| 摘要 |
There is provided a scanning optical system which includes an imaging optical system having a first plastic lens and a second plastic lens. With regard to an auxiliary scanning direction, the first plastic lens is configured such that origin points of surfaces thereof are located on opposite sides of a principal axis, an amount of shifting of each of the origin points of the surfaces with respect to the principal axis is less than half of a diameter of mirror-finished area of corresponding one of the surfaces thereof, and both of centers of curvature of the surfaces thereof on the respective origin points are positioned on the light source side of the first plastic lens. The second plastic lens is configured such that at least one of surfaces thereof has an anamorphic aspherical surface, at least one of origin points of the surfaces thereof being located on the same side of the principal axis as the origin point of a rear surface of the first plastic lens in the auxiliary scanning direction, an amount of shifting of each of the origin points thereof with respect to the principal axis being less than half of a diameter of mirror-finished area of corresponding one of the surfaces thereof in the auxiliary scanning direction.
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