Optical scanner, image forming apparatus and image reading apparatus

摘要

An optical scanner comprising a light source unit, an optical deflector to scan a light beam from the light source unit, a first image formation optical system disposed between the light source unit and the optical deflector, and a second image formation optical system disposed between the optical deflector and the surface to be scanned, wherein the second image formation optical system comprises a first curved mirror to reflect the light beam from the optical deflector and a second curved mirror to focus the light beam from the first curved mirror on the surface to be scanned, having surface shapes of any of the group consisting of the first curved mirror having a toric surface with a convex shape in the main scanning direction, which is the direction a light beam is scanned in, and with a concave shape in the sub scanning direction, which is the direction perpendicular to the main scanning direction, and the first curved mirror having a toric surface with a concave shape in the main scanning direction and a convex shape in the sub scanning direction and a second curved mirror having a toric surface or cylindrical surface without a refractive power or with a concave shape in the main scanning direction, and with a concave shape in the sub scanning direction to focus the light beam from the first curved mirror on the surface to be scanned.