating-current generator 22 is also connected to the plates 25 and 26 in the cathode-ray tube 21, an electrostatic field is set up by these plates which varies in accordance with the frequency of the current generated by the generator 22. As this electrostatic field varies, the electrostatic action upon the electrode beam causes it to be swung from one edge of the composite plate 32 to the other.

A portion of the alternating current generated by the generator 23 also traverses the coils 28 and 28 which, as before mentioned, are so positioned with respect to the cathode tube 21 that the magnetic field generated by these "coils is parallel to the electrostatic field generated by plates 25 and 26. The varying magnetic field set up by these coils tends to cause the cathode-ray beam to traverse the plate 35 in a direction at right angles to that before described.

The resultant action between the magnetic fields and the electrostatic fields upon the oathode beam is such that the beam covers every point in the whole area. of the composite plate 32 in of a second, that is, in cycle of the frequency generated by the altemating-current generator 23. Thus, in of a second, the cathode beam traverses the surface of the composite plate twice.

As the cathode beam traverses the surface of the composite plate 32 point by point in a definite sequence, there is a current flowing from the grid 39 and the aluminum foil 36 at each particular point, and this current is directly proportional to the intensity of light from the object to be observed. Thus, the oscillatory current generated by 'the oscillator triode 9 is modulated in accordance with the light from each portion of the image.

At the receiving station, the modulated oscillatory currents generated by the oscillator 9 of the transmitter are received by the antenna and transferred to the detector triode 53 through the transformer 52. The detector triode 53 then operates to detect the modulations and then these are transferred through its plate circuit to the grid 54 of the cathode-ray tube 55.

By means of the transformer 63, associated with the oscillating circuit 58, the modulated radio-frequency current generated by oscillator i8 is received and transferred by transformers 65 and 66 in the detector triodes 57 and 68. By the operation of the transformer 65, only the radio frequency that is modulated by the generator 22 is detected. In a like manner, by the operation of the transformer 56, only the radio frequency modulated by the generator 23 is received by the detector triode 58.

As the plate circuit of the detector triode 61 is connected to the plates 58 and 59 in the oathode-ray oscillograph 55, an electrostatic field is set up by these plates which varies in identically the same manner as the electrostatic field generated by the plates 25 and 26 in the transmitting cathode-ray tube. Likewise, the plate circuit of the triode 68 is connected to the coils 69 and which generate a magnetic field parallel to the electrostatic field generated by the plates 58 and 59 and that varies in exactly the same manner as the magnetic field set up by the coils 28 and 29 at the transmitting station. Thus, when the cathode-ray beam passes through the grid 55 and the anode 51 to the fluorescent screen 60, it is caused to traverse a path in accordance with the resultant magnetic and electrostatic fields set up. Therefore, the cathode-ray beam traverses the whole area of the fluorescent screen once in of a second, or twice in 1 g of a second, in the same manner as the cathode beam in the oathode-ray tube 21 at the transmitting station.

When the cathode beam in the cathode-ray tube of the transmitter is in a certain particular position, the oscillatory current generated by the oscillator 9 is modulated in accordance with the intensity of the light falling upon that particular point. This modulated current is radiated by the antenna 3 and received by the antenna 5| .at the receiving station. At this particular point,

the cathode beam in the cathode-ray tube 55 will be in the same relative position as the oathode beam at the sending station. By the action of the grid 54, the intensity of the cathode ray reaching the fluorescent screen at this particular point is varied in accordance with the light from the image at the transmitting station.

Thus, for every particular point on the image, the'carrier current radiated by the antenna 3 is modulated whereby the potential on the grid 54 of the receiving cathode ray tube 55 is varied, as is, also, the intensity of fluorescence of the particular point upon the fluorescent screen 50. As the whole area of the composite plate 32 at the transmitting station and the fluorescent screen 60 at the receiving station is covered by the cathode beams in of a second, the image of the object will be displayed on the screen 60 during of a second. However, as the frequency of the oscillation of the generator 23 is 16 cycles per second, the picture will be transmitted twice and will remain on the screen Bil during of a second. Thus, due to the persistency of vision phenomena, any movement of the object before the lens 31 will be properly transmitted and recorded upon the fluorescent screen 60 and will appear thereupon as a moving image. Of course, in place of transmitting the image of actual objects, it is entirely possible to send moving pictures, as all that is necessary is to pass the pictures before the lens 31 at the required rate and a replica of them will appear on the screen 60. In order to place these pictures before a large audience, it is, of course, poss ble to intensity and focus them upon an ordinary screen by means of any well known optical system.

