Patent ID: 7570278

Claim:
An optical scanning device comprising: a light source including a semiconductor laser that generates a light beam; a coupling optical system that couples the light beam from the light source and changes the light beam to a diverging light beam, wherein the coupling optical system includes at least one lens; a first optical system that changes the diverging light beam from the coupling optical system to a parallel beam in a main scanning direction and to a focused light beam, which is focused on a deflector, in a sub-scanning direction; the deflector that deflects the light beam from the first optical system to the main scanning direction; and a scanning optical system that condenses the light beam deflected by the deflector, wherein the at least one lens in the coupling optical system is made of resin, and the at least one lens in the coupling optical system has a diffractive optical surface at least on one surface thereof, and the diffractive optical surface has a plurality of protruding rings having tips disposed on a spherical, concave surface facing the light source, and a phase function φ(h) of the diffractive optical surface is given by φ( h ) =C 1 ·h 2 +C 2 ·h 4 +C 3 ·h 6 +C 4 ·h 8 +C 5 ·h 10 , where φ(h) is an even power series, C 1 to C 5 are constants, and h is a distance from an optical axis.