Patent GB-1453963-A (GB)
Title: Colour television camera
IPC: H04N9/077
Filed: 1973-11-07
Abstract: 1453963 Colour television SONY CORP 7 Nov 1973 [9 Nov 1972] 51726/73 Heading H4F The output signal from a one-tube colour television camera incorporating a striped colour filter 14 is split by frequency filters 21, 24 into luminance and chrominace components; to compensate for non-linear amplitude characteristics of the luminance component a signal derived by detecting at 52 the amplitude of the chrominance component is fed via a level adjuster 53 to a subtraction circuit 51 to be subtracted from the luminance component. The chrominance component from frequency filter 21 is passed via one-line delay lines 25, 26 and phase-shifters 31-34 to adders 37-39 to provide separate red, blue, green signals from the outputs of detectors 41, 42, 43; these red, blue, green signals are added at 54 to provide a signal which is fed via a level adjuster 55 to subtraction circuit 51 to be subtracted from the luminance component to provide a luminance component with increased sharpness. The luminance component is fed from frequency filter 21 to subtraction circuit 51 via a delay 22 providing either a one-line delay or a delay equal to that provided by the colour demodulators. The red, blue, green signals from 41, 42, 43 may be fed to a circuit 56 wherein each is multiplied by the ratio of the luminance component from subtraction circuit 51 to the signal from 54 to provide wide-band red, blue, green signals which are fed to an NTSC coder 60. The colour filter 14 is formed with three sets of stripes, one set having alternate transparent stripes and red-blocking stripes, a second set having alternate transparent stripes and blueblocking stripes, and the third set having alternate transparent stripes and green-blocking stripes. In a first embodiment (Fig. 1, not shown) the width of a transparent stripe in each set of stripes is half the pitch of that set and the stripes are such that the resulting red, green and blue carriers are all at the same frequency, the blue carrier having a phase change of 0 degrees between scanning lines, the red carrier having a phase change of + 120 degrees between scanning lines, and the green carrier having a phase change of - 120 degrees between scanning lines, the carriers being separated using a circuit as shown in Fig. 4, using 120 degree phase delays 31, 34 and 120 degree phase advancers 32, 33. In a second embodiment the filter 14 (Fig. 12, not shown) is such that the width of a transparent stripe in each set of stripes is half the pitch of that set and the stripes are such that the red and blue carriers are each at half the frequency of the green carrier, the green carrier having a phase change of 0 degrees between scanning lines, the red carrier having a phase change of + 240 degrees between scanning lines and the blue carrier having a phase change - 240 degrees between scanning lines. The green carrier is separated by a band-pass filter (23, Fig. 15, not shown), the red carrier being derived from adder 37 receiving signals directly from delay line 25, via a 240 degree phase delay from filter 24 and via a 240 degree phase advancer from delay line 26, the green carrier being derived from adder 39 receiving signals directly from delay line 25, via a 240 degree phase advancer from filter 24 and via a 240 degree phase delay from delay line 26.