Patent ID: 8203774

Claim:
An optical scanning device, comprising: a light source for emitting a light beam; a deflector having a plurality of flat reflecting surfaces; a first optical system disposed between the light source and the deflector; and a second optical system disposed between the deflector and a photoreceptor surface, and configured such that the reflecting surfaces of the deflector and the photoreceptor surface are conjugated in a sub-scanning direction at every deflection angle in a main-scanning range; wherein the light beam traveling from the first optical system to the deflector has a width greater than a dimension in a main-scanning direction of each reflecting surface of the deflector, and wherein the light beam passes through different portions of the first optical system depending on whether the light beam is to be deflected by the deflector to be directed to an edge portion of the main-scanning range or to be directed to a center portion of the main-scanning range such that the light beam traveling to the deflector has a smaller average wavefront curvature in a sub-scanning direction when the light beam is to be deflected by the deflector to be directed to an edge portion of the main-scanning range than when the light beam is to be deflected by the deflector to be directed to the center portion of the main-scanning range.