Patent GB-315362-A (GB)
Title: Improvements in television apparatus
IPC: H04N5/68
Filed: 1929-07-10
Abstract: 315,362. Tihanyi, K. July 12, 1928, [Convention date]. Void [Published under Sect. 91 of the Acts]. Vacuum tubes.-Television apparatus comprises a light-sensitive surface on which an image is projected and an electrical radiation influenced by the changes in the light-sensitive material. A homogeneous cathode ray k1, Fig. 1, is produced in a tube 1 by passing the rays through an aperture in a diaphragm g, a deflecting magnetic field m and a second aperture. The rays explore an electrode Tr coated with selenium, zinc sulphide and copper, or other light-sensitive materials, including liquids, through deflection produced by electrostatic fields applied to electrodes C, c, which are energized from a local aerial receiving oscillations produced in a transmitting aerial by an oscillation generator M. An image of the object to be transmitted is projected on the lightsensitive material through a spot filter Ff. This filter neutralizes irregularities in the coating and is produced by photographing the image produced at the receiver when the electrode Tr is illuminated uniformly. The anode currents resulting from the variations in the resistance or other property of the light-sensitive material in accordance with illumination are passed to a transmitter 6. At a receiver, Fig. 2, a concentrated cathode ray k2 is controlled in accordance with the received signals, by passing it round a positive filament 102 surrounded by a negative cylinder 101, the potential of the filament being controlled by the received signal. The image is produced by phosphorescence produced on a screen L by the cathode rays. Light from the image passes through a spot filter Ff to a light intensifier BV. This comprises a selenium or other light-sensitive layer of which the changes in electric properties control a neon glow or a stream of cathode rays impinging on a phosphorescent screen so as to produce a brighter image (Figs. 26, 27, 43 - - 46, not shown). According to modifications, a metallic grid is placed above or below the selenium layer to produce an alternating-current imposed on the picture currents to facilitate amplification; the selenium is deposited on a wire gauze, or as a grid on a transparent metallic gauze, so as to act as a control grid for the cathode rays (Figs. 7 - - 10, 19, 38, 39 and 40, not shown) ; the sensitive layer or the electrode has a number of superficial points (Fig. 13, not shown); the sensitive layer consists of crystals, the electrical orientation of which is influenced by light (Figs. 11 and 41, not shown) ; the electrode consists of an electrolyte (Figs. 15 and 16, not shown); the capacity of the electrode is increased by placing metallic screens or the like near it (Fig. 17, not shown); the electrode reflects the cathode rays (Figs. 20 and 21, not shown); the phosphorescent screen is placed outside the tube and connected electrically with it by high-frequency currents (Fig. 22, not shown); the disturbing effect of secondary electrons is eliminated by surrounding the cathode ray path with metallic cylinders (Figs. 24, 25, and 37, not shown); in the image intensifier a selenium grid is arranged between two glow electrodes (Fig. 28, not shown), one of which may be heated and the other a phosphorescent screen (Fig. 29, not shown); the heated electrode is between a photoelectric screen and a phosphorescent screen (Fig. 30, not shown); the phosphorescent screen lies between a photo-electric screen and a transparent counter-electrode (Fig. 31, not shown); a spacecharge grid is arranged between the selenium screen and a counter-electrode (Fig. 32, not shown); the glow is produced by separate electrodes (Fig. 33, not shown); a phosphorescent layer is coated directly on a selenium layer (Fig. 47, not shown); the selenium layer is outside a glass vessel and electrically connected with an internal electrode by high-frequency currents (Fig. 48, not shown); both electrodes are outside the vacuum space (Fig. 49, not shown); a cylindrical intensifier is used (Fig. 50, not shown); a mercury vapour intensifier is used (Fig. 51, not shown); the selenium layer is coated on one side with a transparent electrode and on the other with a grid electrode covered by a layer perforated between the grid filaments to prevent the formation of spots in the picture owing to irregularities in the selenium coating (Fig. 53, not shown); the effect of changes in electron speed in the cathode ray tube is neutralized by varying the strength of the deflecting electrostatic fields in accordance with the electron speed (Fig. 55, not shown) or by means of an additional electric field (Fig. 56, not shown); the apparatus is adapted to colour reproduction (Fig. 57, not shown); the cathode ray is concentrated by oppositely directed magnetic fields on opposite sides of the ray (Figs. 60 and 61, not shown); the phosphorescent screen is excited to the point of phosphorescent by separate radiation (Fig. 62, not shown); the scanning is controlled by varying the electrostatic fields by revolving contacts altering the resistance in the circuits (Fig. 63, not shown), or by a dynamo (Fig. 64, not shown); the movement of the cathode rays is reversed by special electrodes at the limits of their travel (Figs. 65 and 66, not shown); the synchronizing is produced by means of signals of greater intensity than the picture currents transmitted at the limits of travel of the cathode rays (Figs. 67 and 68, not shown).