GB1419771A - Colour motion picture film playback system - Google Patents

Abstract

1419771 Image pick-up tubes RCA CORPORATION 6 March 1973 [17 March 1972] 12696/72 Heading H1D [Also in Divisions H3-H5] In apparatus for providing luminance and chrominance colour television signals, e.g. N.T.S.C. from a colour cine film 12, Fig. 1, the image of two successive frames 14 and 15 are projected on to respective targets of a television camera tube 18, the targets being formed from half discs and being scanned by respective beams from electron guns 21, 22 the scanning rasters being exactly the same due to a common deflection system 23, the first frame 15 being projected on to the upper target 19 via a colour encoding striped filter 26 to provide the chrominance signal at output 24 and the second frame 14 being projected on to the lower target 20 to provide the luminance signal at output 25. The luminance signal, having a bandwidth extending up to 3À5 MHz Fig. 2b, is extracted by low pass filter 40, Fig. 3 and fed to adder 39. The spatial filter 26 produces two chrominance signals 28 (e.g. red and blue) quadrature modulated on a 2 MHz carrier, Fig. 2a and a narrow band reference signal 27 at 1 MHz. These two signals are processed together to cancel out any errors due to scanning or filter inaccuracies. The chrominance signals and the reference signal are respectively extracted by band-pass filters 32 and 36. The chrominance signal has its carrier shifted to 5À58 MHz by mixing at 33 with the output of oscillator 34 and then to 3À58 MHz by mixing at 35 with the frequency doubled reference signal from multiplier 37. The chrominance signal now on the standard carrier of 3À58 MHz is combined with the luminance signal at adder 39 for modulation on the V.H.F. carrier at 41. Instead of being on the target face of tube 18, the spatial filter may be provided adjacent the films, Fig. 4 (not shown) or in the centre of a lens projection system, Fig. 5 (not shown) such that the film's image is focussed on the filter and the image of film and filter is in turn focussed on the targets.