| 摘要 |
In a main-scanning direction, light incident on a resonance mirror is convergent light and a first lens of a second optical system has a negative refractive power. Consequently, even with a small angle of deflection, the distance from the resonance mirror to a photoconductor required for obtaining a desired scanning width in the main-scanning direction can be reduced. Moreover, in a sub-scanning direction, light incident on the resonance mirror is parallel light, and the first lens of the second optical system has a negative refractive power and a second lens thereof has a positive refractive power. In addition, the first lens has both surfaces formed with a free curved surface and the second lens thereof also has a free curved surface. This permits keeping the sub-scanning magnification uniform, thus avoiding, even in high-speed drawing with a plurality of beams, image quality deterioration due a change in an interval in the sub-scanning direction between the plurality of beams.
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