| 摘要 |
PURPOSE:To stabilize always detection of the surface potential of a photosensitive body by providing a means which shields a potential detecting electrode facing the photosensitive body and measuring an induced potential generated in the potential detecting electrode in the state where shielding is released. CONSTITUTION:Before the start of measurement, a potential detecting electrode 7 is shielded by a hollow cylinder 8, and a relay 13 is closed. At the measurement start time, the hollow cylinder 8 is rotated, and the relay 13 is opened just before an aperture part 10 of this cylinder 10 faces a photosensitive drum 5. The induced potential generated in the potential detecting electrode 7 is measured to detect the surface potential of the photosensitive drum 5. After one measurement is terminated in this manner, the hollow cylinder 8 is returned to the state before the start of measurement, and the relay 13 is closed, and they are held until measurement is started again. Hereafter, the similar operation is repeated. Thus, the time of one measurement is shortened to several seconds or shorter, and the attenuation quantity of voltage due to attenuation characteristic is held down to a small value, and the surface potential of the photosensitive body is always measured stably. |
