| 摘要 |
PROBLEM TO BE SOLVED: To improve the signal processing precision of a BD signal by discriminating horizontal synchronizing (BD) signals corresponding to light sources from plural horizontal synchronizing signals becoming the reference of image formation in a main scanning direction, which correspond to the plural light sources. SOLUTION: /LON 1 and 2 signals generated from a laser control signal generation circuit 804 are signals for compulsorily emitting lasers L1 and L2. They are activated at timing when /BD 1 and 2 signals are generated in a non-image area and the lasers L1 and L2 are compulsorily emitted. ON/OFF of the lasers L1 and L2 are controlled by a laser driver 805. The /BD 1 signal and the /BD 2 signal, which are detected by a BVD sensor 803, are transmitted to a video controller 600 as one /BD signal. While a scanner motor 609 is regularly rotated, timing when the /BD 2 signal is generated after the /BD 1 signal is generated is after constant time and therefore the /BD 1 and 2 signals can be discriminated in comparison with a period which is previously measured.
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