Mueller matrix BRDF measurements using random sampling and fiber-coupled detectors

The bidirectional reflectance distribution function (BRDF) of surfaces has deleterious effects on optical measurements. Collecting Mueller matrix BRDF (mmBRDF) measurements of a surface by conventional goniometric techniques can be time-consuming. We present a system for collecting mmBRDF measurements using optical fiber detectors that sample the hemisphere surrounding an object. The entrance to each fiber contains a polarization state analyzer (PSA) configuration which allows for the simultaneous acquisition of the Stokes vector at many altitudinal and azimuthal viewing positions. We describe the setup, calibration, and data processing for this system and present its performance as applied to mmBRDF measurements of maize leaves.