| 摘要 |
PURPOSE:To prevent the continuous formation of toner images on the same circumference of a photosensitive drum over a long period by providing the titled device with a means to delay a detecting signal and a means to select the delay means and selecting and using the delay means properly. CONSTITUTION:When a selection signal generating part 9 generates ''1'', an OR circuit 13 outputs the output signal of a photodiode 6 as it is, and after passing the time (t) from the rising part of the output signal, a laser beam is modulated. When the generating part 9 output ''0'', the circuit 13 outputs a signal obtained by inverting the output signal of the photodiode 6, and after passing the time (t) from the falling edge part of the output signal, a laser beam is modulated. Namely, the selection of the output signal of an NOT circuit 8 by the selection means delays the modulation starting time of the laser beam by time tau as compared to the selection of the output signal of the photodiode 6. Consequently, proper generation of a signal ''1'' or ''0'' from the generating part 9 makes it possible to prevent the continuous formation of toner images on the same circumference of the photosensitive drum over a long period. |
