| 摘要 |
PROBLEM TO BE SOLVED: To realize an optical scanner at a low cost which exactly detects the position of the main scanning direction of each laser beam, and then corrects the starting position of image writing while stably acquiring a synchronous detection signal, when performing the simultaneous scanning of a plurality of scanning lines with a plurality of laser beams. SOLUTION: When an incidence on an SOS sensor 36 is performed only by either of two laser beams, the gain (amplifiers 102A, 102B) of the SOS sensor 36 is set as a high gain with a gain setting signal. Besides, when both two laser beams are made incident on the SOS sensor 36, the gain of the SOS sensor 36 is set as a low gain. Thus, by changing the gain of the SOS sensor 36, an SOS signal can be detected stably in both cases of only one or two laser beams made incident on the SOS sensor 36. Thereby, the position of the main scanning direction of each laser beam can be detected exactly, and the starting position of image writing can be corrected.
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