GB621561A - Colour television system - Google Patents

Abstract

621,561. Television. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Oct. 12, 1945, No. 26759. Convention date, Oct. 12, 1944. Addition to 621,560. [Class 40 (iii)] In a colour television system, signals representative of component colours are controlled by signals representative of the intrinsic brightness of these colours. In the present invention, which is a modification of the invention in the parent case, in which the colour signals are transmitted either simultaneously over a plurality of channels, one for each colour component, cyclically with the brightness signals which are transmitted simultaneously over all channels or, alternatively, all signals are transmitted successively over a single channel, the colour signals are modified by the brightness signals and all signals are transmitted simultaneously over separate channels. The colour signals are generated by means comprising picture signal generating tubes 43, 61, 75, provided respectively with colour filters 41, 57, 71 through which an image of the object is projected by means of half-silvered mirrors 15, 17, 19. After initial amplification, the colour signals are fed to one grid of valves 91, 93, 95 respectively, to the other grid of each of which are fed brightness control key image signals generated in tube 27 in the optical paths of which is positioned an orthochromatic filter 23. The level of the control signals fed to the colour amplifiers 91, 93, 95 may be individually adjusted by means of potentiometers 105, 107, 109, to control the amplification of the component colour signals in accordance with the intrinsic brightness of the key image. The controlled colour signals and the brightness (key image) signals are transmitted simultaneously over channels R, B, G, K respectively.