| 摘要 |
PURPOSE:To attain sure white-level balance adjustment even when the aperture of a diaphragm is changed manually by providing an automatic white level balance adjustment circuit. CONSTITUTION:The automatic aperture control circuit 2 controlling the diaphragm 5 of a motor-driven diaphragm device 1 consists of an error signal generating circuit 12 detecting an error signal from an image pickup output, e.g., a luminance signal Y and an arithmetic circuit 13 comparing an aperture state detection signal from a potentiometer 14 as a voltage sending circuit generating a voltage in response to the aperture state of the diaphragm and the error signal to control a motor 6, and the potentiometer 14 is connected between a power supply +B4 and the ground. A switch SW1 has a slider (r) connected to one terminal of the motor 6, an automatic aperture control fixed contact (a) connected to the power supply +B2 and a manual aperture variable fixed contact (m). A switch SW3 is the 3rd switch operated in interlocking with the 2nd switch SW2 and operates the automatic aperture control circuit 2 forcibly regardless of the interruption of the automatic aperture control circuit 2 by the switch SW1.
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