| 摘要 |
PURPOSE:To set an exposure time properly with a simple constitution, by setting the exposure time in accordance with switching of gamma to two kinds of value with a gamma switching luminance as the boundary to make an auxiliary aperture mechanism unnecessary. CONSTITUTION:When the luminance of an object is in a low luminance region, the output of a comparator 11 becomes ''1'' because a voltage Va of a connection point (a) is lower than a voltage Vb of a connection point (b), and an analog switch 13 becomes conductive, and the voltage Vb is supplied as a low luminance region reference voltage to a comparator 4, and the exposure time is set in an exposure time setting part A in accordance with gamma=1. When the luminance of the object is in a high luminance region higher than the gamma switching luminance index, the voltage Va is higher than the voltage Vb, and the output of the comparator 11 becomes ''0'', and an analog switch 14 becomes conductive, and the voltage Va is supplied to the comparator 4, and it is held in a high luminance region reference voltage, and the exposure time is set in the setting part A in accordance with gamma=0.5. |
