Optical scanning apparatus and image forming apparatus

Abstract

An optical scanning apparatus includes a semiconductor laser, a coupling lens, a polygon mirror, a motor, an optical scanning system including a first scanning lens with an optical surface, a housing, a cover, and a partition with an opening closed with the first scanning lens. Shifting amounts of a focus position of a beam with respect to a reference imaging plane in a main scanning direction are in relations ΔA<0 and ΔA<ΔB<ΔC, where ΔA mm and ΔB mm are shifting amounts when the semiconductor laser, the coupling lens, and the optical scanning system are at a normal ambient temperature and at an upper-limit ambient temperature, respectively, and ΔC mm is a shifting amount when the semiconductor laser and the coupling lens are at the normal ambient temperature and the first scanning lens is at a first temperature.