Optical printing systems often use a scanning process. Many of such systems use a laser which produces a circularly symmetrical gaussian beam and a rotating polygon mirror which line scans the laser beam across a photosensitive member at an image zone. The mirrored facets of the polygon when assembled have "tilt errors" commonly referred to as pyramidal errors. These errors may cause unacceptable artifacts in the recorded image. To correct for tilt error, some printers use a cylindrical lens or mirror to optically conjugate the polygon and the image plane in the direction perpendicular to the scan direction. The beam is shaped anamorphically prior to its arrival at the polygon. Examples for such systems are the systems described in U.S. Pat. Nos. 4,040,096 to Starkweather, 4,247,160 to Brueggemann and 4,318,583 to Goshima et al.
Anamorphic shaping of laser beams is also done in optical systems using semiconductor laser diodes. Laser diodes typically produce an initially anamorphic gaussian beam. It is desirable to anamorphically shape that anamorphic beam into a circularly symmetrical gaussian beam. U.S. Pat. No. 3,974,507 sets forth a method for shaping an anamorphic gaussian beam produced by the diode laser into a circularly symmetrical beam using cylindrical lenses. Other examples using cylindrical lenses are set forth in U.S. Pat. Nos. 4,318,594 and 4,253,735. A disadvantage of cylindrical elements such as lenses and mirrors to anamorphically shape gaussian laser beams is that they are difficult to manufacture.