| 摘要 |
PURPOSE:To reduce the burden of an operator with respect to exposure mode selection to reduce the generation rate of copy failures by monitoring a certain time after power-on, the end of one copying operation, or manual mode setting by a timer and setting automatically the automatic exposure mode when the copying operation is not executed within this monitor time or the power source is turned on. CONSTITUTION:A keep relay RL provided with a set terminal S and a reset terminal R constitutes a setting means of the automatic or manual exposure mode. When the keep relay RL is set, the automatic exposure mode is set; but when it is reset, the manual exposure mode is set. When the automatic exposure mode is set, a copying machine detects optically the density of an original on an original platen and adjusts an exposure in accordance with this density. With respect to automatic exposure setting, a slit is formed on the original platen, and an optical sensor is arranged under the slit, and the reflected light from the original which passes the slit is detected by the sensor, and the voltage of a light source is hanged in accordance with the density. When this operation is performed for all regions of the original moving on the slit, an optimum exposure is attained in each position of the original passing the slit. |
