| 摘要 |
PROBLEM TO BE SOLVED: To suppress the deterioration of an image quality by normally stably rotating a rotary polygon mirror while attaining the miniaturization of an apparatus by suppressing the increase of the number of parts. SOLUTION: Two rotary polygon mirrors 22 and 24 on upper and lower sides are coaxially arranged, and the mirror on the lower side out of them deflects light beams AM and AC and performs scanning with them as an under- field optical system, and the mirror on the upper side deflects light beams AY and AK and performs scanning with them as an over-field optical system. Two fθlenses 26B and 28B by which image formation is performed with the light beams AM and AC at photoreceptive drums 32M and 32C arranged inside are made as image formation optical systems whose focal distances are shorter than those of fθlenses 26A and 28A by which image formation is performed with the light beams AY and AK at photoreceptive drums 32Y and 32K arranged outside. COPYRIGHT: (C)2003,JPO
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