| 摘要 |
PURPOSE:To eliminate photographic fogs on an image surface, by detecting the electric potential at the background of the image on the surface of a photosensitive body when the image is not exposed, calculating the quantity of difference of the detected electric potential of the background section from a reference and the changing rate of the electric potential in the lapse of time, and controlling the appropriate electric potential at the surface of the photosensitive body when the image is exposed. CONSTITUTION:Transmitting light from, for example, a microfilm is given to a copying mechanism section C through an optical scanning mechanism. A sensor 19 is installed to the next of an entire surface exposure lamp 14 and detects the surface potential of a photosensitive drum 1 after entire surface exposure treatment is performed. The detected potential value is inputted in an arithmetic circuit 21 and the detected value is compared with a preset reference potential value, and then, a correcting value for charging is calculated from the difference between the detected value and reference value and the changing rate of the electric potential in the lapse of time. Then outputs of discharging devices 12 and 13 are corrected in accordance with the calculation. During the period when a slit 96 is closed by a light shielding member 91 and a drum 10 is shield from lights at every cycle, the electric potential at the dark section of the drum 10 is detected and correction and control of the electric potential of the drum are performed. Therefore, photographic fogs at the image surface and jumps of thin characters and fine lines can be eliminated. |
