| 摘要 |
PURPOSE:To obtain always copy images of the best quality automatically by giving a prescribed charging current and exposure voltage to an electrostatic charger and an exposure device in a prescan cycle to measure the latent image characteristic of a photosensitive body and correcting the current and the voltage in accordance with the measured value of the latent image characteristic to copy an original image in a copy cycle. CONSTITUTION:A control circuit 17 which controls exposure due to an illuminating lamp 10 and the charging current of an electrostatic charger 3 is provided for the purpose of obtaining always the best picture quality. A potential detector 20 which detects the potential of a dark potential part formed in a prescribed position of a photosensitive drum 1 with scanning light L is provided to face the surface of the photosensitive drum 1. This dark potential part is formed in the prescan cycle before execution of a series of blue, red, and green latent image forming processes. At this time, the control circuit 17 controls an exposure light source 22 and a charging power source 23 so that the exposure voltage and the charging current given from the exposure power source 22 and the charging power source 23 to the illuminating lamp 10 and the charger 3 are preliminarily set values. |
