| 摘要 |
PURPOSE:To obtain a copy image whose image density is not lowered, whose ground is not stained, and whose contrast is good, by always holding the potential difference of white and black, even if a photosensitive body is fatigued and deteriorated, the surface potential drops, and the residual potential increases. CONSTITUTION:A surface potential sensor 4 detects the surface potential of a photosensitive body 1, and is inputted to a comparator 18 through the contact (a) of a switch 17. Subsequently, a voltage corresponding to the surface potential required for a black part is outputted by a reference source 20, inputted to one input terminal of the comparator 18, and compared with the output of the surface potential sensor 4. The output of its comparator 18 is brought to a level adjustment by an amplifier 22, inputted as the control signal of a high voltage power source 3 through the contact (c) of a switch 25, and the output of the high voltage power source 3 is varied. Subsequently, an exposing system 16 is operated, light is irradiated to an object to be photographed 14 of a white reference density, irradiated onto the photosensitive body 1 electrified through the optical system 3, and an electrostatic latent image corresponding to the object to be photographed 14 of the reference density is formed. |