The operation of the system when the apparatus used in Fig. 3 is employed at the transmitting station is very similar to that already described. The cathode beam covers the area of the fluorescent screen under the influence of the magnetic and electrostatic fields. When the beam is at one particular point, the light from that spot will traverse the film l8, lens Ti and photoelectric cell i6.

The variation of current of the photoelectric cell 16 causes the carrier frequency to be modulated in accordance with the current flow which hil is directly proportional to the intensity or" light from the fluorescent spot that reaches the photoelectric cell. As this condition occurs for each particular point on the picture, the whole picture will be transmitted in the manner described. The method of reproduction is the same as has been explained in conjunction with Figs. 1 and 2.

The intensity of the cathode beam may be regulated by regulating the voltage of the alternating-current sources ill or 62 in a well known manner.

Attention is drawn to the fact that any change in the frequency of operation of the alternatingcurrent generators 22 and 28 at the transmitting station causes a corresponding change in the frequency of oscillations in the current affecting the cathode ray at the receiving station, and, consequently, the cathode-ray beams will-remain in synchronism at both the transmitting and receiving stations and there will be no distortion in the picture transmitted.

It is obvious that it is entirely possible to have the alternators 22 and 23 generate a synchroniz-' ing frequency at a station separate from the transmitting station. In this case, the central synchronizing station would be arranged in the manner shown in Fig. 4. The alternators I22 and M3 correspond to the alternators 22 and 23. These alternators serve to modulate a frequency generated by the oscillating circuit including the oscillator triode H8, and this modulated frequency is radiated from the antenna H13 in the usual manner.

At the transmitting station in Fig. 5, the operation is the same as has been before described, with the exception that the oscillatory circuit "it is resonant to the synchronizing carrier frequency, and this frequency is transferred to the transformers W5 and "it of the detector triodes N17 and 868. By the operation of these detectors, the synchronizing frequencies are applied to the coils we and Elli and to the plates Ill and H2. The further operation of the system takes place in the same manner as has been described before.

It will be seen that this arrangement permits a number of transmitting stations to transmit pictures or visual indications with only one central station for generating the synchronizing frequency.

It is, of course, apparent, that any number of receiving stations may receive the image broadcasted in a manner similar to that described.

My invention is not limited to the particular arrangement of apparatus illustrated but may be variously modified without departing from the spirit and scope thereof, as set forth in the appended claims.

I claim as my invention:

1. In a television system, the combination with a transmitting and a receiving station, of an analyzing device comprising a cathode ray scanning device including a plurality of elemental storage-devices at said transmitting station, a cathode-ray scanning device at said receiving station, an object, and means including said. cathode ray devices for reproducing an image of said object at said receiving station.

2. In a television system, the combination with a transmitting and a receiving station, of a cathode ray-scanning device at said transmitting station, a cathode-ray scanning device at said receiving station, two sources of high-frequency current at said transmitting station, detecting devices at said receiving station, an object at said transmitting station, means for modulating said second source of high-frequency current at two difierent frequencies, means controlled by said current of two frequencies for moving said cathode ray at said transmitting station, means including said detecting device at said receiving station for moving the cathode ray thereat, means controlled by the cathode ray at said transmitting station for modulating said first high-frequency current in accordance with the intensity of light at various portions of the object, and means at the receiving station for causing said cathode my to reproduce an image of said object.

3. In a system for the transmission of intelligence, the combination with a transmitting station, and a receiving station, of apparatus at both stations for generating cathode rays, said apparatus at the transmitter comprising a source of voltage, a source of electrons, a perforated conductor having a hole through which electrons from said source pass, together with means for preventing the electrons passed through said hole from following divergent paths, electrical means at the stations for deflecting the cathode rays in any direction to cover any point on a plane, an image on one plane at the transmitting station, a screen at the receiving station, means for varying the electrical means at the transmitting station to cause the cathode rays to cover the area occupied by said image, means for simultaneously varying the electrical means at the receiving station to cause the cathode rays there to scan said screen and means for altering the intensity of the cathode beam in accordance with the light intensity of the image to reproduce the image on the said screen.

4. In a viewing device for a television system, a screen comprising a layer of photoelectricallyresponsive material divided into a plurality of elementary areas and a surface of conducting material normally insulated therefrom and means for establishing conduction successively between different elementary areas of the photoe'lectrically-responsive layer and the conducting surface.

