| 摘要 |
In an optical scanning device, a resin lens having a power that is an inverse (negative) power of a scanning lens is implemented in an optical system placed before a deflector so that a change in beam pitch caused by environmental temperature change can be prevented even when a resin lens is used as the scanning lens. To realize optical scanning using this device, a bundle of rays emitted from a plurality of light sources is coupled into a desired state by a coupling lens, after which the bundle of rays is incident on a resin lens. The surface of incidence of this resin lens has a spherical surface configuration with a negative power, and the exit surface of this resin lens has a cylindrical surface configuration with a negative power only in the sub scanning direction. Then, the bundle of rays passes through a resin lens that has a negative power only in the sub scanning direction and then enters a glass toroidal lens. A light deflector deflects the bundle of rays from the toroidal lens and the deflected bundle of rays is incident on a third optical system that compensates for a field curvature in each of the main scanning direction and the sub scanning direction, and focuses the bundle of rays onto a surface to be scanned while securing a desired beam pitch in the sub scanning direction.
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