| 摘要 |
PURPOSE: To securely prevent misdetection due to soil on an optical detection means resulting from the replacement of a toner storage part by detecting the optical density of the base part of an image carrier by the use of an optical density detection means before the replenishment of a developing device with toner after the detachment of a toner storage part, and comparing an optical density detection value relating to this detection with a reference value for use in comparison. CONSTITUTION: By providing the photosensor 4 further downstream than the developing device 2 in the direction of the rotation of a photoreceptor 1, the optical density of a reference image formed on the photoreceptor 1 is detected when controlling toner concentration during image formation. When a toner cartridge 10 is replaced or a toner forcible replenishment switch is depressed, toner is forcibly added into a developing part 11 by means of an agitator 12 in the toner cartridge 10. During this forcible replenishment operation, the optical density of the base part of the photoreceptor 1 is detected by the photosensor 4, and a required amount of toner is added based on the comparison of the detection result with the reference density, thereby exerting control so that required toner concentration is obtained. |
