GB566429A - Improvements in television transmitting systems - Google Patents

Abstract

566,429. Television; cathoderay tubes. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. July 26, 1943, No. 12134. Convention date, July 27, 1942. [Classes 39 (i) and 40 (iii)] Relates to television transmitting systems in which scene is illuminated by a fluorescent lamp energized by alternating current and is projected on a photo - sensitive target electrode scanned by a cathode-ray, and consists mainly in providing a portion of the inside wall of the cathode-ray tube with a photo-sensitive layer adapted to receive light from the fluorescent lamp and thereby to release photoelectrons to said target electrode to compensate undesirable signal variations arising from the inherent cyclic variations in the light from the fluorescent lamp. As shown, the scene illuminated by the fluorescent lamp 42 is projected by a lens system 14 on the photosensitive target 12 scanned by the electron gun 16 with beam-deflecting means 18. The tube includes a collecting electrode 25, and the inside surface of its wall around the target electrode is coated with caesium arising from the process of sensitizing the silver globules of the target electrode. Incandescent lamps 34, 35, 37, 38 with apertured shields 32 are arranged to project light on the sensitized wall of the tube and on the edge of the target. The tube and the lamps are enclosed in a light-tight housing 45 having an aperture 47 through which light from the fluorescent lamp 42 passes to reflectors 51 directing this light to the sensitized wall of the cathode-ray tube. The aperture 47 may be regulated by an adjustable shutter 49, and the incandescent lamps, which are fed from a source 40, may be regulated by variable resistors 36,39.