GB1331937A - Colour television display systems - Google Patents

Abstract

1331937 Colour television MULLARD Ltd 10 Nov 1970 [17 Dec 1969] 61516/69 Heading H4F A switchable colour filter F is switched at line frequency so as to pass sequentially the three primary colours red, green, blue and is placed in front of a black-and-white cathode ray tube provided with three guns G1, G2, G3 operating simultaneously so as to write three lines on the screen at one time, the guns being provided sequentially at line frequency with red, green and blue signals, so that each line on the screen has the corresponding red, green and blue information displayed on it in sequence. The guns G1, G2, G3 are fed from three switches SW3, SW2, SW1 actuated at line frequency between the red, green and blue outputs of colour decoders DC3, DC2, DC1. Decoder DC1 receives the direct video input, decoder DC2 receives the video input via a one-line delay line DL1 and decoder DC3 receives the video input via two one-line delay lines DL1, DL2. Instead of a three-gun cathode ray tube a one-gun tube may be used, the beam being spot-wobbled. NTSC or PAL signals may form the video input and a phase inverter may be used for a swinging burst signal, one inverter being provided for each decoder or one inverter for all three decoders. The filter F may be a hexamethylenetetramine or potassium tantalum niobate crystal between crossed polarizers. The picture on the cathoderay tube screen may be projected through the filter F on to a larger viewing screen with the aid of an optical system. Specification 1,331,938, which claims the circuit including input VI, demodulators DC1, DC2 and DC3, delay-lines DL1 and DL2 and switches SW1, SW2 and SW3 switched at line frequency, is referred to.