Patent ID: 6271923
Filing Date: 2001-08-07
Classification: G01B,G03F

Abstract:
An interferometry system comprising:an interferometer which during operation directs a measurement beam along a measurement path contacting a measurement object and combines each of at least two portions of the measurement beam with a corresponding reference beam to form at least two overlapping pairs of exit beams, the interferometer comprising a beam steering assembly having a beam steering element and a positioning system to orient the beam steering element, the beam steering element positioned to direct the measurement beam to the measurement object, the measurement beam contacting the beam steering element;a control circuit which during operation causes the positioning system to reorient the beam steering element in response to a change in angular orientation of the measurement object; andan angle measurement system which during operation calculates the change in angular orientation of the measurement object based on at least one of interferometric signals derived from the overlapping pairs of exit beams and the reorientation of the beam steering element.