| 摘要 |
PROBLEM TO BE SOLVED: To register write positions of color component images even when a rotational speed of a photosensitive body or the like shifts due to influence of a load change, a backlash of a drive transmission gear or the like. SOLUTION: A phase difference-detecting circuit 122 detects and holes a phase difference between an ITOP signal and a BD signal with a predetermined timing, and detects the phase difference between the ITOP signal and BD signal every time a color component image is formed. The detecting circuit compares the phase difference detected with the predetermined timing and the phase difference detected for every formation of the color component image. An image write timing control circuit 101 changes on the basis of the comparison result the number of BD signals counted before the image is started to be formed after the ITOP signal is generated, thereby controlling an image formation start timing.
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