GB594327A - Color flicker reducing apparatus for color television receivers - Google Patents

Abstract

594,327. Television receivers. FARNSWORTH TELEVISION & RADIO CORPORATION. April 19, 1945, No. 9862. Convention date, Feb. 28, 1944. [Class 40 (iii)] To reduce the " colour flicker " observed in a colour television system wherein a plurality of coloured filters transmit light of successive primary colours from an image on a reproducing screen, coloured light from an additional source or sources is transmitted in alternation with light from the image.. As shown in Fig. 1, an image is formed on the screen of the cathode ray tube 11 in front of which rotates a disc 26 carrying the colour filters. The disc is driven by synchronous motor 27 the power supply for which is developed from the field synchronizing signals. The disc as shown in Fig. 2 comprises filters 29, 31, 32 which transmit light from the cathode ray tube screen, and also auxiliary light transmitting members 33, 34, 35, one 33 of which is shown in the operative position in Fig. 1. It consists of transparent material, the front surface of which is roughened, and the back surface polished and also silvered if desired. A colour filter 37 is attached to its peripheral edge. A lamp 39 emits light intermittently so that it illuminates only the elements 33, 34, 35. Thus during each interval between the display of two coloured images, the auxiliary light transmitting member will transmit diffuse light of the third primary colour. The rate of production of each colour is doubled and flicker is reduced. The filters 29, 31, 32 may be shielded so that lamp 39 may emit continuously. In alternative embodiments each light transmitting member may comprise sectors containing all three primary colours or three separate coloured light sources may be used. It is also possible, by the use of suitable optical devices to make the colour filters perform the functions of the light transmitting members so that these latter may be dispensed with.