This article addresses the estimation of polarization signatures in the Mueller imaging framework by non-local means filtering. This is an extension of previous work dealing with Stokes signatures. The extension is not straightforward because of the gap in complexity between the Mueller framework and the Stokes framework. The estimation procedure relies on the Cholesky decomposition of the coherency matrix, thereby ensuring the physical admissibility of the estimate. We propose an original parameterization of the boundary of the set of Mueller matrices, which makes our approach possible. The proposed method is fully unsupervised. It allows noise removal and the preservation of edges. Applications to synthetic as well as real data are presented.
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http://dx.doi.org/10.1364/OE.21.004424 | DOI Listing |
Chem Biomed Imaging
April 2024
School of Precision Instruments and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, China.
Medium depolarization imaging by catheter-based polarization-sensitive optical coherence tomography (PS-OCT) can provide valuable insight into significant features of lipid, macrophages, and cholesterol crystals in atherosclerotic vulnerable plaques. In this paper, we demonstrate a method to achieve an accurate estimation of the medium depolarization index (EMDI) with noise immunity in catheter-based PS-OCT. EMDI is calculated by an iterative approximation based on Lu-Chipman matrix decomposition and Frobenius norm judgment of incoherent averaging of Mueller matrices.
View Article and Find Full Text PDFMueller matrices provide a complete description of a medium's response to excitation by polarized light, and their characterization is important across a broad range of applications from ellipsometry in material science to polarimetry in biochemistry, medicine and astronomy. Here we introduce single-shot Mueller matrix polarimetry based on generalized measurements performed with a Poincaré beam. We determine the Mueller matrix of a homogeneous medium with unknown optical activity by detecting its optical response to a Poincaré beam, which across its profile contains all polarization states, and analyze the resulting polarization pattern in terms of four generalized measurements, which are implemented as a path-displaced Sagnac interferometer.
View Article and Find Full Text PDFLocal phase retardation (LPR) is increasingly recognized as a crucial biomarker for assessing disease progression. However, the presence of speckle noise significantly challenges its accuracy and polarization contrast. To address this challenge, we propose a signal-processing strategy aimed at reducing the impact of noise on LPR measurements.
View Article and Find Full Text PDFBioinformatics
June 2024
Department of Biomedical Engineering, Florida International University, West Flagler Street, Miami, FL 33174, USA.
Motivation: Imaging Mueller polarimetry has already proved its potential for biomedicine, remote sensing and metrology. The real-time applications of this modality require both video rate image acquisition and fast data post-processing algorithms. First, one must check the physical realizability of the experimental Mueller matrices in order to filter out non-physical data, ie to test the positive semi-definiteness of the 4 × 4 Hermitian coherency matrix calculated from the elements of corresponding Mueller matrix pixel-wise.
View Article and Find Full Text PDFWe present reciprocal polarization imaging for the optical activity of chiral media in reflection geometry. The method is based on the reciprocal polar decomposition of backscattering Mueller matrices accounting for the reciprocity of light waves in forward and backward scattering paths. Anisotropic depolarization is introduced to gain sensitivity to optical activity in backscattering.
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