| 摘要 |
PURPOSE:To eliminate change in detection value resulting from a difference in detecting position by making a sensor for detecting the concentration or potential of toner on a photosensitive drum always detect the value in the specific position on the photosensitive drum or that corresponding to one rotation of its periphery. CONSTITUTION:When the rotating reference position 20 on the side of the photosensitive drum 1 is detected by a position detecting sensor 19, an optical mechanism carries out scanning and the formation of an electrostatic latent image on the photosensitive drum 1 is started. When the preset length of time elapses after the detection of the rotating reference position 20 by means of the position detecting sensor 19, the detection of toner concentration or potential is carried out for the fixed length of time by the concentration sensor 4 disposed near and opposite that, on the photosensitive drum 1. |
