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US 4,360,271 AGranted
Interferometer systems
AssigneeNational Research Development Corporation
InventorsMichael J. Downs, Kenneth W. Raine
Life of this patent
Estimating the term…
Abstract
In a Michelson interferometer system arranged to give four output interferograms, two at each orthogonal direction of polarization, the reflection and transmission coefficients of the interferometer beam splitter (10) at the two polarization directions are chosen so that the ratios of the a.c. component to the d.c. component are equal in three of the interferograms. Difference signals derived from the three interferograms are suitable for use with an automatic, reversible, fringe counting system.
Claims7
An improved interferometer system comprising:
- a Michelson interferometer comprising a single interferometer beam splitter and two reflecting means arranged to receive radiation from opposite sides of the beam splitter and to return radiation to the same areas of those sides whereby two exit beams of radiation are provided, one from each side of the beam splitter;
- a beam splitting and polarising means arranged to receive one exit beam and to separate the received radiation into radiation at two orthogonal directions of polarisation whereby two optical interferograms are provided;
- means arranged to receive the other exit beam and to separate from it radiation at one of said orthogonal directions of polarisation whereby a third optical interferogram is provided, the third interferogram being in phase quadrature with one of the first and second interferograms, and being in antiphase with the other of the first and second interferograms;
- characterised in that the single interferometer beam splitter has for radiation at each orthogonal direction of polarisation reflection coefficients on its two faces which are equal, and has for radiation at one orthogonal direction of polarisation a transmission coefficient which is equal to the reflection coefficient, whereby the two reflecting means each receive and return radiation having components at both orthogonal directions of polarisation.
1 more element
An improved interferometer system comprising:
- a Michelson interferometer comprising a single interferometer beam splitter and two reflecting means arranged to receive radiation from opposite sides of the beam splitter and to return radiation to the same areas of those sides whereby two exit beams of radiation are provided, one from each side of the beam splitter;
- a beam splitting and polarising means arranged to receive one exit beam and to separate the received radiation into radiation at two orthogonal directions of polarisation whereby two optical interferograms are provided;
- means arranged to receive the other exit beam and to separate from it radiation at one of said orthogonal directions of polarisation whereby a third optical interferogram is provided, the third interferogram being in phase quadrature with one of the first and second interferograms, and being in antiphase with the other of the first and second interferograms;
- said single interferometer beam splitter having for radiation at each orthogonal directional of polarisation reflection coefficients on its two faces which are equal, and having for radiation at one orthogonal direction of polarisation a transmission coefficient which is equal to the reflection coefficient;
- three photodetection means arranged to receive the three interferograms and to provide three electrical signals in the same phase relationship as the interferograms from which they are derived, and
- signal subtraction means arranged to subtract the signal pairs which are in phase quadrature, whereby two alternating output signals are provided having zero d.c. component.
3 more elements
Dependencies are inferred from the claim text.