GB1092881A - Improvements relating to colour television apparatus - Google Patents

Abstract

1,092,881. Colour television signal generation. ELECTRIC & MUSICAL INDUSTRIES Ltd. Jan. 31, 1964 [Jan. 31, 1963; May 16, 1963], Nos. 3977/63 and 19422/63. Heading H4F. [Also in Division G2] Component colour images 3, 4, 5, Fig. 1, are formed in side-by-side position on the target of a pick-up tube and scanned as one image at one third of the standard line scanning rate so that the component colour signals are generated line sequentially at the standard line rate, the signals thereafter being directed into separate channels 9, 10, 11 by switch 8 and converted into simultaneous signals by further switches which operate in conjunction with pairs of delay lines 17, 18, 21, 22 and 24, 25, each line of which introduces a delay equal to the duration of one standard scanning line. A second camera 51 produces a luminance signal, the frame scanning of the two cameras being controlled by a common generator 58 and the line scans being controlled at standard and one-third standard rate by separate generators 55, 54. In a second arrangement, Fig. 2, the colour camera has a target formed of mutually insulated strips corresponding to the standard scanning lines each provided with a colour filter, the colours being arranged in the repeating sequence R, G, B, R etc. Connections to the target strips of the same colour are commoned. The target is scanned at the standard rate and thus produces line sequential colour signals with the components in separate channels. Simultaneous signals are produced as before by delay lines 36. In a third arrangement, Fig. 3, a normal undivided target is employed in the pick-up tube with a filter formed of a repeating sequence of red, green and blue strips, but the filter has the red and blue strips divided by vertical opaque lines, the number employed for the blue strips being substantially greater than that employed for the red strips. The target is again scanned at the standard rate so that the colour component signals appear in sequence at line rate, but the signals are distinguished in that the green signal is a normal video signal whereas the red and blue signals are carrier signals of different carrier frequency. The signals are separated by low-pass and band-pass filters 43, 44, 45 and (after demodulation in the case of the red and blue signals) rendered simultaneous by delay line circuits (not shown) arranged as in Fig. 2. The green signal channel includes undesired red and blue components which are eliminated by cross-coupling the channels. The need for this is avoided in a fourth, similar arrangement, Fig. 4 (not shown), in which the green filter strips are also divided so that the green signal appears as a carrier signal. In connection with the third and fourth embodiments there is described with reference to Figs. 5-8 (not shown) an optical system in which the filters comprise pairs of filters located away from the focal plane. This system forms the subject of Specification 1,092,882.