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 changes in the orientation of the measurement object cause a displacement of the first beam from a nominal beam path, and wherein the first and second beams are derived from a common source;
spatial filtering the first beam after it contacts the measurement object, wherein the spatial filtering reduces the displacement of the first beam from the optical path; 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, wherein the first beam is spatially filtered prior to being combined with the second beam.
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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
73 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 changes in the orientation of the measurement object cause a displacement of the first beam from a nominal beam path, and wherein the first and second beams are derived from a common source;
spatial filtering the first beam after it contacts the measurement object, wherein the spatial filtering reduces the displacement of the first beam from the optical path; 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, wherein the first beam is spatially filtered prior to being combined with the second beam. - View Dependent Claims (2, 3, 4, 5)
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6-54. -54. (Canceled)
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55. A method, comprising:
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directing a first beam and a second beam along respective paths using a high stability plane mirror interferometer, wherein the first beam contacts a measurement object and wherein the first and second beams are derived from a common source;
spatial filtering the first beam 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 (56, 57, 58, 59, 60)
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61. 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 more than once and wherein the first and second beams are derived from a common source;
spatial filtering the first beam 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 (62, 63, 64, 65)
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66. 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;
spatial filtering the first beam 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, wherein the first beam is spatially filtered prior to being combined with the second beam. - View Dependent Claims (67, 68, 69)
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70. 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 more than once 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
a spatial filter positioned in the path of the first beam, wherein the spatial filtering reduces the displacement of the first beam from the nominal beam path. - View Dependent Claims (71, 72)
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73. An apparatus, comprising:
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a high stability plane mirror 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
a spatial filter positioned in the path of the first beam, wherein the spatial filtering reduces the displacement of the first beam from the nominal beam path.
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Specification