| 摘要 |
PURPOSE:To suitably control a diaphragm for extracting a binarized image by gating the binarized image with a mask signal read out from a mask memory storing mask areas other than noticed section in a prescribed visual field, extracting the luminance level of said noticed section, and controlling it to be constant. CONSTITUTION:An image signal read out from an image pickup element is amplified by a video amplifier 4 and inputted to a comparator 5. The other terminal of the input of this comparator 5 is connected to a reference voltage source Vref. By the comparator 5, a video signal is obtained by binarizing the image signal in '1' or '0'. The binarized video signal is inputted to a gate circuit 6 from which, the logical product of a binarized image signal outputted form the comparator 5, a mask signal mask from the mask memory 11, and a clock signal CLK to count picture elements. The binarizing image is gated with a signal MASK from the memory 11, a mask area in the image is stored, then the areas other than the noticed section in the image are masked.
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