Micro-scale surface and contaminate modeling for polarimetric signature prediction

Abstract

The optical properties of a surface may change significantly in response to contaminants from the environment and/or human activity. We utilize a first principles, physics-based radiometric ray tracing software package to evaluate the spectral polarimetric bi-directional reflectance distribution function (p-BRDF) of the virgin and contaminated surfaces. In the absence of contaminants and allowing only single bounces, we find the simulated reflectance properties of randomly rough Gaussian surfaces to be well represented by micro-facet based p-BRDF analytical models. However the addition of contaminants introduces phenomenology that falls outside the basic assumptions of the micro-facet analytical p-BRDF models. We will present initial results of p-BRDF simulations of random Gaussian surfaces with liquid contaminants.

Parameter-based imaging from passive multispectral polarimetric measurements

“…However, if the illumination polarization is known, the extension of the analysis to this case is relatively straightforward. We note that the fourth Stokes component, corresponding to the circular polarization state, is not measured by the Ground-MSPI due to its insignificant contribution in most natural scenes [1][2]4,[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22].…”

“…For this work we separate scattering phenomena into two general categories: surface and diffuse [9][10][11][12][13][14]. Surface scattering occurs at the interface between air and the target surface.…”

“…We assume the diffuse scattering is completely unpolarized and Lambertian where the light encounters enough multiple scattering events within the bulk of the material that the scattering directions and polarization state are uniformly random. In general, the diffuse scattering may exhibit some polarization and directional preference due to the re-emergence processes [23], but the assumptions of unpolarized and Lambertian scattering are reasonable especially for remote sensing scenarios where the target's surface roughness is typically large compared to the incident wavelength [9][10][11][12][13][14][15][16][17][18][19][20][21][22]. In contrast, the surface scattering that develops based on a microfacet model, can produce a directional lobe and polarization preference.…”

“…Gartley et al [9] and Litvinov et al [10] modified the microfacet pBRDF by introducing several coefficients to account for the depolarization behavior. The coefficient values are determined by fitting the model to measured data but the development of the coefficients was not specifically physics-based.…”

“…The formulation of ρ DHR suggests it is difficult to measure directly and estimating surface parameters using the associated model could be problematic for remote sensing applications [12]. We also note that the previous work cited in [7][8][9][10][11][12] addresses a fixed point on the surface of interest and the evaluations are limited to indoor laboratory measurements.…”