| 摘要 |
PURPOSE:To control current supply to a driving source, make the front curtain and rear curtain of shutter traveling at a constant speed during expodure and prevent an image from uneven exposure by detecting counter electromotive force generated in an electromagnetic driving source at the time of shutter traveling. CONSTITUTION:In a shutter of this invention curtain speed is gradually increased similarly with a curve A during the period from a travel starting point 0 to t1. However if counter electromotive force exceeds a fixed value, current flowing into a coil 14 is reduced in accordance with the increment of counter electromotive force, the coil is rotated at a constant speed within a fixed range and a shutter curtain travels also a fixed speed within the range. Thus images are prevent from uneven exposure by detecting counter electromotove force generated in an electromagnetic driving source by setting up time so that a slit forming line enters an opening for exposure after the time t1 that the curtain speed of the front curtain and rear curtain reaches a fixed speed after starting traveling and comes out from the opening at the time t2 before the reduction of the curtain speed. |
