| 摘要 |
PURPOSE:To obtain a copied substance which does not have surface fogging and which has sufficient density even though the image density of an original is thin and background is colored. CONSTITUTION:A first pre-exposing device 13 selectively switching a pre- exposing unit 13a with long wavelength (610nm) and a pre-exposing unit 13b with short wavelength (565nm) is arranged in the periphery of a photosensitive body 1; furthermore, a potential sensor 5 is disposed. A first controller 60 is connected to the potential sensor 5, and a light source 19 irradiating the consecutive paper original 50 of a feeder 30 (density is thin and density irregularity exists much) is connected to the controller 60. The minimum value (minimum surface potential) of an electrostatic latent image formed on the photosensitive body 1 by a main electrostatic charger 2, and an exposing means 15, etc., is detected by the potential sensor 5, and the first controller 60 controls the light source 19 and sets the value to a specified potential level at which the surface fogging does not occur. By that, developing contrast is apt to be small, but the developing contrast can be sufficiently secured by switching the pre-exposing device 13 to the short wavelength side. |
