| 摘要 |
PURPOSE:To simplify constitution and to reduce the size of a feed-back part by controlling a thyristor corresponding to a voltage developed across an exposure lamp and according to a photocurrent generated by the photocoupler of a voltage feedback part, and thus controlling the quantity of lamp light. CONSTITUTION:The exposure lamp 4 is connected to an AC power source 21 through a bilateral thyristor 22 and the photocoupler 27 is provided to the voltage feedback part. The voltage across the exposure lamp 4 is converted by a rectifier 23 into a current, which operates the photocoupler 27. Then, the photocurrent generated by a photodetecting element 29 is converted by an A/D converter 33 into digital data, which is sent to a microcomputer 35. The microcomputer 35 operates its internal timer according to the level of the input data to generate a trigger pulse, with which the turn-on angle of the thyristor 22 is controlled to control the quantity of lamp light. Consequently, the constitution is simplified and the size of the voltage feedback part is reduced. |
