US Patent 7508564 Scanning optical apparatus

A scanning optical apparatus capable of keeping sub scanning magnification small, arid further, of keeping the apparatus size small without elongating lenses, also suppresses spherical aberration relative to a scanning surface of a beam light small, thereby illuminating the beam light of high quality on the scanning surface. A beam light from a scanner is magnified by a scanning lens (magnifying lens). This allows sub scanning magnification to be minimized. Also, spherical aberration which is ordinarily aggravated since the beam light is magnified by the scanning lens is suppressed by arranging a correcting lens in the downstream from the scanning lens, as being decentered relative to a light axis of the beam light.