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US 2003/0211402 A1Published application
Spatial filtering in interferometry
AssigneeZygo Corporation
InventorHenry A. Hill
Life of this patent
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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.
Claims54
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.
1 more element
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;
- 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.
1 more element
A method, comprising:
- directing a first beam and a second beam along respective paths, wherein the first and second beams are derived from a common source;
- 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;
- and
- spatial filtering the first beam, wherein the spatial filtering reduces deviations of a measurable interferometric phase derived from the output beam from the expression Φ=pknL, where p is an integer, k is the wavenumber of the output beam, and nL corresponds to the optical path length difference.
1 more element
An apparatus, comprising:
- 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
- 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.
A method for monitoring the position of a measurement object, comprising:
- 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;
- spatial filtering the first beam 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.
3 more elements
Dependencies are inferred from the claim text.