| 摘要 |
PROBLEM TO BE SOLVED: To reduce color variation in a gray scale of an exposed image due to speed variation of a photosensitive head corresponding to a pitch of teeth of a belt with teeth. SOLUTION: Light emitting dots in a dot block 14a on a photosensitive head 14 are arranged in a staggered fashion such that an odd row A consisting of odd numbers of the light emitting dots and an even row B consisting of even numbers of the light emitting dots are arranged with a distance Ds. A last transmission system consists of a pulley 7 with teeth at a driving side which is driven by an output shaft 6a of a motor 6, a pulley 9 with teeth at a following side and a belt 8 with teeth. One part of the belt 8 is fixed to a base 13. The dot block 14a on the photosensitive head 14 moves in a speed the same as the speed of the belt 8 so that variation of the speed having a cycle the same as a pitch P of the teeth of the belt 8 is generated. In order to prevent color variation in a gray scale of an exposed image corresponding to the variation of the speed, the pitch P of the teeth of the belt 8 is determined based on the expression of '2Ds/(2n+1)' (n is 0 or a positive integer number).
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