Automatic diaphragm control device for a closed circuit television camera

摘要

An automatic diaphragm control device for with a closed circuit television camera is disclosed in which a video output signal from the television camera is applied to a polarity-inversible amplifier. The video output signal is then rectified by a voltage doubling rectifier and a DC voltage thereby obtained is compared with a separately provided reference voltage to form a diaphragm control signal. A voltage, which charges a capacitor responsible for voltage doubling in said rectifier, may be adjusted to achieve changeover of the light measuring mode so that the voltage doubling rectifier operates in an average mode when adjusted in the direction of the average light measuring mode relative to the initial state and operates in a peak mode when adjusted in the direction of the peak light measuring mode relative to the initial state.