To obtain a recognition method whose measuring accuracy is high by a method wherein, in an electrifying, exposure and reelectrifying process, the surface potential of a photosensitive drum which is reelectrified by an electrification means is adjusted so as to be lower than the surface potential of a photoreceptor drum which is electrified by the electrification means.
The surface of a photoreceptor drum 1 is first electrified by an electrifier 2. Then, a part in which a surface potential is to be measured is exposed, and the surface of the photosensitive drum 1 including an exposed region is reelectrified in the second round of the photosensitive drum 1 without performing a developing operation, a transfer operation, a cleaning operation and an electricity removal operation. In this case, the surface potential of the reelectrified photosensitive drum is adjusted so as to be lower than the surface potential of the first electrified photosensitive drum. Thereby, even when a potential is dropped due to dark attenuation in an unexposed region, the surface potential of the reelectrified photosensitive drum is controlled so as to be low, a current which flows to the unexposed region at a time when the photosensitive drum is reelectrified is suppressed, and the measuring accuracy of a recognition method is made high.
YAMANE SHINJI
KAJIKAWA CHIKAYUKI
