White light Sagnac interferometer polarimeters
AssigneeArizona Board of Regents on Behalf of the University of Arizona
InventorMichael W. Kudenov
Life of this patent
Estimating the term…
Abstract
Snapshot imaging polarimeters comprise Sagnac interferometers that include diffraction gratings situated to produce shear between counter-propagating optical fluxes produced by a polarizing beam splitter. The counter-propagating, sheared optical fluxes are focused onto a focal plane array to produce fringe patterns. The fringe patterns correspond to a scene polarization distribution modulated onto a spatial carrier frequency associated with a diffraction order. Multi-blazed gratings can be used so that modulations at a plurality of spatial frequencies are produced, with each spatial frequency corresponding to a spectral component of an input optical flux. Modulated fringe patterns can be demodulated to obtain scene Stokes parameter distributions.
Claims19
An apparatus, comprising:
- a Sagnac interferometer that includes a pair of diffraction gratings so as to produce a dispersion compensated shear between first and second portions of an input light flux, the Sagnac interferometer comprising a polarizing beam splitter that directs the first and second portions of the input light flux along respective interferometer optical paths to the pair of diffraction gratings;
- a polarization analyzer situated to receive a combination of the sheared first and second portions of the input light flux and produce an associated output light flux;
- a detector situated to receive the output light flux and produce an image signal;
- and
- an image processor that produces a polarization image based on the image signal.
A method, comprising:
- receiving an input optical flux;
- directing first and second portions of the input optical flux along optical paths in a Sagnac interferometer with a polarizing beam splitter;
- diffracting each of the first and second portions of the input optical flux at at least one diffraction grating so as to produce a shear having a magnitude associated with a grating period and diffraction order and that is proportional to a wavelength of the input optical flux;
- and
- estimating a polarization characteristic of the input optical flux based on a spatial frequency associated with the shear in an intensity pattern obtained by directing the sheared first and second portions to a polarization analyzer and combining the sheared, polarization analyzed first and second portions of the input optical flux.
A polarimeter, comprising:
- a Sagnac interferometer defined by a polarizing beam splitter, first and second diffraction gratings and associated first and second reflectors, such that first and second polarization components of an optical flux directed to the polarization beam splitter counter-propagate from the polarizing beam splitter, the first polarization component propagating to the first grating, the first reflective surface, the second reflective surface, the second grating, and the polarization beam splitter, and the second polarization component propagating to the second grating, the second mirror, the first grating and to the polarization beam splitter, wherein the Sagnac interferometer produces a shear between first and second counter-propagating polarization components that is a function of at least one of diffraction grating period, diffraction order, separation of diffraction gratings and respective reflective surfaces, and separation of the first and second reflective surfaces;
- a focusing element that combines the counter-propagating portions of the input optical flux to produce an intensity pattern;
- a polarization analyzer situated to receive the combined counter-propagating portions of the input optical flux so that the intensity pattern is based on the combined, polarization analyzed, counter-propagating portions of the input optical flux;
- a detector that receives the intensity pattern and produce a detected intensity pattern;
- and
- an image processor that produces a polarization image based on the detected intensity pattern.
Dependencies are inferred from the claim text.