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.

Mueller matrix imaging with a spatially modulated polarization light source.

In this paper, we present a Mueller matrix imaging system consisting of a spatially modulated polarization light source (SMPL) and a dual division-of-focal-plane (DoFP) polarimeters as the PSA and 2D detector. The system does not contain moving parts such as a rotating stage, which leads to more robust and reliable operations for applications in hostile settings. By taking Muller matrix images at variable distances between the SMPL and the target, we examine in details errors due to different spatial distributions in angle and intensity of different polarized lights. A calibration method is proposed to reduce such errors introduced by SMPL. The performances of the new imaging technique and the calibration method are tested in Mueller matrix imaging of different samples.