| 摘要 |
A signal processing circuit comprises an image sensor having an optical black level detecting portion, a buffer circuit for receiving an output signal from the image sensor, a clamping circuit for receiving an output from the buffer circuit, and a low-pass filter provided between the buffer circuit and the clamping circuit. This low-pass filter is made operative by a switching circuit in the interval responsive to the black level detecting portion in the output signal of the image sensor, while it is made inoperative in the interval responsive to the image pickup signal detecting portion. According to this circuit, the black level drift can be followed, thereby preventing the appearance of line noise on the screen without being influenced by the sag component due to the AC coupling.
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