We measure the Mueller matrix bidirectional reflectance distribution function (BRDF) of pressed and sintered powdered polytetrafluoroethylene (PTFE) reflectance standards for an incident angle of 75°. Rotationally averaged Mueller matrices from the materials showed a small asymmetry M12 .ne. M21 and M34 .ne. −M43 in the in-plane geometry. This asymmetry, however, followed Helmholtz reciprocity rules. A significant anisotropy was observed in the sintered samples, which was manifested as non-zero off-block diagonal elements that depended upon rotation of the samples. Modeling using a Mueller matrix extension to the radiative transfer equation was performed. While there was not quantitative agreement, some aspects of the data were observed, including the asymmetry. Availability of an improved Mueller matrix phase function should improve the quality of the model-experiment agreement.
Proceedings Title: Polarization Science and Remote Sensing V
Conference Dates: August 21-22, 2011
Conference Location: San Diego, CA
Pub Type: Conferences
BRDF, Mueller matrix, PTFE, reflectance standards