US Patent 7466331 Bow-free telecentric optical system for multiple beam scanning systems

A multiple beam scanning system for scanning light beams onto a photoreceptor of an image forming apparatus. A pre-polygon input and output telecentric optical subsystem includes a beam conditioning system that focuses the light beams in a cross-scan direction, collimates the beams in the scan direction, and individually focuses the beams on a polygonal mirror deflector, which reflects the beams along a first scan path. A post-polygon input and output telecentric optical subsystem redirects the scanned beams along a second scan path and through an output window onto the photoreceptor, wherein the post-polygon subsystem includes a positive cross-scan cylindrical first optical element, a negative cross-scan cylindrical second optical element, and a positive cross-scan cylindrical third optical element. In one embodiment, the three cylindrical optical elements are cylinder mirrors. In another embodiment, one or more of the optical elements are cylinder lenses.