Patent ID: 7085031

Claim:
An optical scanner comprising: a light source that emits a light beam; a light deflector on which the light beam impinges; an incident optical system that allows the light beam to impinge on the light deflector such that the width of the light beam incident on the light deflector in the main scanning direction is larger than the width of each deflecting surface of the light deflector in the main scanning direction; and a focusing optical system that guides the light beam deflected by the light deflector to a surface to be scanned, wherein one or more optical surfaces having a non-arc shape in a main scanning cross-section are provided in at least either the incident optical system or the focusing optical system such that a first direction of aberration is opposite to a second direction of aberration, the first direction being the direction of the phase difference in wavefront aberration in the main scanning direction between the chief ray of the light beam and the marginal rays of the light beam, the phase difference occurring when the light beam incident on the surface to be scanned at the maximum image height passes through the incident optical system, the second direction being the direction of another phase difference in wavefront aberration in the main scanning direction between the chief ray of the light beam and the marginal rays of the light beam, the phase difference occurring when the light beam incident on the surface to be scanned at the maximum image height passes through the focusing optical system.