Characterization and compensation of non-cyclic errors in interferometry systems
First Claim
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1. A method comprising:
- providing a test interferometer which during operation directs two beams along different paths and then combines them to produce an output beam, wherein the output beam comprises information about an optical path length difference between the two beams, wherein imperfections in the test interferometer cause a measurable interferometric test phase derived from the output beam to deviate 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, wherein the deviation comprises a non-cyclic error term that varies in a nonperiodic way on the optical path length difference;
using the test interferometer to measure the test phase as a function of a test parameter that causes the optical path length difference to vary;
comparing the measured test phase to another expression indicative of the optical path length difference; and
determining a representation indicative of the non-cyclic error term for the test interferometer based on the comparison.
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Abstract
Systems and methods for characterizing and compensating non-cyclic errors in interferometers and interferometer components are disclosed.
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Citations
66 Claims
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1. A method comprising:
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providing a test interferometer which during operation directs two beams along different paths and then combines them to produce an output beam, wherein the output beam comprises information about an optical path length difference between the two beams, wherein imperfections in the test interferometer cause a measurable interferometric test phase derived from the output beam to deviate 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, wherein the deviation comprises a non-cyclic error term that varies in a nonperiodic way on the optical path length difference;
using the test interferometer to measure the test phase as a function of a test parameter that causes the optical path length difference to vary;
comparing the measured test phase to another expression indicative of the optical path length difference; and
determining a representation indicative of the non-cyclic error term for the test interferometer based on the comparison. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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38. An apparatus comprising:
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a test interferometer which during operation directs two beams along different paths and then combines them to produce an output beam, wherein the output beam comprises information about an optical path length difference between the two beams, wherein imperfections in the interferometer causes a measurable interferometric phase derived from the output beam to deviate 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, wherein the deviation comprises a non-cyclic error term that varies in a nonperiodic way on the optical path length difference; and
an electronic storage medium providing a representation indicative of the non-cyclic error term for the test interferometer. - View Dependent Claims (39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 60, 61)
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53. An interferometry method comprising:
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positioning a test interferometer relative to a measurement object, wherein during operation of the test interferometer directs two beams along different paths and then combines them to produce an output beam, wherein at least one of the beams contacts the measurement object and the output beam comprises information about an optical path length difference between the two beams, wherein imperfections in the interferometer causes a measurable interferometric phase derived from the output beam to deviate 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, wherein the deviation comprises a non-cyclic error term that varies in a nonperiodic way on the optical path length difference;
correcting the measured phase based on a representation indicative of the non-cyclic error term for the test interferometer; and
monitoring the position of the measurement object based on the corrected phase. - View Dependent Claims (54, 55, 56, 57, 58, 59, 62, 63, 64, 65, 66)
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Specification