Patent GB-1204368-A (GB)
Title: Colour television image pickup system
Inventor: TAKEMURA YASUO
IPC: H04N9/04
Filed: 1967-11-07
Abstract: 1,204,368. Colour television cameras. TOKYO SHIBAUKA ELECTRIC CO. Ltd. 7 Nov., 1967 [10 Nov., 1966; 18 Jan., 1967; 8 Feb., 1967; 8 March, 1967], No. 50651/67. Heading H4F.  Light from an image is divided by a beam splitter 12, Fig. 1, into a first beam, which passes to a pick-up tube 13 to produce a luminance signal, and a second beam in which a first colour component image is maintained intact whilst a second colour component image is divided into a striped pattern. The second beam passes to a second pick-up tube 18 with the stripes at right-angles to the line scanning direction whereby the tube develops a signal having a low frequency component representing the first plus second colour components and a modulated carrier signal representing only the second colour component. As illustrated, the first colour component is red and the second blue, although this order may be reversed. The green component is eliminated by a dichroic reflector 15, whilst the division of the second component into stripes is effected by a filter 17 having alternate sections (shown clear and shaded) which transmit respectively red plus blue, and red light. Since the green component is eliminated by reflector 15, the spectral characteristics of filter 17 are not critical and the red strips may be replaced by yellow (i.e. red plus green) strips. Filter 17 may be a reflective filter. In order to restrict the frequency band of signals produced by pick-up tube 18 the optical system may be arranged (or may include means) to blur the optical image presented to the tube. The signal components are separated by filters 19, 21 and the carrier demodulated at 22. A matrix circuit 20 then responds to the two component signals R + B and R together with a luminance signal Y obtained through filter 27 to derive component colour signals R, G and B. Beam splitter 12 may apportion 30% of the image light to the luminance tube 13 and the remainder to the colour tube 18. A filter may be included in the light path between splitter 12 and tube 13 which, in conjunction with the spectral characteristic of the tube, is arranged to produce the correct composition for the luminance signal (i.e. a signal Y compounded of the colour components R, G and B according to the equation Y= 0À59 G + 0À30 R + 0À11 B). Modifications are described. In Fig. 9 (not shown), filter 17 immediately follows relay lens 14 in the optical path and is before dichroic reflector 15. Beam splitter 12 is replaced by a prism assembly. In Fig. 10 (not shown), relay lenses 14 and 16 both appear before reflector 15 and filter 17 is located between the lenses. In Fig. 12 (not shown), the relay lenses and dichroic reflector are dispensed with. The second (reflected) light beam from splitter 12 passes only through filter 17 to tube 18 which is disposed at right-angles to tube 13. Fig. 14 (not shown) is similar to Fig. 9 described above but employs a simple (non-selective) reflector in place of the dichroic reflector. In Fig. 15, filter 17 is replaced by a multi-element cylindrical lens screen 36 operated in conjunction with two dichroic reflectors 33 and 34 which reflect light components as indicated. The order of the reflectors may be reversed.