| 摘要 |
PROBLEM TO BE SOLVED: To eliminate jitter generated by mirror contamination or the like by comparing a response time difference measured by a beam detector(BD) sensor with a natural time difference of the BD sensor, calculating a time difference deviation and adjusting an image write position based on the calculated value. SOLUTION: When mirror contamination is brought about in a rise edge part which executes BD detection to a first laser light, a width t1 becomes smaller than at a normal time. For correcting this, a CPU reads each BD pulse width of the first laser light and a second laser light by an AD converter, and calculates a missing partΔt1 (=t2-t1) of t1. A lighting timing of the first laser light is delayed by a time ofΔt1+t1+tb from a lighting timing of the second laser light. An exposure position in a main scanning direction on a surface of a photosensitive drum is thus registered. The correction to write positions of a laser light 1 and a laser light 2 can eliminate BD jitter caused by a variation of the BD pulse width.
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