Optical scanning device

Abstract

An optical scanning device having: a beam diameter shaping optical system which shapes a diameter of a light beam from a light source and focuses the light beam as a line image which is long in a direction corresponding to a main scanning direction; polygon mirror having a reflecting surface at one of a focusing position and a vicinity of the focusing position of the line image, the polygon mirror deflecting a light beam, which is incident on the polygon mirror, at a uniform angular speed in the direction corresponding to the main scanning direction; a cylindrical mirror disposed at a light beam reflecting side of the polygon mirror, the cylindrical mirror having power to converge a light beam in only a subscanning direction which is orthogonal to the main scanning direction, and converging a light beam on a surface-to-be-scanned; and an f .theta. lens system disposed between the polygon mirror and the cylindrical mirror, and having power to converge a light beam only in a main scanning direction, and converging a light beam, which is incident on the f .theta. lens system, onto the surface-to-be-scanned via the cylindrical mirror so that a light spot is scanned at a uniform speed. Because the f .theta. lens system only has power in the main scanning direction, a configuration of each lens of the f .theta. lens system can be made simple and compact.

Dependencies are inferred from the claim text.