LASER SCANNING UNIT

摘要

A laser scanning unit is provided to improve injection molding of a lens by making the edge of the lens become relatively thick in the range of the central thickness of the lens and correct a curvature of image field of a main scanning direction within an error range to improve picture quality of an image forming apparatus. A laser scanning unit includes a light source(110), a collimating unit(112), a rotatory polygon mirror(120), and a lens(130). The collimating unit collimates light emitted from the light source. The rotatory polygon mirror deflects light projected from the collimating unit. The lens forms an image corresponding to the light deflected by the rotatory polygon mirror on a to-be-scanned plane at an equal speed and corrects a curvature of image field of a main scanning direction. The lens has a convex meniscus shape. The curvature of the main scanning direction and the curvature of the sub-scanning direction of the lens are different from each other. The lens has an aspherical shape in which the curvature of the sub-scanning direction is continuously changed. The ratio of the radius of curvature of a first plane of the lens to the radius of curvature of a second plane on an optical axis is greater than 1.7.