| 摘要 |
PURPOSE:To prevent the deviation from a white balanced state by setting the rate of gain variation to color difference signals less than that to a luminance signal through an automatic gain adjusting circuit as a signal processing circuit for color images of subjects and performing gain control over the luminance signal and color difference signals. CONSTITUTION:The output signal of an image pickup tube is supplied to a preamplifier 1 and part of the output of the preamplifier 1 is passed through an LPF3 to obtain the luminance signal Y. The remainder of the output signal of the preamplifier 1, on the other hand, is passed through an LPF6 to obtain a signal YL, which is supplied to a matrix circuit 9. Then, three primary color signals R, G, and B are obtained from the output of the matrix circuit 9. Then those three primary color signals R, G, and B are supplied to gamma correcting circuits 10, 11, and 12 for gamma corrections to obtain signals R', G', and B', which are passed through a color difference matrix circuit 13 to obtain color difference signals R'-Y' and B'-Y'. Those luminance signal Y and color difference signals R'-Y' and B'-Y' are brought under the gain control of variable voltage gain GCAs 15, 16, and 17 which are associated with one another.
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