| 摘要 |
PURPOSE:To perform an equal optical system drive even by using any lens unit by receiving a lens discriminating signal from a connector terminal and automatically changing over the response characteristic of a drive circuit for driving an optical drivie means in the lens unit at the time of exchanging the lens unit. CONSTITUTION:The video output of an image pickup tube 2 is conducted to a camera process circuit via a preamplifier 3 and also supplied to a peak detection circuit (or an average value detection circuit) 4. Herein. the DC video signal is supplied to a drive amplifier via an adder 5, an amplifier 6 from a connector 14, compared with a reference value ref and an iris motor 12 is driven by the error output thereof. The iris is controlled so as to be closed to a bright object and opened to a dark object by this automatic iris loop and the brightness of a screen is maintained substantially constant.
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