OPTICAL SCANNING DEVICE AND IMAGE FORMING APPARATUS

摘要

An optical scanning device that scans a scanning surface with a light beam includes a light source that emits the light beam and a pre-deflector optical system that includes at least one diffractive optical element including a diffraction surface having no power at room temperature. The diffraction surface has a multi-step shape having a plurality of zone surfaces substantially perpendicular to an optical axis and a plurality of step surfaces each adjacent to each of the zone surfaces. On a cross sectional plane of the diffraction surface including the optical axis, each of the zone surfaces and each of the step surfaces makes an obtuse angle.