Laser scanning unit with meniscus scan lens having asymmetric, negative curvature in the sub-scanning direction and absolute curvature values in the main-scanning direction that are maximal at the center and differing minimal values at each side

摘要

A scanning optical lens used for a laser scanning unit for imaging a laser, which is deflected by a beam deflection unit, on a photosensitive body. The scanning optical lens has a curvature of a Meniscus shape at a sub-scanning direction section, wherein the Meniscus shape has the same curvature symbols at an incidence surface and an exit surface at a center of the lens. The incidence surface and the exit surface always have negative (−) curvature symbols. An absolute curvature value of the incidence surface is maximal at the center, and has at least one minimal value at each of both sides in a main-scanning direction and wherein at least one of the minimal values is approximately zero.