| 摘要 |
PURPOSE:To compensate the change in the photocurrent during traveling of a shutter front curtain with a simple constitution and make exposure control of high accuracy possible by controlling differential amplifiers according to the change in the photocurrent during traveling of the front curtain thereby maintaining integrated current at a prescribed constant value. CONSTITUTION:When a mirror is kicked up cooperatively with shutter operation, an analog switch 18 closes, and a capacitor 22 is charged by the photocurrent I from a photodiode 10 based on the reflected light from the front curtain surface. Thence, if the current I from the diode 10 changes according to traveling of the front curtain, the reference current Iref1 changing according to the change in the current I is applied to a differential amplifier 76 via differential amplifiers 20, 26, 36, etc., and the integrated current I2 applied upon a capacitor 84 based on the equation I is compensated of the change in the current I and is maintained at a constant value at the start of the front curtain traveling. Hence, there is no used for increasing the reflectivity of the shutter front curtain, the exposure of a film by stray light is prevented and the exposure control of high accuracy is accomplished with the simple constitution. Iref2 herein indicated denotes constant current. |
