Patent ID: 6882363

Claim:
A video signal processing apparatus comprising: automatic gain controlling means for controlling a gain of an AGC circuit which receives a video signal from an imager having an electronic shutter function in accordance with a gain control signal; average detecting means for detecting an average luminance level of said video signal; gain control signal generation means for generating said gain control signal in such a manner that said average luminance level becomes a prescribed constant value; and shutter speed control signal generation means responsive to a mode signal indicative of cycles per second of an ac line for generating a shutter speed control signal at a unit of a voltage variation cycle of said ac line; wherein: a shutter interval of said imager decided by said shutter speed control signal generation means is selected, in accordance with an output from said average detecting means, from among one or more values of integer multiples of a time period of said voltage variation cycle within a storing cycle of said imager; said gain control signal outputted from said gain control signal generation means is controlled stepwise, at said unit of said voltage variation cycle of said ac line, on the basis of said shutter intervals outputted from said shutter speed control signal generation means; and said gain control signal outputted from said gain control signal generation means is made inversely proportional to a changing ratio of said shutter intervals outputted from said shutter speed control signal generation means.