Scanner and image forming apparatus including a pre-deflection lens that has a width reduced by an emission-side concavity and that converges light incident on areas other than the thinned portion

摘要

A cylindrical lens is positioned between and a polygon mirror and a second slit plate through which light beams from two light beam emitting units pass, and the cylindrical lens has a thin portion where the thickness between the entrance plane and the emission plane is reduced by forming the cylindrical lens in a shape created by cutting off a surface top part of the entrance plane having a convex cross section. The light beams passed through the second slit plate pass through light converging portions provided on both sides of the thin portion of the cylindrical lens in a sub-scanning direction, and are converged on a focal point on a deflecting plane of the polygon mirror.