Patent ID: 7554708

Claim:
An optical scanning device comprising: a first optical element that converts a cross-section shape of a light beam from a semiconductor laser to a desired shape; a second optical element that guides the light beam output from the first optical element to an optical deflector that deflects the light beam; and a third optical element that gathers the light beam deflected by the optical deflector onto a surface to be scanned to form a light spot thereby optically scanning the surface, wherein at least one of lenses forming the first optical element and the second optical element includes a resin-made lens, at least one of resin-made lenses satisfies conditions (1) to (4): (1) only one surface of the resin-made lens has a diffracting surface |P3|≧|P1+P2| (2) |P1|>|P1+P2|and |P2|≧|P1+P2| (3) P1ΔP3>0 (4 ) where P1 is a power in any of a main scanning direction and a sub-scanning direction of a diffracting portion on a diffracting surface of the resin-made lens, P2 is a power of a refractive portion on the diffracting surface in the direction defined in P1, and P3 is a power on a surface other than the diffracting surface of the resin-made lens in the direction defined in P1.