| 摘要 |
PURPOSE:To prevent a photosensitive drum from partial deterioration by providing the titled device with plural optical sensors receiving optical beams successively in accordance with the scanning of optical beams and outputting a signal from a different sensor in each completion of picture formation. CONSTITUTION:Light projected from a light emitting body 2 is reflected by a mirror 4 and a detecting mirror 20 through an optical path 5a and reaches photodetective sensors 7a, 7b respectively. The detection signals of the sensors 7a, 7b are simultaneously sent to a switching circuit 18, which selects only the detection signal from the sensor 7a and outputs the selected signal to a control circuit 19. After passing a fixed short time, the circuit 19 starts to apply a picture signal to the light emitting body 2 and the starting position of the formation of the preceding picture is determined in each completion of the formation of one picture. Subsequently, the circuit 19 starts to apply a picture signal to the light emitting body 2 after passing said fixed time from the reception of the detection signal of the sensor 7b. Since the positions of both sensors are shifted by a distance (l) in the parallel direction with a picture scanning line 6, the picture formation starting positions are also shifted by (l) in the scanning direction of the optical beams. |
