Mueller Matrix Imaging Polarimeter for UV Metrology

The University of Arizona Polarization Laboratory with support from the Jet Propulsion Laboratory (JPL) has assembled and is currently calibrating a UV Mueller matrix imaging polarmeter (UV-MMIP). The desire for more accurate polarimetric and radiometric sensors drives the need for stringent polarization requirements and the ability to more precisely measure system and component polarization behavior. One such sensor is JPL’s Multiangle Spectropolarimetric Imager (MSPI), which requires highly controlled polarization behavior from UV wavelengths to the short wave IR. The UV polarization properties of components such as broadband coated mirrors, waveplates, dichroic filters, and polarizers often behave much differently than in visible light. The UV-MMIP is designed to provide rapid and accurate determination of the complete polarization properties of components, imaged at high spatial resolution. The UV-MMIP is a dual rotating retarder polarimeter with components selected for best polarimetric precision between 250 nm and 500 nm. Polarization critical components include source, detectors, imaging optics, illumination optics, retarders, and polarizers. The back-illuminated CCD camera images at 512 x 512 pixel resolution, providing 40 micron resolution over a 2 cm field of view or as little as 1 micron resolution over a 500 micron field of view, with auxiliary UV-optimized microscope objectives. Both transmissive and reflective samples are accommodated. The entire 16-element Mueller matrix is measured on a pixel-by-pixel basis to an expected accuracy of 0.1%, matching or surpassing the accuracy of an existing visible light instrument functioning in the same laboratory. Automated data acquisition and analysis software provides detailed images of polarization characteristics including diattenuation, retardance, and depolarization.