Automated Measurement Of Polarized Bidirectional Reflectance For Qualification Of Minerals And Oxide Coatings

An Automated Bidirectional Reflectance Measurement System (ABRAMS) has been constructed to facilitate measurement of polarized bidirectional reflectance from soil and vegetative samples in the laboratory. The system illuminates a sample with linearly-polarized laser light of wavelength h=632.8 nm, and is capable of synchronously detecting both the likeand crosspolarized scattered intensities at discrete angles spanning half a hemisphere. The measured scattering coefficient and bidirectional reflectance factor for both like and cross polarizations are shown for several particulate samples in the backscattering and forwardscattering directions. In particular, samples of uncoated quartz (translucent) and pyrolusite-coated quartz (opaque) exhibited high and low, respectively, levels of cross polarization. Results indicate that polarization information in the plane of incident is useful for inferring characteristics regarding the surface and volume of a target. A high level of cross polarization, for example, indicates that significant multiple scattering is occurring; this is due primarily to the volume of the target since surface depolarization effects are minimal in the plane of incidence.