| 摘要 |
PROBLEM TO BE SOLVED: To provide a scanning lens which has a function to correct curvature of field in both horizontal and vertical scanning directions with one lens surface and can be shaped to have an axis of rotation facilitating the formation of the surface. SOLUTION: An fθlens 20 is constituted by arraying a 1st lens 21 and a 2nd lens 22 in order from a polygon mirror 4 to a drawing plane 5. At least the lens surface 21a of the 1st lens 21 on the side of the polygon 4 is a deformed toric surface defined as the track formed by rotating at least a nonarcuate curve in a horizontal scanning surface on an axis of rotation crossing the optical axis at a right angle in a main scanning surface, and has negative power in the vertical scanning direction. The surface 22a of the 2nd lens 22 on the side of the polygon mirror 4 is a cylindrical surface which has negative power only in the vertical scanning direction and the surface 22b on the side of the driving surface 5 is a toric surface which has positive power in the both horizontal and vertical scanning direction. |
