Optical EngineeringCalibration and exploitation of a narrowband imaging polarimeter
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The integration and calibration of a narrow-band imaging po- larimeter is described. The system is designed to exploit subtle spectral details in visible and near-IR polarimetric images. All of the system components were commercial off the shelf. This device uses a tunable liquid crystal filter and a 16-bit cooled CCD camera. The challenges of calibrating a narrow-band imaging polarimeter are discussed. We describe examples of image data collected in the laboratory, which show that spectral polarimetric data is superior to unpolarized intensity data in facilitating the extraction of detail in shadowed regions below a vegetative canopy. In particular, we introduce a polarization-based normalized difference vegetation index (NDVI) algorithm that demonstrates significant contrast enhancement between a man-made object and a foilage background.