GB477561A - Improvements in television, and the like - Google Patents

Abstract

477,561. Television transmission. MICHAELIS, E. July 20, 1936, No. 20015. Convention date, July 20, 1935. [Classes 39 (i) and 40 (iii)] The object E is imaged on a photo-electric cell cathode B so that the brightest parts of the object produce saturation emission of electrons, and the cathode B is scanned by a beam of light from J which is intense enough to produce saturation emission in the absence of other illumination. If the object is not bright enough to produce saturation emission, the cathode is uniformly illuminated from another source, while if the object is too bright, a filter is interposed to reduce the intensity of the image. The steady current through K in the absence of a scanning beam is proportional to the intensity of the object; on scanning, this current is increased by the difference between the saturation emission of a scanned point and its emission before scanning, and this variation is used as the picture signal. The variations in the steady current due to variations in the contents of the object are eliminated by circuits similar to automatic fading arrangements, e.g. a condenser may be charged by the steady voltage at the end of each complete scanning and the condenser potential then used to bias the succeeding amplifier or a grid within the photo-electric cell. The object may radiate infra-red rays, so that the receiver and transmitter may be utilized for observing invisible objects. The scanning beam may be derived from a cathode ray traversing a fluorescent screen. Specification 426,505, is referred to.