Simulation of practical single-pixel wire- grid polarizers for superpixel stokes vector imaging arrays

An optical tracking sensor that produces images containing the state of polarization of each pixel can be implemented using individual wire-grid micropolarizers on each detector element of a solid-state focal plane array. These sensors can significantly improve identification and tracking of various man-made targets in cluttered, dynamic scenes such as urban and suburban environments. We present electromagnetic simulation results for wire-grid polarizers that can be fabricated on standard imaging arrays at three different technology nodes (an 80-, 250-, and 500-nm pitch) for use in polarization-sensitive detector arrays. The degradation in polarizer performance with the larger pitch grids is quantified. We also present results suggesting the performance degradation is not significant enough to affect performance in a man-made vehicle-tracking application. 1 Introduction Optically locating and following a moving target through a cluttered environment is a challenging task. Target detection and tracking can be made much more robust by exploiting specific signatures of an artificial target relative to a natural background, such as spectral characteristics 1 (via multispec-tral and hyperspectral imaging) or polarization state. 2–4 A single linear polarizing element in the input optics of a detector system can be rotated to enable collection of the complete Stokes vector describing the polarization state of each pixel in an image, but this is only practical for slow-moving or static scenes. 2,5 For rapid data collection of fast-moving scenes at video rates, the Stokes vector of the entire scene must be collected coincidentally. This can be accomplished by simultaneously collecting three polarization images for each pixel at 0, 60, and 120 deg linear polarization, for example.