Patent ID: 7362486

Claim:
An optical scanning device comprising: a light source that emits a light beam; a first optical system that guides the light beam emitted by the light source; an optical deflector that deflects the light beam guided by the first optical system; and a second optical system that converges the light beam deflected by the optical deflector on a surface to be scanned, wherein the first optical system includes at least one resin lens having a diffractive surface, the second optical system includes at least one resin optical element, and a beam diameter depth in a main scanning direction, Wm, that can have a maximum intensity of 1/e 2 , satisfies conditions Δ m 1 Δm 2 Δm 3 −Δd 1×( f 2 /f 1) 2 <Wm/ 40 (1) Δd1>0 and Δm2<0 (2) where, Δm 1 is a beam waist position shift in the main scanning direction due to a change in the power in a refracting unit when the temperature in the first optical system rises by 1° C., Δm 2 is a beam waist position shift in the main scanning direction due to a change in the power in a diffracting unit when the temperature in the first optical system rises by 1° C., Δm 3 is a beam waist position shift in the main scanning direction when the temperature in the second optical system rises by 1° C., Δd 1 is a shift in the distance between a forward principal point of the first optical system in the main scanning direction and the light source when the temperature in the first optical system rises by 1° C., f 1 is a focal distance of the first optical system in the main scanning direction, and f 2 is a focal distance of the second optical system in the main scanning direction.