| 摘要 |
PURPOSE:To reduce variance in the quantity of light controlled according to the variance among light receiving elements by placing plural light receiving elements nearby a light emission source and approximating the quantity of light to a target value by the light quantity feedback of the light receiving elements. CONSTITUTION:Control is performed by using the mean value of a light receiving element 1 and a light receiving element 2, so the quantity of light is A'. The light quantity feedback is performed by a single light receiving element in a conventional light quantity control system, so the light quantity of light is controlled to B at the time of using the light receiving element 1 if a light quantity feedback circuit is so formed that the quantity of light is A while the value of a reference light receiving element is (a). Further, when the light receiving element 2 is used, the quantity of light is controlled to C. For the purpose, plural light receiving elements (2 elements 1 and 2 in this example) are placed nearby the light emission source and the quantities of light of the light receiving elements are fed back to approximate the quantity of light to the target value.
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