| 摘要 |
PURPOSE:To perform high-accuracy exposure control by obtaining the timing where a stepping motor is driven in the reverse direction from a timer means which begins to clock the time at the start of actual exposure and then clocks the time corresponding to an exposure value for obtaining proper exposure. CONSTITUTION:Sectors 12a and 12b being to open and a timing switch S1 is turned on when exposure is started actually. Then, the Q terminal of an FF 45 rises to a level H and a binary counter 46 starts counting clock pulses supplied from an oscillation circuit 35 through an AND circuit 47. When a digital value from the binary counter 46 reaches a digital value X from a ROM 33, namely, when an aperture reaches an aperture position where optimum exposure is obtained, a comparator 34 outputs a stop pulse 48 to a line (5). The counted value of the binary counter 42 is reset to '0-0-0' in the middle. Consequently, the stepping motor reverses to rotate the sectors in the closing direction.
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