| 摘要 |
PROBLEM TO BE SOLVED: To realize a scanning optical system capable of forming a small-diameter light spot while securing back length regardless of a single beam system or a multibeam system. SOLUTION: This scanning optical system is constituted so that beams deflected by a light deflector 5 are condensed on a surface to be scanned 9 as the light spot. Then, it is constituted of two lenses 6 and 7. The lens 6 positioned on the light deflector side is provided with positive refractive power in a main scanning direction and negative refractive power in a sub-scanning direction. Besides, the shape thereof within a main scanning cross section is the meniscus lens whose concave surface faces the light deflector side and at least one lens surface thereof within the main scanning cross section is formed so that it is not a circular arc. Moreover, the radius of curvature is different in the main scanning direction and in the sub-scanning direction at least on one lens surface thereof. The lens 7 positioned on the surface to be scanned side is provided with positive refractive power in the main scanning direction and positive refractive power in the sub-scanning direction. Besides, at least one lens surface thereof within the main scanning cross section is formed so that it is not a circular arc and the radius of curvature is different in the main scanning direction and in the sub-scanning direction at least on one lens surface thereof. |
