PURPOSE: To provide a method of measuring the photosensitive characteristic of a photoreceptor drum, that is, the potential unevenness of the drum surface caused by the defect of the photoreceptor drum itself or caused by the defect of a grid provided as occasion calls, correctly as well as nondestructively in a short time.
CONSTITUTION: A potential sensor 27 is reciprocated over a zero potential calibrator 28 and the whole effective charged area of a photoreceptor drum 2, and the photoreceptor drum 2 is rotated at least by one circle respectively at the going and returning time of the sensor 27 in the effective charged area. The dark potential of the photoreceptor drum surface charged at the going time of the sensor 27 after zero potential calibration, and the light potential of the photoreceptor drum surface exposed at the returning time of the sensor 27 are respectively measured every step of micro-moving quantity of the sensor 27.
UEHARA SOICHI
MATSUI NAOHISA
