Patent ID: 7474409
Filing Date: 2009-01-06
Classification: G01B,G03F

Abstract:
1. An interferometer system for measuring displacement of an object in a plane substantially parallel to a two dimensional plane, said interferometer system comprising: a plane mirror interferometer system; a differential plane mirror interferometer system; a beam-splitter configured to split a radiation beam associated with said plane mirror interferometer system and a radiation beam associated with said differential plane mirror interferometer system into respective measuring beams and respective reference beams, and a first reflector coupled to the beam-splitter, the first reflector configured to change a direction of propagation of the reference beam associated with the differential plane mirror interferometer system such that the reference beam associated with the differential plane mirror interferometer system exits the first reflector away from the beam-splitter in a substantially orthogonal direction to the reference beam associated with the plane mirror interferometer that exits the beam-splitter.