Beam scanning apparatus

摘要

A beam scanning apparatus having a collimating lens in which a beam emitted from a light source is transformed into at least one of a convergent beam and a parallel beam with respect to an optical axis and outputted towards a slit. The collimating lens being one sheet of a spherical surface lens satisfying the relationship: 1 $-0.3<\frac{\mathrm{R2}}{\mathrm{R1}}<-0.1$ $0.05<\frac{d}{f}<0.5$ in which, R1 denotes a curvature radius of a first surface of the collimating lens opposing the light source, R2 denotes a curvature radius of a second surface of the collimating lens opposing the slit, d denotes a center thickness of the collimating lens, and f denotes a focal length from the collimating lens to the light source. By virtue of the structure of the beam scanning apparatus using the collimating lens, deteriorating printing quality due to temperature change is prevented and cost can be saved.