Apparatus and method(s) for reducing the effects of coherent artifacts in an interferometer
First Claim
1. Apparatus for illuminating an object under test in an interferometer having an optical axis, said apparatus comprising:
- at least one source of radiation; and
means for directing radiation from said source at the object from different locations that are distant from the optical axis such that radiation from said locations is incident to the same points on the object along optical paths having substantially identical optical path differences within the interferometer.
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Accused Products
Abstract
Interferometric apparatus and methods for reducing the effects of coherent artifacts in interferometers. Fringe contrast in interferograms is preserved while coherent artifacts that would otherwise be present in the interferogram because of coherent superposition of unwanted radiation generated in the interferometer are suppressed. Use is made of illumination and interferogrammetric imaging architectures that generate individual interferograms of the selected characteristics of a test surface from the perspective of different off-axis locations of illumination in an interferometer and then combine them to preserve fringe contrast while at the same time arranging for artifacts to exist at different field locations so that their contribution in the combined interferogram is diluted.
14 Citations
88 Claims
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1. Apparatus for illuminating an object under test in an interferometer having an optical axis, said apparatus comprising:
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at least one source of radiation; and
means for directing radiation from said source at the object from different locations that are distant from the optical axis such that radiation from said locations is incident to the same points on the object along optical paths having substantially identical optical path differences within the interferometer. - 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)
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25. An interferometric apparatus having an optical axis, said interferometric apparatus comprising:
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means for locating an object to be measured along the optical axis;
an optical arrangement adapted to at least in part cooperate with an object to form an interferometer and facilitate the generation of interfering wavefronts in which phase information about the object is encoded; and
means for directing radiation onto the object to be measured from different locations that are distant from said optical axis such that radiation from said locations is incident to the same points on the object along optical paths having substantially identical optical path differences within said interferometer to generate interfering wavefronts corresponding to each of said locations where each wavefront contains substantially identical phase information about the object from said interferometer. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52)
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53. An illumination method for use with an interferometer having an optical axis, said illumination method comprising the steps of:
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generating radiation from at least one source; and
directing radiation from said at least one source toward an object to be measured from different locations that are distant from said optical axis such that radiation from said locations is incident to the same points on the object along optical paths having substantially identical optical path differences within the interferometer. - View Dependent Claims (54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69)
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70. An interferometric method comprising the steps of:
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locating an object to be measured along an optical axis;
arranging optical components adapted to at least in part cooperate with an object to form an interferometer and facilitate the generation of interfering wavefronts in which phase information about the object is encoded; and
directing radiation onto the object to be measured from different locations that are distant from said optical axis such that radiation from said locations is incident to the same points on the object along optical paths having substantially identical optical path differences within said interferometer to generate interfering wavefronts corresponding to each of said locations where each wavefront contains substantially identical phase information about the object from said interferometer. - View Dependent Claims (71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84)
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85. Apparatus for illuminating an object under test in an interferometer having an optical axis, said apparatus comprising:
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at least one source of radiation; and
means for directing radiation from said source at the object from different locations that are distant from the optical axis such that radiation from said locations is incident to the same points on the object along optical paths having substantially identical optical path differences within the interferometer, wherein said different locations comprise at least two that are equidistant from the optical axis, oppositely spaced along an azimuth through said optical axis, and wherein radiation therefrom is mutually coherent.
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86. An interferometric apparatus having an optical axis, said interferometric apparatus comprising:
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means for locating an object to be measured along the optical axis;
an optical arrangement adapted to at least in part cooperate with an object to form an interferometer and facilitate the generation of interfering wavefronts in which phase information about the object is encoded; and
means for directing radiation onto the object to be measured from different locations that are distant from said optical axis such that radiation from said locations is incident to the same points on the object along optical paths having substantially identical optical path differences within said interferometer to generate interfering wavefronts corresponding to each of said locations where each wavefront contains substantially identical phase information about the object from said interferometer, wherein said different locations comprise at least two that are equidistant from the optical axis, oppositely spaced along an azimuth through said optical axis, and wherein radiation therefrom is mutually coherent.
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87. An Illumination method for use with an interferometer having an optical axis, said illumination method comprising the steps of:
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generating radiation from at least one source; and
directing radiation from said at least one source toward an object to be measured from different locations that are distant from said optical axis such that radiation from said locations is incident to the same points on the object along optical paths having substantially identical optical path differences within the interferometer, wherein said different locations comprise at least two that are equidistant from the optical axis, oppositely spaced along an azimuth through said optical axis, and wherein radiation therefrom is mutually coherent.
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88. An interferometric method comprising the steps of:
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locating an object to be measured along an optical axis;
arranging optical components adapted to at least in part cooperate with an object to form an interferometer and facilitate the generation of interfering wavefronts in which phase information about the object is encoded; and
directing radiation onto the object to be measured from different locations that are distant from said optical axis such that radiation from said locations is incident to the same points on the object along optical paths having substantially identical optical path differences within said interferometer to generate interfering wavefronts corresponding to each of said locations where each wavefront contains substantially identical phase information about the object from said interferometer, wherein said different locations comprise at least two that are equidistant from the optical axis, oppositely spaced along an azimuth through said optical axis, and wherein radiation therefrom is mutually coherent.
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Specification