| 摘要 |
The present invention provides an optical scanning apparatus capable of satisfactorily correcting a field curvature caused by spherical aberration in an incidence optical system, and an image forming apparatus using the same. A light beam emitted from light source means is guided to an optical deflector for deflecting the light beam through a first optical system having a collimating operation, and a second optical system including a surface having a beam expanding operation and an aspherical operation for compensating for aberration in order. When the light beam deflected by the optical deflector is guided to a surface to be scanned through a third optical system, the light beam emitted from the light source means is converted into a nearly collimated light beam through the first and second optical systems within a main scanning cross section and is made incident on a deflecting surface of the optical deflector to make its width wider than that of the deflecting surface thereof in a main scanning direction. Thus, a surface of the second optical system having an aspherical operation compensates for a spherical aberration generated in the first optical system.
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