Flattening the field of postobjective scanners by optimum choice and positioning of polygons

Polygonal mirrors are commonly used in laser beam scanning. The paper gives some useful geometrical formulas for their basic dimensions when used as parallel as well as convergent beam scanners. The first part deals with underfilled polygons that are used in parallel beam scanning. In the second part, a method is outlined for obtaining a nearly flat field in convergent beam scanning. This method enables the use of relatively fast but simple spot-forming lenses in postobjective scan systems resulting in scan resolutions that are sometimes comparable to the resolutions given by preobjective scanners with complex F-theta lenses.