| 摘要 |
PROBLEM TO BE SOLVED: To provide the synchronizing signal generating circuit of an optical scanner capable of highly precisely detecting synchronizing signals corresponding to respective beam lights with a single photodetector in an optical scanner scanning plural beam lights. SOLUTION: An optical scanner is constituted of a light source part provided with four laser light sources, a rotary polygon mirror, an fθlens, a photosensitive drum 8 and a synchronizing signal generating circuit, etc. The synchronizing signal generating circuit is constituted of a photodiode 6 and a signal processing circuit. Then, the width L in the main scanning direction of the effective light receiving area of the photodiode 6 is set so as to satisfy an inequality, L<=P-W/4, with respect to the interval between adjacent laser beams in the main scanning direction and the diameter W of laser beams in the main scanning direction.
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