| 摘要 |
A multi-beam laser exposure unit of the present invention includes a light beam deflector for deflecting a light beam in a predetermined direction, a plurality of laser devices, a pre-optical system, including a glass lens and a plastic lens, for converting a cross sectional shape a of light beam emitted from the respective laser devices to a predetermined shape, and a post-deflection optical system, including two lenses for image-forming each light beam deflected by the deflector to be scanned on a predetermined image surface at a uniform speed. The power of the two lenses of the post-deflection optical system is defined to be positive in a direction parallel to a rotational axis of reflective surfaces of the deflector. Also, at least one lens surface of these lenses is formed not to include a rotational symmetrical surface.
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