US 2158259 A
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Description (OCR text may contain errors)
May 16, 1939.
K. TIHANYI TELEVI S I 0N APPARATUS Original Filed June l0. 1929 INVENTOR KALMAN TIHANYI ATTORNEY Patented May 16 1939 UNHTED STATES TELEVISION APPARATUS Kalman Tihanyi, Budapest, Hungary, assignor to Radio Corporation of America, a corporation of Delaware Original application June 10, 1929, Serial No.
Divided and this application March 8,
1935, Serial No. 9,958. In Germany June 11, 1
The present invention relates to transmitting systems for electric television and picture transmitting apparatus and forms a divisional part of my copending application Serial No. 369,598, filed June 10, 1929, for an invention on Television apparatus.
As in the parent application, it is an object of the present invention to eliminate difliculties connected with the usually practiced methods of television wherein a beam of light rays is moved across a picture field to scan and reproduce an image. To accomplish this purpose, the beam of light rays customarily used in connection with such mechanical systems, as, for example, the Nipkow disk type system, is replaced by an electron beam, such as a cathode ray, and this produced electron beam is moved across the photoelectric surface upon which the picture to be transmitted is continually projected.
However, in contrast to the use of a single continuous photoelectric layer, I have provided a system of individual photoelectric layers or surfaces which are carried upon an insulating surface, such as a diaphragm, upon the opposite side of which is mounted a conducting plate so that as the light image falls upon the discrete photoelectric areas which are insulated one from the other by means of the insulating plate discrete electrostatic charges are produced between each elemental section of the photoelectric material and the back plate.
This invention is capable of assuming various forms, as has been shownin the parent application, but for the purpose of this present divisional application I have illustrated that form of system wherein the light image and the canning beam, which has been illustrated as a cathode ray beam, strike or impinge upon the photo-sensitive mosaic from the same side.
The invention in one of its preferred forms has been illustrated by the single figure of the accompanying drawing which shows one conventional form of arrangement which the invention may assume.
If reference is now made to the drawing, it will be seen that there has been provided a tube I having therein a mosaic structure conventionally designated 3. The mosaic structure, as was shown by my parent application, includes an insulating reflector surface 5 with distinct and electrically isolated photoelectric particles or areas 1 upon one side thereof. On the opposite side of the insulating member 5 from that which is coated by the photoelectric material there is provided a conducting plate member or surface 9 which is connected to ground H by meansof the conductor ii], for example. Light from an image ii, for example, passes through the optical system I1 and the window I9 of the tube so as to strike or impinge upon the photoelectric areas I. In reaching the photoelectric areas i the light is passed through a collecting grid element 2! which is connected to ground H by way of a suitable battery 23. Thus, as the light from the image I5 strikes the photoelectric areas the grid member 2 I, which is maintained at a positive voltage by means of the battery 23, collects the emitted photoelectrons and they are passed to ground at l I. The result is that charges are built up between the photoelectric elements i and the back plate 9 connected to ground and the total charge at each elemental area is proportional to the light brilliance of the related elemental area of the image subject l5.
As the image is projected upon the photosensitive mosaic it also is scanned by means of a cathode ray beam, for example, which is developed between the cathode 25 and the anode element 21 which is maintained at a positive voltage relative to the cathode by means of the battery 29 and the issuing electron beam designated 3| passing between the sets of deflecting plates 33 and 35 is caused to scan and impinge upon each section of the photoelectric surface 7 by the application of suitable controlling voltage to the deflecting electrodes of the system and the photo-sensitive areas i may thus be traversed in any desired and appropriate manner.
The anode member is so constructed that the issuing cathode ray beam designated 3! is suitably defined and focused upon the photoelectric areas I. When the cathode ray beam designated 3i strikes the photoelectric areas, it causes the positive charges to be neutralized so that each elemental area or section of the photoelectric surface is carried back to an equilibrium potential. It is assumed that this action takes place because of the fact that a positive charge has been accumulated upon the diilerent photoelectric areas 1 due to the loss of photoelectrons and because the electron beam itself is negative. The result is that the electron beam which is then directed or reflected from the photoelectric area 1 so as to pass into the Faraday cylinder or Perrin receiver 31, 39 will vary proportionally to the variance in charge on different sections of the mosaic 3 and thus the eifective beam current in an output circuit connected with the Faraday cage or Perrin receiver varies in accordance with the electrostatic charges between the photo-sensitive areas I and the conducting member 9.
As was shown in my parent application in connection with Figs 1 and 4, there is provided between the cathode element 25 and the collecting electrodes 31, 39 a suitable source of voltage herein designated 4| so as to collect the electrons and the resulting current flowing in the circuit including the cathode 25 and the collecting electrodes 31, 38, as varied by the intensity of light producing different charges upon the photo-sensitive mosaic 3, appears in the output circuit connected by way of the transformer 43 whose primary winding 45 is formed as a part of the connection between the cathode 25 and the collecting electrodes 31, 39 and whose secondary winding 41 is formed as a part of the output circuit and may be connected in any desired manner to suitable forms 01 amplifying devices.
Having now described one form of the invention and the manner in which it is believed the same may be operated, what is claimed and de sired to secure by Letters Patent is the following:
1. The method of electrical image transmission which comprises projecting a light image upon a photo-sensitive mosaic, producing over the entire area of the photo-sensitive mosaic discrete electric charges proportional to the intensity of light received from the elemental area of the subject whose light image is projected thereupon, scanning the photo-sensitive mosaic with an electron beam impinging from the same side as the light image, and controlling the intensity of flow of electrical energy in accordance with the charges produced by light falling upon the photosensitive mosaic.
2. A device for television scanning which comprises an envelope having therein an insulating member, a plurality of discrete electrically insulated photoelectric elements supported upon one side of the insulating member, a conducting member supported upon the opposite side of the insulating member from the photoelectric material, an image viewing window included as a part of the envelope through which a light image of a subject of which the electrooptical image is de- 2,158";2li9 l sired may be projected upon the photoelectric elements to produce, thereby a plurality of electric charges between each of the separate photoelectric elements and the conducting member, the said charges varying proportionally to the infalling light brilliance on related elemental areas of the in-Ialling light image, means to produce a cathode ray and to cause the ray to scan the photoelectric elements from the same side as subjected to the in-falling light image, and a collecting electrode for receiving the cathode rays passing beyond the photoelectric surface so that the current reaching the collecting electrode varies proportionally to the light brilliance upon the individual areas of the photoelectric surface scanned.
3. An electronic television scanning tube which comprises an envelope, a mosaic structure comprising an insulating member, a plurality of electrically independent photoelectrically responsive areas upon one side of the insulating member, and an electrically conducting surface adjacent the opposite side of the insulating member, an image viewing window forming a part of the envelope through which a light image of a subject of which the electrooptical image is desired may be projected upon the photoelectrically responsive elements to produce thereby a plurality of discrete electrostatic charges between the photoelectric area and the conducting surface, said electrostatic charges each being of an intensity proportional to the intensity of light image projected upon the photo-sensitive area through the viewing window, means to produce a cathode ray beam within the tube, means to deflect the ray according to a predetermined deflection pattern to cause the beam to scan the photoelectric elements from the same side as subjected to the in-falling light image, and an output circuit for collecting the cathode rays subsequent to their impinging upon the photoelectric surface so that the current in the output circuit varies in proportion to the brilliance of the light upon the photoelectric area instantaneously subjected to the electron beam.