Scanning optical system

A scanning optical system in which a bundle of rays emitted from a light source scans a surface to be scanned through an optical deflector and an image forming optical system, said image forming optical system comprising:

• a positive front lens group comprising two lens elements;
• and
• a rear lens group comprising an elongated single anamorphic lens element positioned in the vicinity of said surface to be scanned and having a positive refractive power in a sub scanning direction;
• wherein all of said lens elements in the image forming optical system are made of a resin material, and
• wherein said scanning optical system satisfies the following conditions:
• d.sub.0 /f<0.23
• 0.70<f/f.sub.1 <1.30
• d.sub.fB /f<0.50
• wherein
• f designates the focal length of said image forming optical system in a main scanning direction;
• f.sub.1 designates the focal length of the first lens element of said front lens group;
• d.sub.0 designates the distance from the intersecting point of a central axis of said bundle of rays being emitted from said light source and incident on said optical deflector and an optical axis of said image forming optical system to the first lens surface, on the side of said optical deflector, of said image forming optical system;
• and
• d.sub.fB designates the distance between said photoconductive surface and the last lens surface, closest to said surface to be scanned, of said rear lens group.