| 摘要 |
To achieve strong-illumination and weak-illumination of a laser beam onto a photo-sensitive drum, a laser control device controls an LD drive current switching circuit to switch between drive currents generated by an LD-bright-lighting current drive control circuit and drive currents generated by an LD-dim-lighting current drive control circuit, and applies the selected drive currents to a semiconductor laser element. The laser beam from the semiconductor laser element is detected by a photodiode, and the drive current is adjusted by feedback control based on the detected optical intensity. Since a detection signal from the photodiode is amplified not only when the laser beam is illuminating strongly but also when the laser beam is illuminating weakly, even tiny variations in the optical intensity during weak illumination can be detected clearly and can be reflected in feedback control. Thus, the laser control device feeds back the optical intensity of the laser beam to ensure that the optical intensity of the laser beam is kept constant.
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