DEVELOPING BIAS CONTROLLER

摘要

PURPOSE:To prevent fogging on a ground part when image procesing to give gradation to copying density is executed, to prevent the generation of BCO in developer and to stabillize highlight density by providing a means correcting the drift of measureed back ground potential accompanying image processing. CONSTITUTION:The potential difference between the back ground potential V of a photosensitive body 18 subjected to image processing and the back ground potential V of the photosensitive body 18 not subjected to image processing is previously obtained and the potential difference becomes the drift correcting quantity DELTAVHSET of the measured back ground potential. Then, the corrected back ground potential is obtained by adding the drift correcting quantity DELTAVHSET to the back ground potential V subjected to image processing while copying cycle is executed at measurement mode. Developing bias is controlled so that the difference between the developing bias potential VBIAS and the corrected back ground potential is held constant at all times.