| 摘要 |
PURPOSE:To improve the accuracy in time control for an exposing time by correcting the exposing time in a control circuit device for shutter time of a digital control system with the half period of a clock pulse as a reference. CONSTITUTION:The clock pulse signal (a) obtainable from an oscillating part OSC is used as a reference for measuring an exposing time. A trigger switch Tr transmits a trigger signal (b) synchronized with the start of traveling of a shutter front curtain. A time measuring circuit Q measures the prescribed time by counting either of the trailing edge or leading edge of the signal (a) right after reception of the signal (b) and transmits an exposure completion signal for running a shutter rear curtain. The variable time since the running of the shutter front curtain till the exposure completion signal by the asynchronization of the signal (b) and the above-mentioned one edge signal to be counted in a latch circuit R may become shorter by more than half the period of the signal (a) than the longest time since the running of the shutter front curtain till the exposure completion signal owing to the syncronization of both signals. If such is detected, the time is corrected so as to be kept within the half period of the signal (a) and the correct exposure completion signal is transmitted. |
