development of colour television cameras.

摘要

1,099,739. Colour television. COMPAGNIE FRANCAISE DE TELEVISION. July 28, 1966 [July 30, 1965; Nov. 29, 1965], No. 34050/66. Heading H4F. In a colour television transmitter for transmitting a SECAM type (Trade Mark) composite video signal in which two pre-emphasized colour signals A 1 and A 2 , e.g. (R-Y)/K 1 and (B-Y)/K 2 respectively, are linearly frequency modulated on a subcarrier alternately at line frequency and passed through a coding filter whose gain increases on either side of a frequency Fc of the variation range of the instantaneous frequency of said frequency-modulated subcarrier, the signals A 1 and A 2 have different resting frequencies, Fo and FSP1/SPo respectively, positioned asymmetrically on either side of frequency Fc, and frequency Fc is positioned towards the instantaneous frequency of the subcarrier corresponding to the transmission of signal A 1 for the maximum algebraical value of the difference-signal R-Y. This positioning of frequency Fc which is towards the lower frequencies since K 1 is negative reduces the noise present in the highly saturated red portions of the picture. Fig. 1 shows the centre part of the gain vs. frequency wave of the coding filter. The minimum of the gain characteristic is located between FSP1/SPo and Fo but due to the positioning referred to above it is 40 kc/s. from FSP1/SPo and 116 kc/s. from Fo. The Specification describes in detail embodiments of transmitters, Figs. 2 and 3, not shown, in which the outputs of two harmonic generators having resonant frequencies Fo and FSP1/SPo are compared in a phase comparator with the output of a frequency modulated oscillator to develop control signals which are applied to the frequency modulated oscillator to modify its resting frequency in alternate lines when signals A 1 and A 2 are applied thereto. The Specification also describes a receiver, Fig. 4, not shown, which includes a decoding filter whose gain vs. frequency curve compensates for that of the coding filter in the transmitter.