Error compensation in phase shifting interferometry
First Claim
1. A method, comprising:
- combining reference light reflected from a reference surface with test light reflected from a test surface to form combined light, the test and reference light being derived from a common source;
sinusoidally varying a phase between the test light and reference light, where the sinusoidal phase variation has an amplitude u;
recording at least one interference signal related to changes in an intensity of the combined light in response to the sinusoidal variation of the phase;
determining information related to the phase using a phase shifting algorithm that has a sensitivity that varies as a function of the sinusoidal phase shift amplitude, where the sensitivity of the algorithm at 2 u is 10% or less of the sensitivity of the algorithm at u.
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Abstract
In certain aspects, disclosed methods include combining reference light reflected from a reference surface with test light reflected from a test surface to form combined light, the test and reference light being derived from a common source, sinusoidally varying a phase between the test light and reference light, where the sinusoidal phase variation has an amplitude u, recording at least one interference signal related to changes in an intensity of the combined light in response to the sinusoidal variation of the phase, determining information related to the phase using a phase shifting algorithm that has a sensitivity that varies as a function of the sinusoidal phase shift amplitude, where the sensitivity of the algorithm at 2 u is 10% or less of the sensitivity of the algorithm at u.
35 Citations
37 Claims
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1. A method, comprising:
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combining reference light reflected from a reference surface with test light reflected from a test surface to form combined light, the test and reference light being derived from a common source; sinusoidally varying a phase between the test light and reference light, where the sinusoidal phase variation has an amplitude u; recording at least one interference signal related to changes in an intensity of the combined light in response to the sinusoidal variation of the phase; determining information related to the phase using a phase shifting algorithm that has a sensitivity that varies as a function of the sinusoidal phase shift amplitude, where the sensitivity of the algorithm at 2 u is 10% or less of the sensitivity of the algorithm at u. - 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)
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32. A method, comprising:
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combining reference light reflected from a reference surface with test light reflected from a test surface to form combined light, the test and reference light being derived from a common source; sinusoidally varying a phase between the test light and reference light; recording at least one interference signal based on a modulation of the combined light in response to varying the phase; determining information related to the phase using a phase shifting algorithm that has a sensitivity to contributions to the combined light from test light that makes a double pass between the test and reference surfaces that is 10% or less of the sensitivity of the algorithm to contributions to the combined light from test light that makes a single pass between the test and reference surfaces.
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33. A system, comprising:
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an interferometer which during operation combines test light from a test surface with reference light from a reference surface to form combined light, where the test and reference light are derived from a common source; a phase shifting component which during operation introduces a sinusoidal phase shift between the test light and reference light, where the sinusoidal phase variation has an amplitude u; a detector positioned to detect the combined light and provide at least one interference signal based on the modulation of the combined light beam in response to varying the phase; and an electronic controller coupled to the phase shifting component and the detector, wherein the electronic controller is configured to determine information related to the phase during operation of the system, where the electronic controller determined the information using a phase shifting algorithm that has a sensitivity that varies as a function of the sinusoidal phase shift amplitude, where the sensitivity of the algorithm at 2 u is 10% or less of the sensitivity of the algorithm at u. - View Dependent Claims (34, 35, 36)
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37. A method, comprising:
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combining reference light reflected from a reference surface with test light reflected from a test surface to form combined light, the test and reference light being derived from a common source; sinusoidally varying a phase between the test light and reference light, where the sinusoidal phase variation has an amplitude u; recording at least one interference signal related to changes in an intensity of the combined light in response to the sinusoidal variation of the phase; determining information related to the phase using a phase shifting algorithm that has a sensitivity that varies as a function of the sinusoidal phase shift amplitude, wherein the sensitivity of the algorithm has a minimum close to 2 u and in a range from 2 u+−
0.2 u, the sensitivity is 10% or less of the sensitivity of the algorithm at u to suppress calibration errors in u.
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Specification