| 摘要 |
PURPOSE:To produce an accurate synchronizing signal, by storing previously the size of the signal which is immediately preceding by one time to control the gain that is used when the present signal is amplified in case the synchronizing signal is periodically supplied. CONSTITUTION:A laser printer of rotary polyhedral mirror scanning type has a reflector set at the edge of a photosensitive drum and utilizes the reflected light of the drum as a synchronizing signal. The amplitude of the gain detected by a photodiode 7 is set constant by an amplifier 16 having controlled gain and then sliced to be turned into a pulse converting output. While the output signal of the diode 7 is digitized by an A/D converter 11 and stored in a storage circuit 12. This stored signal is read out when a new output signal is produced from the diode 7 and then converted into an analog signal. Then the gain of the amplifier 16 is controlled. |
