GB641309A - Improvements in or relating to colour television systems - Google Patents

Abstract

641,309. Television. COMPAGNIE POUR LA FABRICATION DES COMPTEURS ET MATERIEL D'USINES A GAZ. March 4, 1948, No. 6784. Convention date, March 6, 1947. [Class 40 (iii)] In a colour television system wherein the individual colour components of a picture are scanned in sequence, electronic storage devices are each fed with image signals representative of one colour and are arranged to be rendered operative in sequence so as to supply modulation for transmission when image signals of a different colour component are being transmitted. By this means signals due to each colour component may be transmitted continuously at a frequency high enough to avoid colour flicker and stroboscopic effects. The two-colour system illustrated operates at 50 frames per second and employs a camera C with two complementary colour filters inserted alternately in the light path. The camera signals pass to two electronic storage tubes A1 and A2 through an electronic commutator E synchronized with the alternation of the colour filters so that the image on each tube mosaic is renewed every <SP>1</SP>/ 25 th second. The tubes may be of the ionoscope or orthicon type with two scanning beams, one to produce the stored picture and the other for analysis to generate an output signal. Alternatively a single beam may function for both purposes. The arrangement is such that, during the scanning of the first colour frame, the signals pass to the corresponding receiver channel R1 through an amplifier D1 and are also stored in tube Al, the output circuit of which is blocked. During the following scanning of the complementary colour, the input to tube A1 and amplifier D1 are both blocked but the output of A1 is unblocked and feeds into channel R1. This results in signals due to the first colour being passed continuously into channel R1 at a repetition rate of 50 per second. Storage tube A2 and amplifier D2 function likewise for the complementary colour signals in channel R2. In a three-colour system the images on the storage tube mosaic are renewed every <SP>1</SP>/16th second and the tubes adjusted so that only partial discharge occurs during each scan.