Patent ID: 7636166
Filing Date: 2009-12-22
Classification: G01B,G03F

Abstract:
1. A system, comprising: a first object mounted relative to a second object, the first object being moveable with respect to the second object; a plurality of interferometers each configured to derive a first wavefront and a second wavefront from input radiation and to combine the first and second wavefronts to provide output radiation comprising information about an optical path length difference between the paths of the first and second wavefronts, each interferometer comprising a reflective element positioned in the path of the first wavefront and mounted on the first object, where the reflective element for each interferometer is mounted at a different location on the first object relative to the reflective elements for the other interferometers; a plurality of fiber waveguides, each fiber waveguide being configured to deliver the input radiation to a corresponding interferometer and direct the output radiation from the corresponding interferometer to a corresponding detector; and an electronic controller coupled to the corresponding detectors and programmed to monitor, for each interferometer, a corresponding degree of freedom of the first object relative to the second object based on the information from at least one of the interferometers, wherein the degree of freedom for each interferometer is an absolute displacement between the first and second objects.