| 摘要 |
PROBLEM TO BE SOLVED: To eliminate a windage loss caused by the rotation of a polyhedric mirror based on the shape of the mirror. SOLUTION: Reflection gratings 31a are formed on the deflective side face of a cylindrical body 31 at plural cycles, and a distance is set so that the grating pitch per cycle may counterbalance the power of the cylinder surface in accordance with the light incident angle of the light deflector, and the cylindrical body 31 is made to function as a deflecting element equipped with a deflection surface equivalent to the conventional polyhedric mirror, and each lens power of fθlenses 36 and 37 is adjusted so as to have the conjugate relation in a subscanning direction as for the reflection gratings 31a and a photoreceptor 38, then, the deviation of the image forming point on the photoreceptor 38 is optically counterbalanced.
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