Abstract

A raster scanning system is disclosed which utilizes a focus error correction system and a pre-polygon cross-scan cylindrical lens for correcting focus error both in the fast-scan plane and in the cross-scan plane without affecting the scan characteristics of the post polygon optics. The focus error correction system comprises at least two lenses which can be either spherical or fast-scan cylindrical lenses and one of the lenses must be axially adjustable. By adjusting the adjustable lens, a positive or a negative optical power can be added to a beam passing through the focus error correction system in order to correct the focus error in the fast-scan plane. The pre-polygon cross-scan cylindrical lens is also adjustable to correct the focus error in the cross-scan plane.