| 摘要 |
PURPOSE:To use a white balance circuit at the time of recording and reproducing by switching color difference signals and reproduced color difference signals of photographed video signals at the time of recording and reproducing. CONSTITUTION:Luminance signal Y from a video signal conversion circuit 16 are applied to an adder 22, and color difference signals R-Y,B-Y are are applied to input of a right angle two phase modulating circuit 28 through variable gain amplifiers 24,26. Outputs of amplifiers 24, 26 are gain controlled by a feedback loop consisting of a comparator circuit, an up down counter and a D/A converter, and becomes constant to a reference voltage Vref. A right angle two phase modulating circuit 28 right angle two phase modulates sub- carrier from an oscillating circuit 40 by color difference signals R-Y,B-Y, and supplies carrier chrominance signals (C signal) to the adder 22. On the other hand, Y signals restored from signals of a reproducing head 72 are returned to the adder 22, and C signals are returned to R-Y,B-Y by a demodulating circuit 91, and their amplitude is feedback controlled to constant by amplifiers 24, 26 and supplied to the input of the right angle two phase modulating circuit 28.
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