Patent ID: 6788446
Filing Date: 2004-09-07
Classification: G02B

Abstract:
An optical scanning apparatus for optically scanning a surface to be scanned at a constant velocity, the optical scanning apparatus comprising:a light source for emitting a light flux; a first optical lens system for coupling the light flux emitted by the light source to a following optical lens system; a second optical lens system for forming the light flux from the first optical lens system into a line image extending in a direction corresponding to a main scanning direction of the surface to be scanned which is perpendicular to a sub scanning direction; an optical deflector for deflecting the light flux formed as the line image via a deflecting reflective plane thereof which is located near where the line image is formed; and a third optical lens system for condensing the deflected light flux as an optical beam spot on the surface to be scanned; wherein the second optical lens system includes a glass lens and at least one plastic lens having a non-arc shape, wherein the at least one plastic lens has a negative power in the sub scanning direction, said non-arc shape being formed in the subscanning direction, and a variation in a curvature of an imaging point of the second optical lens system is opposite to that in a curvature of an imaging point of the third optical lens system in the sub-scanning direction in accordance with a change in temperature.