| 摘要 |
PROBLEM TO BE SOLVED: To adjust image write-starting positions to be the same in a simple constitution when images of a plurality of lines are to be formed with the use of a plurality of laser lights. SOLUTION: When a scan start position of a first laser light is at the lower side in a main scan direction than a scan start position of a second laser light and, a shift width dh in the main scan direction of the first laser light and second laser light is shorter than a breadth D of an incidence face of a synchronous detection sensor, only the first laser light is scanned once (S1) and an output time of pulse signals at the time is obtained as a reference timeΔt1 (S2). Then, the first laser light and second laser light are scanned once at the same time (S3), and the output time of the pulse signals is obtained as a time to be comparedΔt2 (S4). A difference of the reference timeΔt1 and the time to be comparedΔt2 is obtained and set as a correction valueΔt to regulate an image write timing by each laser light (S5).
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