GB783746A - Improvements relating to reproducing apparatus for colour television systems - Google Patents

Abstract

783,746. Colour television. FERRANTI, Ltd. March 12, 1956 [Dec. 10, 1954], No. 35740/54. Class 40 (3). A three-colour television image reproducer comprises two cathode-ray tubes 11, 12, the first receives two colour signals, e.g. the red and blue signals, alternately via commutator 21 and has a screen 15 with a uniform spectral distribution operated in conjunction with a colour filter 23 having red and blue areas 24, 25, Fig. 2, occulted alternately by the bars 28 of a transversely oscillating mask 26 driven in synchronism with commutator 21 by mechanism 29, whilst the second receives the third signal, i.e. the green signal, continuously and displays a green image by use of a suitable phosphor material for the screen 16 or a filter 17. Filter 23 and mask 26 are located in a non-focal position in relation to a suitable optical system (not shown) for imaging the screen of tube 11 on to a viewing screen 22 or the eye of a viewer. Mechanism 29 may comprise the drive element of a moving-coil loud-speaker. The oscillation frequency, which is of the order of 10 kc/s., is preferably synchronized with the line or frame timebase to prevent crawling colour patterns. In an alternative arrangement, Fig. 3 (not shown), the two cathode-ray tubes are disposed at right angles and their screen images are combined on a common optical axis by disposing the filter and mask system at 45 degree and forming the faces of the mask bars remote from the filter with reflecting surfaces. In this arrangement, the mask is preferably held stationary and the filter oscillated. Reference is made to the use of a mosaic filter. The invention may be used with sequentially received colour signals, the filter being operated in synchronism with the sequentially received signals and the cathode-ray tubes being blanked during unwanted colour signals.