Patent ID: 7050210

Claim:
A multi-beam optical scanning device, comprising: a light source having a plurality of emission points that emit a bundle of rays; a first optical system that couples the bundle of rays emitted from the light source; a second optical system that condenses the bundle of rays from the first optical system into a substantially linear state extending along a main scanning direction; a light deflector that has a deflection surface arranged close to where the bundle of rays is condensed, wherein the bundle of rays is deflected by said deflection surface; a third optical system that condenses the deflected bundle of rays onto a surface to be scanned as a plurality of light spots; wherein the third optical system has at least one resin imaging element; the second optical system has at least one resin imaging element and at least one glass imaging element; and a power of each surface of the resin imaging element of the second optical system is arranged so that a change in a beam pitch in a sub scanning direction caused by a temperature change in at least one of the first optical system and the third optical system satisfies a condition: Δ P ′<0.5 /DPI (mm/° C.) wherein ΔP′ denotes a measure of change in the sub scanning beam pitch on an image surface for every 1° C. temperature change (mm/° C.), and DPI denotes a write density (dots/inch).