Patent ID: 7274498
Filing Date: 2007-09-25
Classification: G02B

Abstract:
1. An optical scanning device for scanning a surface along a line comprising: a radiation source unit for supplying at least one primary radiation beam, an optical system for focusing the at least one primary radiation beam to a spot on the surface to be scanned, and a rotatable polygon mirror comprising a number of mirror facets for deflecting the at least one primary radiation beam through a variable deflection angle, thereby obtaining a scanning beam, and to direct the scanning beam to a position on the surface to be scanned, said optical system comprising: a main imaging system which is arranged in a first radiation path of the scanning beam between the radiation source unit and the rotatable polygon mirror; a correction system which is arranged in a second radiation path of the scanning beam between the rotatable polygon mirror and the surface to be scanned, and facet tracking means for deflecting the at least one primary radiation beam in synchronism with rotation of the rotatable polygon mirror such that a ray of the primary beam is continuously directed at substantially a center of a facet of the mirror facets that is momentarily illuminated by the at least one primary radiation beam, wherein the tracking means are operable to create a deflection point for the scanning beam, said deflection point being located between a center of rotation of the rotatable polygon mirror and the facet upon which the at least one primary radiation beam is momentarily incident.