GB1341139A - Circuits for the quality of a colour television signal - Google Patents

Abstract

1341139 Colour television NIPPON COLUMBIA KK 28 Oct 1971 [28 Oct 1970(4)] 50221/71 Heading H4F In a colour television camera using two striped colour filters to produce an image which when scanned gives rise to two separable colour component signals each modulated on to a subcarrier of frequency determined by the stripe spacing of the associated filter, an arrangement for reducing the effects of crosstalk due to partial overlap of the frequency bands of luminance and chrominance signals is provided. As shown in Fig. 13 the output from camera pickup tube 6 is fed to low-pass filter 7 to extract a luminance signal and to band-pass filters 8, 9 tuned to the two colour subcarriers. The colour signals pass via delays 10, 11 to subtractors 12, 13 which also receive correction inputs, their outputs then passing to a mixer 14 deriving the three primary colour signals. At rapid changes of luminance a circuit 15 differentiates the input signal and produces pulses of period t 0 (having a spectrum similar to that of luminance changes) which are processed at 16 to produce unidirectional pulses. These are transmitted via band-pass filters 20, 21 (similar to 8, 9 respectively) to produce signals which reduce at 12, 13 the effect of spurious cross-talk components. An arrangement for generating two sets of correction signals based on rapid chrominance changes in the two colour channels and applying them each to the other channel is described (Fig. 15, not shown); in this case the correction pulses each have widths (and thus spectra) chosen in accordance with the channel spacings. Fig. 22 (not shown) illustrates an arrangement in which the pulses generated by rapid luminance changes act to close a gate for a colour signal, to sample the delayed colour signal at a slightly later instant (when it is free of crosstalk components) and insert this sample in place of the blocked colour signal, the colour channel including an appropriate delay to enable this to be done.