GB610722A - Improvements in colour television and photographic apparatus - Google Patents

Abstract

610,722. Colour television. RADIO CORPORATION OF AMERICA. Nov. 14, 1945, No. 30419. Convention date, Dec. 16, 1944. [Class 40 (iii)] [Also in Group XX] In a colour television system comprising a plurality of colour separation filter elements, the elements have conjointly variable colour absorption ratios from substantially full colour to a substantial transparency, whereby the degree of colour saturation introduced by the system may be controllably varied. The invention is applicable to systems wherein the filters are either sequentially or simultaneously operative. In a system where each component colour is selected sequentially, a filter 11 in the form of a rotating disc is divided into three portions transmitting red, green and blue light respectively. The filter is constructed so that the outer edges of the disc allow light of sub, stantially one colour only to pass, but as the centre of the disc is approached more and more white light is transmitted until at the centre the filter is substantially transparent. The disc is driven by a motor 23 synchronized with the remainder of the television system and mounted on a base 33 which may be elevated or lowered by a rack and pinion (not shown). The light from an object, following the path 27, passes through the filter and a lens system to the television camera 45, the output of which comprises video signals to which are added synchronizing and blanking signals in the unit 50. When the filter is fully elevated, black and white pictures are transmitted and when it is fully lowered, the pictures are in full colour, the degree of saturation being indicated by a pointer 39. A crank and lever is attached to the base 33 to vary a gamma or contrast control in the unit 48 to suit the degree of colouration of the picture transmitted. A colour filter 31 such as that disclosed in Specification 599,134 may be inserted in the light beam path to provide colour balance. In a modification, Fig. 2 (not shown), the colour separation filter comprises a drum in the form of a frustum of a pyramid. In Fig. 5 (not shown) is illustrated a filter constructed so that the transparent portions are at its peripheral edge. Fig. 3 (not shown) illustrates a system in which the colours are selected simultaneously, the light beam being split into a number of paths in each of which is placed a filter, these filters being operable together from a single control. The separate light beams are applied to a plurality of television cameras or to a single camera with a plurality of targets and the signals from the cameras are either selected sequentially and transmitted over a single channel or transmitted simultaneously over a plurality of channels.