GB562334A - Improvements in colour television apparatus - Google Patents

Abstract

562,334. Colour television. BAIRD, J. L. Oct. 10, 1942, No. 14256. [Class 40 (iii)] A colour television apparatus comprises an electronic scanning system in which each frame is made up of successive lines of different basic colours, and successive frames are superimposed in such a way that individual lines are successively of different basic colours. In one arrangement, Fig. 1, the screen A of a cathode-ray tube is focused by a lens B on to a scene or surface E to be scanned. Three colour filters (Red, Blue and Green) D1, D2, 'D3 are provided, one for each third of the screen A. Three mirrors C1, C2, C3 are slightly inclined to each other to superimpose each third of the screen A on the same surface E. The scanning of the screen A is by 200 lines according to the sequence indicated in Fig. 2, the lines of each third being differently coloured by the filters D1, D2, D3. In the superimposed projection on the surface E, there will be 600 lines in alternate colours as indicated in Fig. 3, the first line being Red. For the next. frame, the scanning ray is deflected the space of one of these 600 lines, so as to make the first line Blue. For the third frame, the ray is again deflected to make the first line Green. This sequence is then repeated. Modifications utilizing other numbers of lines and interlaced successions of frames are briefly mentioned. For two-colour reproduction, the cathode-ray tube, described in Specification 562,168 may be used, opposite sides of different colours of a common screen being scanned in alternate lines.