| 摘要 |
PURPOSE:To automatically set the optimum bias voltage in each condition and to obtain stable image quality, by detecting potential of the electrostatic latent image of a patch image having prescribed density formed on a photosensitive material, and compressing developping bias voltage corresponding to this value. CONSTITUTION:A patch 3 having prescribed density is applied to a platen 1, surface potential of the electrostatic latent image of this patch 3 is detected with a potential sensor 16, and a voltage similar to this detected potential is impressed to a developing roll 10 in a developing device 9 through a bias voltage source controller 17. When developing potential changes due to change of cycle characteristics, and temp. characteristics of the photosensitive material, aging change of exposure, light intensity change due to stains of an optical system, the optimum developing bias voltage is impressed in accordance with those changes. |
