Alternative linear microgrid polarimeters: design, analysis, and demosaicing considerations

Linear division of focal plane (DoFP), or integrated microgrid polarimeters, provide a measurement strategy for obtaining time-synchronized polarized intensity measurements across a scene. This is accomplished by masking pixels in the focal plane array sensor with a repeating pattern of different linear polarizers. The convention in industry has been to use a repeating 2×2 pattern of four linear polarizers with chosen polarizer orientation angles of {0,45,90,135}^∘. Alternative designs based upon other P×Q modulation patterns have been proposed that demonstrate improved performance over conventional microgrid arrays due to better utilization of bandwidth in the frequency domain. Here, we develop a model for linear DoFP snapshot polarimeters that provides an in-depth understanding of these devices in both the spatial and frequency domains and relate this model to previously reported generalized DoFP channeled polarimeter models. We then use the model to identify practical modulation patterns and study their performance through empirical simulations based upon data collected from real polarimeters. We demonstrate the validity of the developed model and compare the performance of the identified modulation schemes against a common set of ground truth images. We find that choosing alternative sets of polarizer angles, in conjunction with modulators that improve bandwidth usage, result in the best overall designs that can improve performance over conventional microgrid polarimeters.