Quantitative measurement of the anisotropy of a turbid medium using polarization imaging

Quantifying anisotropy in a turbid medium is critical for applications ranging from biomedical diagnostics to food quality assessment. Using a polarization camera and irradiation by a linearly polarized beam, we present a noninvasive method for estimating material anisotropy by analyzing depolarization ratios. To validate our approach, we perform a 3D microstructural analysis of mozzarella cheese samples to obtain ground-truth anisotropy levels using a metric based on structure tensor scale-space analysis of computed tomography (CT) scans. Our experiments with mozzarella samples of different anisotropy levels demonstrate a stronger correlation with CT-derived anisotropy and greater robustness as compared with oblique incidence reflectometry, which is limited by surface artifacts and sensitivity to sample orientation. Our method maintains high accuracy with simpler instrumentation and without sample rotation even when samples exhibit surface variations (non-flatness or texture). This establishes polarization imaging as a robust platform for noninvasive anisotropy characterization with potential applications in industrial quality control and biomedical diagnostics.