Patent ID: 7245411

Claim:
An optical scanning apparatus to project a ray of light from a light source towards a predetermined direction and to converge the ray of light on a photosensitive medium, the optical scanning apparatus comprising: a collimating lens to transform the ray of light from the light source into parallel rays and provided of a single plastic lens that has a refraction surface provided on one side and a diffraction surface provided on an opposite side, where a power of the diffraction surface is larger than a power of the refraction surface; a cylindrical lens to converge a light component from the collimating lens, in a sub-scanning direction into a linear ray of light in a main-scanning direction; a light deflector to deflect the linear ray from the cylindrical lens; and an f-θ lens to converge the reflected ray of light from the light deflector onto the photosensitive medium, wherein the refraction surface and the diffraction surface have powers to satisfy the condition of: - 3 ≤ K d K r ≤ - 2 where, K d is the power of the diffraction surface, and K r is the power of the refraction surface.