5. In a viewing device for a television system, a screen comprising a layer of photoelectricallyresponsive material, a surface of conducting material and a layer of solid insulating material sepj arating said layer from said surface, and means.

for rendering said insulating material conducting at the points of the screen successively.

6. In a viewing device for a television system, a surface bearing photoelectrically-responsive material, an insulating support for said surface and electronic means for establishing electric conduction through said insulating support at a single point.

'2'. In a viewing device for television systems, a cathode-ray tube, a photoelectric cell and a continuous partition separating them, said partition comprising a wall, whereby said wall will afford conduction through said partition at only the point subjected to the cathode ray.

8. In a viewing device for television systems, a screen, means for producing an image on one face of the screen, means for causing a cathode ray to explore the other face of the screen, and means between the faces for establishing conduction transverse to the screen at each point while the cathode ray acts at said point and preventing conduction at other times.

9. The method of operating a cathode ray device having a member whose resistance varies with the illumination thereof which comprises forming on the member an image of the picture or view to be transmitted, causing the cathode ray to scan the member, and producing current variations in accordance with the resistance of successive elemental areas of the member engaged by the cathode ray.

10. Apparatus for the character described comprising a resistance element, whose resistance varies with its illumination means for forming an image on the element, and means comprising a movable cathode ray for including in an electric circuit successive small areas of said element.

11. In a picture transmission system, means for producing a beam of cathode rays, a target in the path of said beam, means for causing the beam to explore said target, said target having a conductive body on the face thereof toward said beam, a photoelectrically-sensitive body on the face thereof away from said beam and normally insulated from said conductive body and means whereby the beam will establish a conductive connection between said bodies at the point where the beam contacts the target, a circuit including said two bodies, said connection established by r the beam, a portion influenced by the illumination of the photoelectrically-sensitive body and a translating device and excluding all portions of said beam not part of said conductive connection.

12. An apparatus for transmitting pictures, motion-pictures or direct-vision, comprising a cathode, an anode of tubular form, a circuit connecting the cathode and the anode, and including a source of potential, means for deflecting the stream of electrons emitted by the cathode, a photo-electric layer over which said electron stream as deflected is adapted to pass and upon which the picture is adapted to be focused, and a circuit connecting the photo-electric layer and the cathode.

13. In an electro-optical image producing system, a bank of condenser elements, means for charging said condenser elements in accordance with the tone values of difierent elemental areas, respectively, of a field of view having tone values extending over a range of values between fixed limits, a transmission medium, and means for associating said condensers one at a time in succession with said transmission medium to produce an electric wave having amplitude variations corresponding to the variations in tone value of the elemental areas of said field of view for controlling the production of an image of said field of view.

14. The method of signaling which comprises energizing a light sensitive device in accordance with the characteristics of an elemental area of a visual representation, controlling a storing device in accordance with the response from said 21:2 .2 sensitive device, and connecting said storing a transmission channel. A plurality of light-current translating deimpulse storing element in circuit with plurality of light-sensitive ells, an inimpulse storing element in circuit with ell, and a commutator for connecting the elements into a common circuit.

In a light-current translating device, an

plane divided into electrically-separated teary areas, a separate storing element in circuit with each area, and means for connecting said storing elements into a common circuit.

18. In a light-sensitive device, an image plane divided into individual light-sensitive elementary areas, an impulse storing element for each of said elementary areas, and adapted to be energized in accordance with the characteristics of the associated area, and means for connecting said storing element in succession to a common circuit.

19. The method of signaling which comprises energizing a light sensitive device in accordance with the characteristics of an elemental area of a visual-representation, controlling a storing device in accordance with the resistance from said light sensitive device, and connecting said storing device to a transmission channel.

20. The method of signaling which comprises simultaneously energizing a plurality of separate light sensitive devices, each device corresponding to an elemental area of a visual representation, controlling storing devices in accordance with the operation of the associated light sensitive devices, and connecting the storing devices to a transmission channel.

21. The method according to claim 20, in which the storing devices are controlled simultaneously by the associated light sensitive devices and storing devices are connected successively to the transmission channel.

22. The method of transmitting a visual representation, which comprises translating the characteristics of the elemental areas of the representation into electrostatic charges, and applying said charges to a transmission channel.

23. The method of transmitting a visual representation which comprises simultaneously translating the characteristics of a plurality of elementary areas of the representation into corresponding electro-static charges, and successively connecting said charges to a common transmission channel.

24. In a system for transmitting visual representations, the combination of a plurality of light sensitive devices, means for projecting on said devices an image of the representation to be transmitted, means for translating the responses of said device into corresponding electric charges, and means for applying said charges to a transmission channel.

