SCANNING OPTICAL SYSTEM, OPTICAL SCANNER AND IMAGE FORMING DEVICE

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. The lens 7 positioned on the surface to be scanned side is provided with negative refractive power in the main scanning direction and positive refractive power in the sub-scanning direction. At least one lens surface of the lens 6 within a main scanning cross section is formed so that it is not a circular arc. Besides, at least one lens surface of the lens 7 within the main scanning cross section is formed so that it is not a circular arc. The radius of curvature is different in the main scanning direction and in the sub-scanning direction at least on one lens surface of the lens 6. Besides, the radius of curvature is different in the main scanning direction and in the sub-scanning direction at least on one lens surface of the lens 7.