Patent ID: 7304778

Claim:
An optical scanning system, comprising: light source means; an optical deflector having a deflecting surface, for scanningly deflecting a light beam emitted from said light source means; and an imaging optical system for imaging the light beam, deflected by said deflecting surface of said optical deflector, upon a scan surface to be scanned; wherein, when γ (γ≠0) refers to an angle which is defined, in a sub-scan sectional plane, between a principal ray of the light beam from said light source means and a normal to said deflecting surface of said optical deflector as the light beam is going to be incident on said deflecting surface, β refers to an imaging magnification of said imaging optical system with respect to a sub-scan direction, W [mm] refers to a light-beam width, in a main-scan direction, of a light beam that passes a light exit surface of an imaging optical element, of said imaging optical system, which element is closest to the scan surface, and ε (ε≠γ) refers to an angle defined, in the sub-scan sectional plane, between an optical axis of said imaging optical system and a straight line that connects a point of deflection of the light beam incident on said deflecting surface of said optical deflector and an imaging point of the light beam being imaged on the scan surface, a relation 1 + β β ×  tan ⁡ ( γ - ɛ )  × W ≤ 0.15 ⁢ [ mm ] is satisfied.