Optical scanning apparatus

摘要

An optical scanning apparatus is capable of successfully compensating for field curvature and/or distortion aberration and of minimizing the influences of a change in spot diameter in the sub-scanning direction attributable to a change in the height of an image. The optical scanning apparatus is equipped with: a first optical device for converting a luminous flux emitted from light source means into a convergent light beam; a second optical device for forming the luminous flux into a line-shaped, longitudinal image in a main scanning direction on a deflecting facet of a deflecting device; and a third optical device for forming the luminous flux which has been deflected by the deflecting device into a spot-shaped image on a plane to be scanned; wherein the third optical device has a first toric lens and a second toric lens disposed in the mentioned order from the deflecting device, the first toric lens has both surfaces thereof formed into aspherical shapes in the main scanning cross section and it has a meniscus shape which provides a concave surface facing the deflecting device in the vicinity of the center of scanning and which provides a positive refractive power; the second toric lens has both surfaces thereof formed into aspherical shapes in the main scanning cross section and it has a meniscus shape which provides a convex surface facing the deflecting device in the vicinity of the center of scanning and which provides a positive refractive power; and the sections of the first toric lens and the second toric lens perpendicular to a generating line in a sub-scanning cross section both have meniscus shapes which provide concave surfaces facing the deflecting device and which provide a positive refractive power. <IMAGE>