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US3881823A
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US
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Apparatus for measuring the variation of an optical path length with the aid of an interferometer
Assignee: US Philips Corp
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Filing: 1970-11-12
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Granted: 1975-05-06
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Expires: 1990-11-12
Abstract
Abstract A device for measuring variation of an optical path length with the aid of an interferometer including a laser generating two differently polarized coherent beams which are spatially separated by an isotropic beam splitter and at least one separated beam and preferably both include in their respective paths phase anisotropic elements. A beam splitter recombines the beams and a radiation detector measures the resultant difference. In a further embodiment two detectors are employed and a phase comparison effected. In a still further embodiment, a second isotropic beam splitting unit is employed with a pair of radiation detectors respectively picking up mutually orthogonally polarized beams and generating first and second output signals for comparison.
Inventors
- 👤 Lang Hendrik De
- 👤 Eric Tapley Ferguson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 05:29
CPC Classifications
G; G01; G01B; G01B9/00; G01B9/02; G01B9/02001; G01B9/02007; G01B2290/00; G01B2290/70
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
221 words
A device for measuring the variation of a variable optical path length, comprising optical generating means for producing two orthogonally polarized coherent beams of electromagnetic radiation having different frequencies, a substantially isotropic beam splitting surface for dividing said beams into first and second partial beams each containing both oo said different frequencies, first reflecting means in the path of the first partial beam for redirecting said first partial beam, second reflecting means movable in the direction of the second partial beam and positioned in the path of the second partial beam for redirecting said second partial beam, a phase anisotropic element in the path of at least one of said partial beams for rotating the plane of polarization of the corresponding partial beam by an angle equal to an odd multiple of 90*, a first photodetector, and a polarization-sensitive beam splitter in the path of both redirected partial beams for transmitting at least part of each sub-beam to the first photodetector and for directing a further portion of the radiation from the polarization-sensitive beam splitter to the second photodetector, the portion of the radiation directed to the second photodetector having a plane of polarization substantially orthogonal with respect to the radiation directed to the first photodetector, the radiation directed to each photodetector containing both frequencies produced by the optical generating means.
Claim 2
Independent Claim
221 words
A device for measuring the variation of a variable optical path length, comprising optical generating means for producing two orthogonally polarized coherent beams of electromagnetic radiation having different frequencies, a substantially isotropic beam splitting surface for dividing said beams into first and second partial beams each containing both oo said different frequencies, first reflecting means in the path of the first partial beam for redirecting said first partial beam, second reflecting means movable in the direction of the second partial beam and positioned in the path of the second partial beam for redirecting said second partial beam, a phase anisotropic element in the path of at least one of said partial beams for rotating the plane of polarization of the corresponding partial beam by an angle equal to an odd multiple of 90*, a first photodetector, and a polarization-sensitive beam splitter in the path of both redirected partial beams for transmitting at least part of each sub-beam to the first photodetector and for directing a further portion of the radiation from the polarization-sensitive beam splitter to the second photodetector, the portion of the radiation directed to the second photodetector having a plane of polarization substantially orthogonal with respect to the radiation directed to the first photodetector, the radiation directed to each photodetector containing both frequencies produced by the optical generating means.
Claim 3
Independent Claim
269 words
A device for measuring the variation of a variable optical path length, comprising optical generating means for producing two orthogonally polarized beams of electromagnetic radiation each having a different frequency, an isotropic beam splitter in the path of the radiation from the optical generating means for dividing the radiation from the optical generating means into a first and a second partial beam each containing both frequencies of coherent radiation, a first reflecting means in the path of the first partial beam for redirecting the first partial beam toward the isotropic beam splitter, a second reflecting means mounted for movement along the path of the second partial beam for redirecting the second partial beam toward the isotropic beam splitter, a phase anisotropic element in the path of at least one of the partial beams for rotating the plane of polarization of the corresponding partial beam by an angle equal to an integral multiple of 90*, a polarizatIon-sensitive beam splitter in the path of the redirected partial beams emanating from the isotropic beam splitter, the polarization-sensitive beam splitter being positioned to reflect substantially all the radiation of a first polarization and to pass substantially all the radiation of an orthogonal polarization thereby to separate the redirected partial beams into a third and fourth partial beam each containing coherent radiation of a single polarization direction and each containing both frequencies produced by the optical generating means, a first photo-detector in the path of the third partial beam, a second photo-detecctor in the path of the fourth partial beam, and electronic means for comparing the electrical output of the first and second photo-detectors.
Claim 4
Independent Claim
269 words
A device for measuring the variation of a variable optical path length, comprising optical generating means for producing two orthogonally polarized beams of electromagnetic radiation each having a different frequency, an isotropic beam splitter in the path of the radiation from the optical generating means for dividing the radiation from the optical generating means into a first and a second partial beam each containing both frequencies of coherent radiation, a first reflecting means in the path of the first partial beam for redirecting the first partial beam toward the isotropic beam splitter, a second reflecting means mounted for movement along the path of the second partial beam for redirecting the second partial beam toward the isotropic beam splitter, a phase anisotropic element in the path of at least one of the partial beams for rotating the plane of polarization of the corresponding partial beam by an angle equal to an integral multiple of 90*, a polarizatIon-sensitive beam splitter in the path of the redirected partial beams emanating from the isotropic beam splitter, the polarization-sensitive beam splitter being positioned to reflect substantially all the radiation of a first polarization and to pass substantially all the radiation of an orthogonal polarization thereby to separate the redirected partial beams into a third and fourth partial beam each containing coherent radiation of a single polarization direction and each containing both frequencies produced by the optical generating means, a first photo-detector in the path of the third partial beam, a second photo-detecctor in the path of the fourth partial beam, and electronic means for comparing the electrical output of the first and second photo-detectors.
Claim 5
Dependent Claim
35 words
A combination of claim 1, wherein the first and second reflecting means comprise means for redirecting the impinging first and second partial beams along a path parallel to and displaced from the respective impinging beams.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-05-05 | 1978-11-04 | 1979-05-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-05-05 | 1982-11-04 | 1983-05-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-05-05 | 1986-11-04 | 1987-05-06 | $7700.00 | Window Closed / Lapsed |