Ultra-compact snapshot imaging fourier transform spectrometer

1. An interferometer, comprising, from object-wise to image-wise along an axis:

a lens array that produces a plurality of sub-images of an object based on associated sub-image light fluxes;

a polarizing grating situated to produce an interference pattern in the sub-image light fluxes having a wavelength independent spatial frequency that is associated with a period of the polarizing grating;

a birefringent prism that produces a spatially varying optical path difference (OPD) between orthogonal polarization states associated with the sub-image light fluxes;

a polarization analyzer situated to project at least a portion of orthogonal polarization states of the sub-image light fluxes to a common polarization state;

an array detector situated to receive the projected sub-image light fluxes; and

a processor coupled to the array detector that produces a spectral image based on calculations using portions of the sub-image light fluxes associated with the wavelength independent spatial frequency.

2. The interferometer of claim 1 , wherein the birefringent prism is a Wollaston prism so as to produce an OPD that varies linearly along a wedge direction.

3. The interferometer of claim 2 , further comprising an input polarizer situated to receive light fluxes associated with the sub-images from the object, wherein the input polarizer is oriented to polarize the light fluxes so that at least a portion of the polarized light flux is associated with ordinary ray propagation and extraordinary ray propagation in the Wollaston prism.

4. The interferometer of claim 3 , wherein the birefringent prism includes a first Wollaston prism and a second Wollaston prism, and further comprising a half-wave retarder situated between the first and second Wollaston prisms and oriented so as to exchange polarization directions for the sub-image light fluxes received from the first Wollaston prism and directed to the second Wollaston prism.

5. The interferometer of claim 4 , wherein the first and second Wollaston prisms are situated so as to be fringe localization compensated (FLC) prisms.

6. The interferometer of claim 1 , wherein the birefringent prism includes a first prism pair and a second prism pair, wherein the first and second prism pairs are situated so as to be fringe localization compensated (FLC) prisms.

7. The interferometer of claim 6 , wherein the prism pairs are Nomarski prisms or Wollaston prisms.

8. The interferometer of claim 1 , further comprising a processor coupled to store recorded sub-images based on the sub-image light fluxes received at the array detector and process the recorded sub-images to produce a spectral image.

9. The interferometer of claim 8 , wherein the processor produces the spectral image based on a Fourier transformation of the recorded sub-images.

10. A spectral imaging method, comprising:

directing a plurality of sub-image light fluxes associated with an object to a birefringent prism so as to produce optical path differences between orthogonal states of polarization of the sub-image light fluxes;

transmitting the sub-image light fluxes with the optical path differences to a polarization analyzer;

processing the sub-image light fluxes with at least one polarization grating to produce a wavelength-independent spatial frequency in sub-image light flux interference patterns;

recording intensity patterns based on the polarization analyzed sub-image light fluxes; and

processing the recorded intensity patterns so as to produce a spectral image of the object based on calculations using the wavelength independent spatial frequency.

11. The method of claim 10 , wherein the birefringent prism is configured to provide a spatially varying optical path difference between the orthogonal states of polarization.

12. The method of claim 11 , wherein the birefringent prism is one or more Wollaston prisms or Nomarski prisms.

13. The method of claim 10 , further comprising polarizing the sub-image light fluxes and directing the polarized sub-image light fluxes to the birefringent prism.

14. The method of claim 10 , wherein the sub-image light fluxes correspond to sub-images of the object produced by a lens array.

15. A spectral imaging apparatus, comprising, along an axis from an object:

a lens array that produces a plurality of sub-images of an object associated with sub-image light fluxes;

a polarization generator that polarizes the sub-image light fluxes;

a birefringent prism pair situated to receive the polarized sub-image light fluxes such that the sub-image light fluxes propagate in the birefringent prism pair in at least two eigenpolarizations;

a quarter wave retarder situated to receive the sub-image light fluxes from the birefringent pair and produce corresponding circularly polarized light fluxes;

a first polarization grating situated to receive the circularly polarized light fluxes and produce corresponding diffracted light fluxes;

an array detector configured to record the diffracted light fluxes; and

a processor that produces a spectral image based on a Fourier transform of the diffracted light fluxes such that the spectral image is calculated based on detected portions of the recorded diffracted light fluxes associated with a spatial heterodyne frequency based on a period of the polarizing grating.

16. The spectral imaging apparatus of claim 15 , further comprising a second polarizing grating, wherein the first and second polarizing gratings are situated so that the spatial heterodyne frequency is based on a product of the periods of the first and second polarizing gratings.