| 摘要 |
PROBLEM TO BE SOLVED: To suppress the fluctuation of the beam diameter of a light beam and the fluctuation of the light quantity distribution without complicating the structure. SOLUTION: The direction of an LD 16 is adjusted so that the optical axis L<1> of the light beam may be slightly inclined to a side close to an fθlens 14 as compared with the conventional optical axis L<0> , and in the case the reflection surface of a rotary polygon mirror 12 faces so that the incident light beam may be reflected to a side close to the optical path of the aforesaid light beam, the boundary of an irradiation range of the light beam shown by a dotted circular mark is positioned on the reflection surface of the rotary polygon mirror 12, and a part of the reflection surface along a main scanning direction is not irradiated with the light beam. In the case the reflection surface faces so that the incident light beam may be reflected to the center in a deflection extent, or in the case the reflection surface faces so that the incident light beam may be reflected to a side opposite to the side close to the optical path of the incident light beam, the light beam is made incident on the whole range of the reflection surface along the main scanning direction, so that the width of the light beam emitted from the rotary polygon mirror is almost fixed. |