25. The method according to claim 24 in which the charges are connected to the transmission channel in succession.

26. In a system for transmitting visual representations, a plurality of light sensitive devices, means for projecting upon said devices an image of the representation to be transmitted, an electro-static storing device associated with each light sensitive device, a transmission channel, and means for successively connecting each of said storing devices to said channel.

27. A system according to claim 26 in which the means for connecting the storing device to the transmission channel includes a continuously operating commutator.

28. View-reproducing apparatus which comprises means for forming by photo-electric action an electrical distribution determined in intensity at each elementary area by a view to be transmitted, and electronic-stream scanning means for causing elementary areas of said distribution to be scanned in succession and the electricity of said distribution to be conducted to a workcircuit to constitute a train of electrical energy in accordance with the intensity of the elementary areas of the electrical distribution being scanned and means to deflect said stream.

29. In a view-reproducing device having a photo-electric screen which comprises a sheet of insulating material surfaced on one side by a layer of discrete particles of photo-electric material, means for focusing a view to be reproduced upon said screen, means for producing an electron-beam which has in the region of said screen a relatively small cross-section, and means for causing said electron beam to scan said screen.

30. In a view-reproducing device, a surface of photo-electric material and means for focusing an image of the desired view thereon, a collectorelectrode for the electrons photo-electrically emitted from said screen, electronic-stream scanning means to cause electric charges generated at different elementary areas of said surface to flow successively in a work-circuit between said surface and said collector electrode, and means to deflect said stream.

31. In a view-reproducing system, a screen surfaced on a side facing said view with a photoa target comprising a layer of insulation faced' on one side with a conducting sheet and having on its other face discrete particles of a material which is sensitive to radiant energy, said target being positioned to intercept said electron-beam,

and a collector-electrode insulated from said target.

34. In combination with a vacuum-tight container, enclosing means for producing an electron-beam therein, a target comprising a layer of insulation faced on one side with a conducting sheet and having on its other face discrete particles of a material which is sensitive to radiant energy, said target being positioned to intercept said electron-beam, a collector-electrode insulated from said target. means to project rapidly-varying optical images on said target, means to cause said electron-beam to scan said target, and a work-circuit connected between said target and said collector-electrode.

35. In combination with a vacuum-tight container, enclosing means for producing an electron-beam therein, a target comprising a layer of insulation faced on one side with a conducting sheet and having on its other face discrete particles of a material which is sensitive to radiant energy, said target being positioned to intercept said electron-beam, a collector-electrode insulated from said target, means to project changing optical images on said target, means to cause said electron-beam to scan said target in success'ive periods shorter than the persistence of human vision, and a work-circuit connected between said sheet and said collector-electrode.

" 36. The method of signalling which comprises energizing a light-sensitive device in accordance with the characteristics of an elemental area of a visual representation, controlling a storing device in accordance with the response from said light-sensitive device, and deflecting an electronbeam to connect said storing device to a transmission channel.

37 In an electro-optical image producing system, a bank of condenser elements, means for charging said condenser elements in accordance with the tone values of different elemental areas, respectively, of a field of view having tone values extending over a range of values between fixed limits, a transmission medium, and means for producing an electron-beam and for deflecting it to connect said condensers one at a time in succession with said transmission medium to produce an electric wave having amplitude variations corresponding to the variations in tone value of the elemental areas of said field of view for controlling the production of an image of said field of view.

38. In an electro-optical image producing system, a bank of condenser elements, means for charging said condenser elements in accordance with the tone values of different elemental areas, respectively, of a field of view having tone values extending over a range of values between fixed limits, a transmission medium, and means for producing an electron-beam and for causing it to scan said condenser element and thereby connect them within the period of persistence of human vision one at a time in succession with said transmission medium to produce an electric wave having amplitude variations corresponding to the variations in tone value of the elemental areas of said field of view for controlling the production of an image of said field of view.

39. In a view-reproducing system, a screen surfaced on one side with a material which is sensitive to radiant energy, means for focusing the entire area of said view on said material and electronic-stream means to produce current-flow in a work-circuit in accordance with the intensity of light on successive elementary areas of said view, and means to deflect said stream.

40. For use in the reproduction of a visual scene the combination comprising a photo-electric layer, means for forming an image of said scene on said layer, a fixed cooperative electrode associated with said layer and electron means for causing the photo-emissive charge produced at elemental areas of said layer by said image to flow from each said areas in its turn in a predetermined timed sequence to said electrode.

VLADIMIR K. ZWORYKIN.

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