Patent ID: 8441512

Claim:
An optical scanner comprising: a light source including a plurality of light-emitting elements; a deflector that deflects a light beam output from the light source; and a scanning optical system that condenses the light beam deflected by the deflector onto one target surface, and includes a first optical system composed of at least one resin scanning lens, and a second optical system disposed between the one target surface and one resin scanning lens located nearest to the deflector in the first optical system and including a plurality of optical elements composed of at least either one of a folding mirror(s) and a glass sheet(s), wherein m1+g2=m2+g1 is satisfied concerning lengths of optical paths of a first ray and a second ray each included in a light beam being incident on the second optical system and being separated from each other in a rotating shaft direction of the deflector, both the first ray and the second ray being destined to the one target surface, and the lengths of the optical paths being between the deflector and the respective optical elements included in the second optical system on a plane perpendicular to a main-scanning direction, where m1 is number of the folding mirror(s) to which the first ray has a shorter optical path than the second ray does, m2 is number of the folding mirror(s) to which the first ray has a longer optical path than the second ray does, g1 is number of the glass sheet(s) to which the first ray has a shorter optical path than the second ray does, and g2 is number of the glass sheet(s) to which the first ray has a longer optical path than the second ray does.