| 摘要 |
PURPOSE:To obtain a stable image at any magnification, by controlling the voltage to be applied to a light source in accordance with setting magnification to adjust exposure in a copying machine having a magnification changing fuction. CONSTITUTION:The stabilization circuit of an exposure lamp is provided, the voltage of lamp LA and the reference voltage received by terminal T1 of differential amplifier 20 are compared, and phase control is carried out by trigger pulses produced from trigger producer 30 in accordance with the output of amplifier 20 in response to the voltage difference. The lamp voltage, namely the brightness of the lamp LA is thus controlled. Exposure control following magnification is achieved by changing this reference voltage. When magnification is selected by a switch in the reference voltage supply circuit connected between terminals T1 and T2, signals lowered in voltage at each predetermined rate from the voltage of terminal T2 are delivered to terminal T1 as a reference voltage. The color temperature change of lamp LA due to applied voltage change is corrected by inserting a filter in the light path of an optical system. |
