PURPOSE: To maintain appropriate brightness at a required image part by performing diaphragm adjustment setting only an arbitrarily set area as the target of light quantity measurement.
CONSTITUTION: Scanning information from counters 15, 25 and signals from latches 12, 13 and 30, 31 holding required upper/lower and right/left position information are inputted to comparators 16, 17 by a microcomputer 11 based on the vertical and horizontal synchronizing signals of an image-picked up video signal, and a video signal in a required rectangular area can be obtained via a gate circuit 18. The mean level of the signal from which a synchronizing signal component is eliminated is detected at a smoothing circuit 14, which controls the diaphragm driving circuit of an image pickup device as a light quantity signal. Thereby, it is possible to adjust the diaphragm quantity of an iris diaphragm mechanism replying to the brightness of a set area, and to eliminate the influence of the brightness to the outside of the area.
SAIKI MITSUYOSHI
SATO ATSUSHI
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