| 摘要 |
PURPOSE:To obtain an automatic diaphragm with less influenced from a high luminance object due to backlight condition, etc. by comparing a luminance signal takenout of an image pickup signal with a prescribed threshold and driving a dia phragm driving circuit with the luminance signal from which the component of the luminance signal exceeding the prescribed threshold outputted from a comparator is eliminated. CONSTITUTION:A luminance signal 20 on which a gamma correction etc. is applied at a process circuit 19 is also supplied to a comparator 23 and is compared with a threshold voltage from a threshold voltage generator 24. The luminance signal exceeding the threshold voltage is decided as the video signal corresponding with the high luminance object and the threshold voltage is outputted from the comparator 23. Therefore, the luminance signal in the output of the comparator 23 used for the control of the automatic diaphragm is the one from which the component with high luminance is eliminated. The output from the comparator 23 is detected at a detector 25 having a detecting characteristic near to a peak detection and is made as a DC signal. The DC signal is impressed on a diagragm driving circuit 26 as a control signal to control the automatic disphragm. The circuit 26 drives a diaphragm control motor 27 with the impressed control signal and opens and closes a diaphragm feather 16. Therefore, it is possible to image pickup with an appropriate exposure.
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