Patent GB-1193712-A (GB)
Title: Colour Signal Generating Apparatus
IPC: H04N9/07
Filed: 1967-06-15
Abstract: 1,193,712. Colour television. SONY CORP. 15 June, 1967 [15 June, 1966], No. 27706/67. Heading H4F. [Also in Division G2] In a colour relevision camera utilizing a single pick-up tube, the image is resolved into colour components by means of a colour filter system and focused on the tube target through a multiple lens element, the arrangement being such that the colour components are formed on the target in overlapping relationship with at least one component varying in optical density in the line scanning direction in a predetermined cyclic manner. In a first arrangement the image is resolved into colours by a filter, Fig. 7B and focused on the pick-up tube target 3, Fig. 8, by way of a cylindrical lens screen 9 having the axes of the lenticules at right-angles to the line scanning direction. The filter is divided into green (17G), cyan (17C), yellow (17X) and transparent (17W) sections, the boundaries of which are defined by two sinusoidal curves having periods in the ratio 1 : 2 and extending about an axis, at right-angles to the axis of the lenticules of screen 9. The effect of the filter in conjunction with lens screen 9 is to produce on the pickup tube target green image light 18G with a uniform intensity distribution in the line scanning direction, red image light 18R with a sinusoidal distribution and one maximum per lenticule, and blue image light 18B with a sinusoidal distribution of half the period of the red distribution and hence two maxima per lenticule. Upon scanning the tube, the green information appears as a normal video signal whilst the red and blue informations appear as carrier signals with frequencies in the ratio 1 : 2. The signals may be readily separated by filters and the carriers demodulated to obtain simultaneous colour signals. To enhance uniformity of colour distribution in the direction of the lenticule axes the filter may be formed of a plurality of sections similar to Fig. 7B disposed side-by-side, Fig. 9 (not shown). The filter construction may be simplified to a series of parallel strips, Fig. 10 (not shown), but this gives rise to harmonics of the component colour. signals and militates against their separation. A more complex form of filter, Figs. 11A and 11B (not shown), is based on Fig. 7B but introduces uniform distributions of the red and blue light as well as green whereby the colour carrier signals are accompanied by an equal energy type of luminance signal. In a second arrangement of the invention, Fig. 12, analysis of the image light into component colours is effected by filters 17R, 17G, 17B which are located in separate light paths. The operation is similar to the unitary filter of Fig. 7B in that the green filter 17G imposes a uniform light distribution transverse the lenticule axis of screen 9, the red filter 17G imposes a variable distribution exhibiting one maximum, and the blue filter 17B imposes a variable distribution exhibiting two maxima. In a modification, Fig. 13 (not shown), the colour analysis is effected by uniform filters, or by choice of the beam splitting elements 22-24, and the non- uniform light distribution in the red and blue paths is brought about by the inclusion of cylindrical lens elements. As an alternative to forming the lens screen 9 on or as part of the pick-up tube face plate 2, as illustrated in Fig. 6 (not shown), it may be separated therefrom by a relay lens and/or optical fibre assembly, Figs. 16-18 (not shown). Modifications of the lens screen are described with reference to Fig. 14 (not shown). Instead of using cylindrical lenses, the screen may be formed of a mosaic of spherical lenses, Fig. 15 (not shown). Reference is made to the use of selective reflectors for colour analysis.