| 摘要 |
PROBLEM TO BE SOLVED: To eliminate the phenomenon that a beam shape becomes a triangle on both ends of an image area and to obtain a uniform-shaped small-diameter beam in a whole image area by specifying the shape in the main scan direction of an anamorphic surface in the whole image area and perpendicularly or almost perpendicularly making incident laser light on all anamorphic surfaces. SOLUTION: A scan lens system contains the anamorphic surface that power in the main scan direction being the deflective direction of laser beams 2 is different from the power in the sub-scan direction orthogonally intersecting with the main scan direction, and the shapes in the main scan direction of these anamorphic surfaces S5, S6 are satisfied with the relation of 0.995<|Vr.Vs|<=1 in the whole effective image area of surface. Where, Vr is the directional vector of main light made incident on the anamorphic surface, and Vs is the normal vector the anamorphic surface on an incident position of the main light made incident on the anamorphic surface. Thus, the laser beams 2 are made incident perpendicularly or almost perpendicularly on the anamorphic surfaces S5, S6.
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