EXPOSURE CONTROLLING METHOD OF IMAGING CAMERA

摘要

PURPOSE:To set exposure time properly by generating a signal for specifying a photometric area with delay corresponding to the time of arrival at the photometric area in response to a horizontal and a vertical synchronizing signal, and measuring variation in the brightness of the area automatically. CONSTITUTION:A composite synchronizing signal from a CRT display device 1 is separated into the horizontal and vertical synchronizing signals, which are inputted to monostable multivibrators MH1 and MV1 and further MH2 and MV2 to generate pulses for specifying the horizontal and vertical addresses of the photometric area. A sampling signal Samp and a nonsampling signal Samp' are generated by pulses from the MH2 and MV2. A signal from a photodetecting element 18 is ampled by the signal Samp. Once a shutter is released with an exposure button, a switch S3 is opened and an integrator I1 integrates the sampled signal and also counts a clock signal. When its integral output exceeds a reference value, a comparing circuit CP1 generates a high level and the current counted value Cl is stored. A controller closes the switch S3 and calculates a proper exposure counted value C2 by using a value C1 to close the shutter at the time of the value C2.