Fast scan spot correction in a polygon ros using pwm

A raster scanning system includes a beam generator (6) which generates a beam of radiant energy in response to a drive signal. The drive signal comprising a series of pulses. The raster scanning system includes a polygon (4) having an overfilled facet design in which a plurality of facets are at least partially positioned in the optical path of the beam of radiant energy regardless of the rotational position of the polygon. The polygon is adapted to scan a spot across a beam receiving surface. The raster scanning system includes spot size correcting means for maintaining a constant spot size of the scanned spot from start of scan (WSOS) to end of scan (WEOS) by modulating the pulse width of the drive signal provided to the beam generator.