Spatial filtering in interferometry
First Claim
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1. A method, comprising:
- directing a first beam and a second beam along respective paths, wherein the first beam contacts a measurement object and wherein the first and second beams are derived from a common source;
passing the first beam through an aperture after it contacts the measurement object; and
combining the first and second beams to form an output beam, wherein the output beam comprises information about an optical path length difference between the first and second beams.
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Abstract
Spatial filtering of beams in interferometry systems is used to reduce a displacement of the beams from an optical path corresponding to the path of the beams in an optimally-aligned system. By reducing beam displacement from the optical path, the system reduces the magnitude of beam shears and associated non-cyclic errors in linear and angular displacements measured by the interferometry systems.
46 Citations
30 Claims
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1. A method, comprising:
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directing a first beam and a second beam along respective paths, wherein the first beam contacts a measurement object and wherein the first and second beams are derived from a common source; passing the first beam through an aperture after it contacts the measurement object; and combining the first and second beams to form an output beam, wherein the output beam comprises information about an optical path length difference between the first and second beams. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. An apparatus, comprising:
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an interferometer which during operation directs a first beam and a second beam along respective paths and then combines the first and second beams to produce an output beam, wherein the first beam contacts a measurement object and changes in the orientation of the measurement object cause a displacement of the first beam from a nominal beam path, and wherein the output beam comprises information about an optical path length difference between the first and second beams; and an aperture positioned in the path of the first beam to reduce the displacement of the first beam from the nominal beam path. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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30. A method for monitoring the position of a measurement object, comprising:
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directing a first beam and a second beam along respective paths, wherein the first beam contacts the measurement object and wherein the first and second beams are derived from a common source; passing the first beam through an aperture after it contacts the measurement object; combining the first and second beams to form an output beam; detecting a phase of the output beam related to an optical path length difference between the first and second beams; and monitoring the position of the measurement object based on the detected phase.
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Specification