Patent ID: 8564635

Claim:
An optical scanner comprising: a light source including a plurality of light emitters; an aperture member that collimates light beams output from the light source; a deflector that defects the light beams passing through the aperture member; a scanning optical system that condenses the light beams deflected by the deflector onto a surface to be scanned so as to optically scan the surface in a main-scanning direction; and a lens placed between the aperture member and the deflector, the lens having refraction power in a sub-scanning direction perpendicular to the main-scanning direction, wherein the scanning optical system includes a resin scanning system having at least one resin scanning lens, at least one folding mirror or one sheet glass is disposed between a scanning lens nearest to the deflector in the resin scanning system and the scanned surface, at least one scanning lens included in the resin scanning system has an uneven birefringence distribution with respect to the sub-scanning direction, and the refraction power in the sub-scanning direction of the lens and a length of a light path between the lens and the scanning lens nearest to the deflector in the resin scanning system are configured in combination such that an optical conjugate image of the aperture member is formed between a lens surface nearest to the deflector in the resin scanning system and a lens surface nearest to the scanned surface with respect to the sub-scanning direction.