| 摘要 |
PURPOSE:To improve operativity while obtaining the best exposure automatically according to fluctuations of a power voltage and various originals, by providing an artificial load circuit, wave-form shaping circuit, photodetecting circuit, error amplifier, and limiting circuit. CONSTITUTION:The voltage that corresponds to the voltage across exposure lamp 2 is generated by artificial load circuit 33 and waveform-shaped by waveform shaping circuit 34, and photodetecting circuit 38 converts reflected light from an original into a voltage signal. The output voltage of photodetecting circuit 38 is added to the output voltage of this circuit 34 and the sum is supplied to error amplifier 37, where it is compared with a prescribed voltage to control the quantity of light of exposure lamp 2 corresponding to the comparison result while control circuit 40 controls the output of amplifier 37 according to the output voltage of circuit 34. Thus, the best exposure can automatically be obtained, so that while the operativity is improved, the voltage applied to exposure lamp 2 can automatically be limited to lower than a constant voltage at any time. |
