| 摘要 |
PROBLEM TO BE SOLVED: To obtain a stable excellent light spot by excellently compensating wave aberration on a pupil together with the curvature of an image plane or optical magnification in a scanning image-formation optical system. SOLUTION: In this device, one or more beams from a light source 1 side are deflected by a light deflecting means 4 and the deflected beams are condensed as the light spots on a surface to be scanned 7 by the scanning image- formation optical systems 5 and 6, and the surface to be scanned is optically scanned. The systems 5 and 6 are composed of one or more optical elements including lenses, and at least one surface of the lenses included in the systems 5 and 6 is a sub-non circular-arc surface where the shape of a main scanning surface is a circular-arc or a non circular-arc and the shape of a subscanning surface is a non circular-arc, and the sub-non circular-arc surface is formed on the lens where the diameter of the deflected beams transmitted through the systems 5 and 6 is the largest on the subscanning surface.
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