Patent ID: 7710446

Claim:
A light scanning unit comprising: a light source to generate and irradiate at least one beam corresponding to an image signal; a beam deflector to deflect and scan the beam irradiated by the light source; and an f-θ lens to form an image from the beam deflected by the beam deflector onto a surface to be scanned, wherein the f-θ lens is a single lens wherein the entire f-θ lens forming the image from the beam deflected by the beam deflector has a shape that satisfies the following equation (2): - 0.2 < SAG ⁢ ⁢ 1 + SAG ⁢ ⁢ 2 d 2 < 0.2 ( 2 ) where SAG 1 is the Z value of an incident surface of the f-θ lens, SAG 2 is the Z value of an exit surface of the f-θ lens, based on an XYZ coordinate system in which a main scanning plane is a Y-Z plane and a sub-scanning plane is an X-Z plane, and d 2 is a center thickness of the f-θ lens.