| 摘要 |
PROBLEM TO BE SOLVED: To improve accuracy in superposition of respective color images by suppressing an increase in control error even under an environment of large temperature variation in an image forming device. SOLUTION: A phase difference is obtained between binary signals resulting from detecting marks 5 on a belt 1 by two mark detection means A and B. An ambient temperature of a holding member 6 for the mark detection means is measured, and temperature variation is measured. The amount of phase difference measurement error caused by thermal expansion of the holding member 6 is calculated from the temperature variation, a linear expansion coefficient of the holding member 6, the distance between the mark detection means, and a target speed. A result of pulse cycle measurement is corrected based on an initial value of the phase difference and the measured phase difference. The amount of phase difference measurement error is used to further correct the corrected result of pulse cycle measurement. Speed and position are controlled using a control signal based on the corrected result of pulse cycle measurement. COPYRIGHT: (C)2008,JPO&INPIT
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