| 摘要 |
PURPOSE:To accomplish calibration in which a ground level is taken as a reference and to enhance the accuracy of the calibration by performing the calibration of a surface potential detection means at a position here the means in opposed to a ground part in the specified area of a photosensitive body. CONSTITUTION:The photosensitive body 34A and the ground part 54 are formed on the surface of photosnesitive drum 34 and the ground part 54 is grounded through a shaft 52. When the ground part 54 comes to a position where it is opposed to the surface potential sensor 32, a photosensor 60 detects the notch 59 of a disk 58 fixed to the shaft 52. When the sensor 60 detects the notch 59 by rotating the drum 34, the calibration of the sensor 32 is started, and the calibration of the sensor 32 is performed in a state where the ground level, that means, OV is taken as the reference. Then, the surface potential of the photosensitive body 34A is detected by the sensor 32 and an electrostatic charging voltage is corrected based on the detected value. |
