Optical scanning unit

摘要

An optical scanning unit including: a light source which produces and emits a beam; a beam deflector which deflects and scans the beam in a main scanning direction of an exposed object; and an f-theta lens which corrects the beam deflected by the beam deflector at different magnifications for the main scanning direction than for a subscanning direction so that a corrected beam is focused onto the exposed object. When H is an entire length in the main scanning direction of the beam focused onto the exposed object and L is an axial distance between a reflection face of the beam deflector and the exposed object, the relationship of H and L satisfies an expression $0.25<=\frac{H}{2.L}<=1.75.$