| 摘要 |
PURPOSE:To improve image quality by making developing bias variable and keeping effective developing bias constant with reference to the electrostatic charging potential of a photosensitive body. CONSTITUTION:An image signal outputted from a scanner part 11 makes a printer part 13 form an image on a transfer paper through an image processing part 12 based on the image recording information of each color. At least one of the developing bias of a developing unit 26, the electrostatic charging potential of a photosensitive drum 24 and the writing light quantity of a write unit 22 is controlled based on the detection information of a sensor pattern forming means which is constituted of the processing part 12 and the write unit 22, etc. Meanwhile, after or before performing an image forming action, the processing part 12 controls the developing bias of the unit 26 to have a fine potential difference with reference to the ground potential of the photosensitive body so as to be reverse to the magnitude in ordinary image forming, and the image is developed on the photosensitive body by the developing device of the above developing bias and the developing bias is variably controlled so as to make the density detected value by a sensor constant. |
