As an emerging powerful tool to provide structural information of tissue specimens label-freely, Mueller matrix (MM) polarimetry has garnered extensive attention in biomedical studies and pathological diagnosis. However, for the commonly used constant-step rotating MM polarimetric system, beam drift induced by the rotation of polarization elements can lead to distortions in measurement results, severely affecting MM imaging accuracy. Here, based on our previous study, we propose an optimized self-registration method to mitigate the pseudo-depolarization effects introduced by image artifacts in constant-step rotating MM polarimetry. By addressing the prevalent issue of beam drift and image distortions in such polarimetric imaging systems, the effectiveness of the proposed method is experimentally validated using tissue samples. The results demonstrate a significant enhancement in the accuracy of depolarization parameter estimation after applying the optimized self-registration method. Furthermore, the method enhances the coarseness and contrast of MM-derived parameters images, thereby bolstering their capacity to characterize tissue structures. The optimized self-registration method proposed in this study can provide an innovative approach for quantitative tissue polarimetry based on constant-step rotating MM measurement, and contribute to the advancement of polarimetric imaging technology in biomedical applications.

Mueller matrix polarimetry is recently attracting more and more attention for its diagnostic potentials. However, for prevalently used division of time Mueller matrix polarimeter based on dual-rotating retarder scheme, beam drift induced by rotating polarizers and waveplates introduces spatial misalignment and pseudo-edge artifacts in imaging results, hindering following accurate microstructural features characterization. In this paper, we quantitatively analyze the beam drift phenomenon in dual-rotating retarder Mueller matrix microscopy and its impact on linear retardance measurement, which is frequently used to reflect tissue fiber arrangement. It is demonstrated that polarizer rotation induces larger beam drift than waveplate rotation due to surface non-uniformity and stress deformation. Furthermore, for waveplates rotated constantly in dual-rotating retarder scheme, their tilt within polarization state analyzer can result in more drift and throughput loss than those within polarization state generator. Finally, phantom and tissue experiments confirm that beam drift, rather than inherent optical path changes, dominates the systematic overestimation of linear retardance in boundary image regions. The findings highlight beam drift as a dominant error source for quantifying linear retardance, necessitating careful optical design alignment and a reliable registration algorithm to obtain highly accurate polarization data for training machine learning models of pathological diagnosis using Mueller matrix microscopy.