| 摘要 |
PROBLEM TO BE SOLVED: To arrange the position of a scanning line with respect to each photoreceptor drum to be constant even when a heating condition is different between a housing in which a scanning optical system is housed and a drum support in which a photoreceptor drum is housed. SOLUTION: When temperature rises and the housings 10 and 20 are expanded, mirrors 235 and 336 are moved in the same direction as the movement of 3rd lenses 233 and 333 outward by an amount larger than the moving amount of the lenses 233 and 333 by the action of an adjusting plate. Since the lenses 233 and 333 have positive power in a subscanning direction, emitted light is deflected toward the inside if the center axis of incident light is decentered to the outside with respect to the optical axis. By setting the expansion coefficient and the size of the adjusting plate so that the movement of the scanning line by the above deflection and the movement of the scanning line by the difference of expansion amount between the housings 10 and 20 and a drum supporting base 30 are negated each other, the position of a scanning line is arranged to be constant regardless of temperature change.
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