| 摘要 |
PURPOSE:To obtain a copy image having no ground stain from an original with a normal color ground or a faithful copy image from an original whose density is deeper than a fixed value by holding the surface potential of a photosensitive body equal regardless of whether the density of the original is deeper or lower a preset low and a high original image density value. CONSTITUTION:Respective means for electrostatic charging, exposure, transfer, destaticizing and cleaning are provided at the circumference of the photosensitive body, and part of reflected light from the original to be copied is detected by using the photodetecting element 12 of an original image density detecting means during before-exposure scanning before copying operation. Its detection output is compared by comparing means 23, 24, and 33 with reference voltages. Then, an automatic control means for the surface potential of the photosensitive body controls the surface potential of the photosensitive body according to comparison results to hold the surface potential of the photosensitive body equal for the original having density lower than the preset low original image density and an original having density deeper than the preset deep original image density. |
