| 摘要 |
PURPOSE:To keep the whole exposure always constant, by arranging each optical fiber bundle terminal to fluorescent lamps to detect the light quantity and controlling power supply to the lamps in accordance with the output synthesized. CONSTITUTION:The terminals of the bundles 6, 7 of an optical fiber cable 8 are arranged to fluorescent lamps 2, 3 illuminating an original face, and the other terminals illuminate the photodiode 9 of a control circuit 10, resulting in generating a photocurrent almost proportional to the sum of the light quantity received by the original. When the intensity of the lamps 2, 3 decreases with this constitution, the photocurrent of the diode 9 drops, and this change is compared with a reference voltage through operation amplifiers 11, 12. When the photocurrent decreases, the differencial becomes higher, the impact coefficient D of output pulse of a pulse modulator 13 increases, extending a conduction time of a switching circuit 27 and raising lamp powers. Vice versa when the photocurrent is larger, permitting the whole exposure to be kept always constant. |
