| 摘要 |
PURPOSE:To obtain a stable latent image potential and to keep stable and excellent image quality even when a photosensitive body is fatigued by detecting the surface potential of the photosensitive body and the latent image potential of a reference pattern and setting the latent image potential of a reference pattern white part higher than the residual potential of the photosensitive body. CONSTITUTION:Electrification amount and exposure amount are controlled so that detected potential of a black part pattern 17a and a white part pattern 17b on a contact glass 10 by means of a potential sensor 16 are 800V and 100V, respectively. That is, the grid voltage of an electrification charger 2 is adjusted so as to control the detected potential of the black part pattern and the voltage of an exposure lamp 11 is adjusted so as to control the detected potential of the white part pattern. Thus, a curve B can be obtained with respect to a curve A showing an initial state by correcting black part detected voltage VD and white part detected voltage VL by means of the residual detected voltage VR of the photosensitive body after lapse of time. The electrification amount and the exposure amount are controlled according to the curve B. Thus, the lowering of the image quality can be prevented which is caused by the fatigue of the photosensitive body. |
