Patent ID: 7265774

Claim:
A beam scanning apparatus, comprising 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: - 0.3 < R2 R1 < - 0.1 0.05 < d f < 0.5 in which, R 1 denotes a curvature radius of a first surface of the collimating lens opposing the light source and having a first positive constant refractive index, R 2 denotes a curvature radius of a second surface of the collimating lens opposing the slit and having a second positive constant refractive index, d denotes a center thickness of the collimating lens, and f denotes a focal length from the collimating lens to the light source, wherein the collimating lens is glass, and wherein a magnification ratio in a main scanning direction and a magnification in a sub scanning direction are substantially the same.