Patent ID: 6392773
Filing Date: 2002-05-21
Classification: B41J,G02B,H04N

Abstract:
A multi-beam scanning optical system, comprising:a light source unit emitting a plurality of light beams, said plurality of beams being parallel to each other; a polygonal mirror having a plurality of reflection surfaces arranged along a rotational direction of said polygonal mirror, the plurality of beams emitted by said light source unit being incident on said polygonal mirror and reflected by the reflection surfaces of said polygonal mirror; and an f&thgr; lens system, the plurality of beams reflected by the reflection surface of said polygonal mirror passing through said f&thgr; lens system and proceeding toward surfaces to be scanned, wherein said f&thgr; lens includes a first lens, a second lens and a third lens, said plurality of beams deflected by said polygonal mirror being incident on said first, second and third lenses in this order, wherein said first lens consists of a first lens element and second lens element, said plurality of beams being incident on said first and second lens elements in this order, said first lens element converging said plurality of beams in an auxiliary scanning direction, said second lens element converging said plurality of beams in a main scanning direction, and wherein a plurality of convex surfaces corresponding to said plurality of beams are formed on one of surfaces of said first and second lens elements, said plurality of convex surfaces extending in the main scanning direction, said plurality of convex surfaces converging said plurality of beams in the auxiliary scanning direction, respectively, a diffraction lens structure for compensating for lateral chromatic aberration caused by a refraction lens structure of said f&thgr; lens system being formed on each of said plurality of convex surfaces.