Dual division of focal plane polarimeters-based collinear reflection Mueller matrix fast imaging microscope

Fast and high-accuracy collinear reflection Mueller imaging polarimeter implemented with the compound calibration method

The collinear reflection Mueller matrix imaging polarimeter is suitable for characterizing thick samples with high-scattering depolarization such as biological tissues or in-situ living organs. Achieving fast detection and high measurement accuracy is vital to prevent artifacts and accurately assess polarization characteristics in these applications. This paper demonstrates a fast collinear reflection imaging polarimeter based on liquid crystal variable retarders (LCVRs-CRMMIP). We propose a novel compound calibration method (CCM), to the best of our knowledge, which enhances measurement accuracy through light intensity correction and an improved equivalent calibration sample model. This method surpasses the double-pass eigenvalue calibration method (dp-ECM), enhancing accuracy by over 23 times. Performance evaluations with standard samples, including mirrors, linear polarizers, and wave plates, reveal that the LCVRs-CRMMIP achieves rapid measurements (about 3 s) and high accuracy with an error of less than 0.0017.

Error analysis and optimization for a full-Stokes division-of-space polarimeter

A generalized four-channel, full-Stokes division-of-space (DoSP) error propagation model and its version with a reference optical path are presented in this paper, covering all potential error sources such as the main detector noise, intensity fluctuations, and instrument matrix error. Based on the model, a classical division-of-amplitude polarimeter (DoAmP) structure consisting of a partially polarized beam splitter (PPBS), PBS, and wave plates is thoroughly evaluated. By optimizing the PPBS and azimuth of the wave plates, several optimal parameter configurations are identified where the condition number is 1.84, and the maximum wavelength deviation range is limited to (-3.4n m, 3.62 nm), where the degree of polarization and polarized angle errors do not exceed 0.03 and 0.3°, respectively, and the instrument matrix deterioration effect is minimal enough to be disregarded. In addition to the DoAmP structure, this error propagation model can be directly extended to other arbitrary four-channel DoSP structures such as division-of-focal-plane and division-of-aperture systems, which have guidance values for system structural design, error optimization, and discovering multi-wavelength compatibility of the instrument.

Mueller matrix imaging of pathological slides with plastic coverslips

Mueller matrix microscopy is capable of polarization characterization of pathological samples and polarization imaging based digital pathology. In recent years, hospitals are replacing glass coverslips with plastic coverslips for automatic preparations of dry and clean pathological slides with less slide-sticking and air bubbles. However, plastic coverslips are usually birefringent and introduce polarization artifacts in Mueller matrix imaging. In this study, a spatial frequency based calibration method (SFCM) is used to remove such polarization artifacts. The polarization information of the plastic coverslips and the pathological tissues are separated by the spatial frequency analysis, then the Mueller matrix images of pathological tissues are restored by matrix inversions. By cutting two adjacent lung cancer tissue slides, we prepare paired samples of very similar pathological structures but one with a glass coverslip and the other with a plastic coverslip. Comparisons between Mueller matrix images of the paired samples show that SFCM can effectively remove the artifacts due to plastic coverslip.