April 16, 2014, Wednesday, 105

Hyperspectral Imaging Polarimetry

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Extraction of spectral and polarimetric information from the image
Extraction of spectral and polarimetric information from the image

Contents

Project Summary

The overall goal of this proposal is to build and develop snapshot imaging spectropolarimeter that will be extremely convenient, and permit us to measure spectral and polarization information of the dynamic events with no moving or tunable parts by using the liquid crystal diffraction grating, polarization grating (PG).

Motivation for Approach

Imaging Spectropolarimeter utilizing Polarization Gratings
Imaging Spectropolarimeter utilizing Polarization Gratings

The spectral information is important to identify material properties while the polarization information is essential to determine the surface and shape of the objects. Measurements of the both spectral and polarization information are used in various fields including astronomy, remote sensing, and biomedical imaging/diagnosis. However, most systems are still specialized either for the spectrometry or polarimetry. The most recent technique for a simultaneous acquisition of both contents requires sequential detection using its moving parts or needs modulation process which leads to significant time consuming and reduces sampling resolution. Using the PGs, however, we can detect full spectral and polarization information on a two dimensional space without any moving parts or any modulation process. Since the spatially varying birefringence pattern of a PG leads to the imaging spectrum from the angular dispersion and polarization separation from the order of diffraction, the use of multiple PGs makes it possible to project spectral and polarization information with the two dimensional dispersion patterns. Moreover, some of the existing technologies cannot be applied for dynamic circumstance due to their lack of snapshot capability. Other systems can get a snapshot detection analyzing diffraction patterns which come from hologram disperser, but they lose the image resolution in Stokes spectra and are time consuming since they need a modulation process for extracting polarization information of the image. Our proposed imaging spectropolarimeter is uniquely compelling as it provides snapshot capability and polarization separation capability on the single detector. Comparing with other technologies, our new system has powerful potential for attaching to the conventional imaging systems due to the robust, compact and lightweight properties of our design.

Anticipated Benefits

This work are expected to further advance research in the imaging technology using optical elements. Our Polarization Grating Imaging Spectropolarimeter (PGIS), with a real-time image acquisition, would have major impact on all areas of life where there is a need for such technology, including Medical Imaging/Diagnosis, Biology, Military and so on.

Project Publications

  • J Kim and MJ Escuti, "Snapshot imaging spectropolarimeter utilizing polarization gratings," Proc. SPIE, vol. 7086, art. no. 708603, 2008.

Background References

Polarization Gratings (PGs)

  • L. Nikolova and T. Todorov, "Diffraction efficiency and selectivity of polarization holographic recording," Opt. Acta, vol. 31, 579-588 (1984).
  • J. Tervo and J. Turunen, "Paraxial-domain diffractive elements with 100% efficieincy based on polarization gratings," Opt. Lett., vol. 25, 785-786 (2000).
  • H. Lajunen, J. Tervo, and J. Turunen, "High-efficiency broadband diffractive elements based on polarization gratings," Opt. Lett., vol. 29, 803-805 (2004).

Spectropolarimetry

  • M.J. Escuti et al., Simplified spectropolarimetry using reactive mesogen polarization gratings, Proc. SPIE, Vol. 6302 (2006).
  • C.T. Willoughby et al., Application of hyperspectral imaging spectrometer systems to inductrial inspection, Proc SPIE, Vol. 2599, pp. 264-272 (1996).
  • J. S. Tyo, D. L. Goldstein, D. B. Chenault, and J. A. Shaw, "Review of passive imaging polarimetry for remote sensing applications," Appl. Opt. 45, 5453-5469 (2006).