Spatial filtering in interferometry
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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.
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Citations
54 Claims
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1-7. -7. (canceled)
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8. 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 (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 22, 23, 24, 25, 26)
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20. (canceled)
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21. (canceled)
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27. (canceled)
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28. 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 (29, 30, 31, 32, 33, 34, 35, 38, 39, 40, 41, 42, 43, 44, 52, 53)
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36. (canceled)
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37. (canceled)
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45. 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. - View Dependent Claims (46, 47, 48, 49, 50, 51, 54)
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Specification