Patent ID: 8675034

Claim:
An optical scanning apparatus comprising: a light source that has a plurality of light emitting points; a light deflecting unit that deflects a plurality of light fluxes emitted from the light source for scanning; a before-light-deflecting-unit optical system that shapes the plurality of light fluxes emitted from the light source to form a linear image which is elongated in a deflection scanning direction at an approximate position of a deflecting surface of the light deflecting unit; and a scanning optical system that forms an image on a scanned surface from the light fluxes deflected for the scanning in the deflecting surface of the light deflecting unit, wherein the before-light-deflecting-unit optical system includes: a first optical device which shapes the plurality of light fluxes emitted from the light source; a second optical device made of a resin material which has an anamorphic negative refracting power in a deflection scanning direction and a deflection scan perpendicular direction and has a larger refracting power in the deflection scan perpendicular direction than a refracting power in the deflection scanning direction; and a third optical device made of a glass material which has substantially no refracting power in the deflection scanning direction and a positive refracting power in the deflection scan perpendicular direction, the optical devices being disposed in this order from the light source side, and a focal length of the first optical device, a composite focal length of the second optical device and the third optical device in the deflection scan perpendicular direction, and a lateral magnification ratio of the scanning optical system in the deflection scan perpendicular direction are denoted by fc, fcy, and βs, respectively, and the following Equation (1) is satisfied: 1.5≧|β s×fcy/fc|≧ 1.0 (1).