Polarization-probe polarization-imaging system in near-infrared regime using a polarization grating

A polarization-probe polarization-imaging (PPPI) system was developed for the near-infrared (NIR) regime. This system comprises two components operating as a polarization generator and a polarization analyzer to enable polarization image capture under polarized light illumination. The captured polarization images contain considerable object information because the illuminating polarized light beams are affected by many of the Mueller matrix elements. By assembling the polarization camera using two liquid crystal retarders and a polarization grating, the PPPI system offers the potential to measure the Stokes parameters fully with a high extinction ratio, even in the NIR region. The PPPI system's feasibility was demonstrated experimentally. Its dependence on the state of polarization (SoP) of the illuminating polarized light was discussed. The polarization image acquired by the PPPI system is strongly dependent on the illuminating light's SoP, so the appropriate SoP must be selected for each object to enhance the polarization image contrast. This PPPI system should expand the range of polarization imaging applications, including LiDAR, product inspection, and bio-imaging.