Polygon scanner having a fluid film bearing and active correction of

Abstract

A polygon scanner utilizing a fluid film bearing and method for its use in a flat field imaging device having a relatively large format size, a very high scan rate and high resolution. The polygon scanner has a polygon scan optic connected to a motor, a fluid film bearing, and a windowed enclosure. Repeating cross-scan error components are mapped and actively corrected using a piezoelectric actuator to directly displace the laser element or using a mirror in the optical path that is tilted by means of an electro-optic device to influence a virtual displacement of the optical beam. The repeating components of in-scan errors are similarly, and independently, mapped and corrected by summing with the output of a phase detector in a line scan speed control system. Methods for independently correcting the errors associated with cross-scan and in-scan components in the scan optic are significantly enhanced by the use of a fluid film bearing in general and a self-acting gas bearing in particular, supporting the rotating polygon scan optic. A method for periodic calibration of the cross-scan error map established at the factory may be implemented by a self-calibration sub-routine using a stored sinusoidal voltage waveform. This simplified calibration technique of the invention is enabled by the use of a fluid film bearing in general and a self-acting gas bearing in particular.