White-light Sagnac interferometer for snapshot polarimetric and multispectral imaging

A common technique, referred to as channeled imaging polarimetry (CIP), enables the snapshot acquisition of the 2- dimensional Stokes parameters of an arbitrary scene or sample. It achieves this by amplitude modulating the Stokes parameters onto various interference-based spatial carrier frequencies. While this technique has utility, it often suffers from low signal-to-noise ratios in remote sensing scenarios, since it requires narrow spectral bandwidth illumination (< 3 nm in the visible). This paper discusses one hardware implementation that can be utilized to overcome this limitation. Consequently, an overview of the theoretical and experimental development of this system, a uniquely modified Sagnac interferometer, is discussed. Both laboratory and outdoor data are included to demonstrate the instrument's ability to measure polarization in arbitrary scenes. Inclusion of blazed diffraction gratings inside the interferometer enables whitelight interference fringes to be generated. By incorporating these gratings, the operational bandwidth of the interference fringes can exceed approximately 300 nm within the visible spectrum; two orders of magnitude greater than previous CIP implementations. Lastly, by modifying the diffraction grating, the sensor becomes capable of snapshot multispectral imaging. This is briefly discussed, with both a theoretical description and experimental data.