Mueller polarization imaging can obtain all the polarization information closely related to the microscopic structure and composition of a sample through multiple measurements. The reflective Mueller microscope can effectively detect the microscopic structure of large samples and monitor dynamic changes in live animals. These applications place high demands on the speed, accuracy, and stability of detection. Traditional reflective microscopes are mostly based on the dual-rotating waveplate method and the liquid crystal modulation method. The dual-rotating waveplate method, however, involves mechanical rotation, which leads to slow measurement speeds and difficulties in ensuring accuracy. While the liquid crystal modulation method provides faster single measurements, it still requires 16 measurements to obtain the sample’s Mueller matrix. Some researchers have proposed a dual-polarization-camera configuration, which requires only 4 measurements to obtain the Mueller matrix, but this approach introduces structural complexity and issues related to multi-detector registration. Therefore, a simplified reflective Mueller microscope is proposed, which not only ensures faster detection speeds but also maintains accuracy and stability—key factors for the application of reflective Mueller microscopes.

Considering the advantages and disadvantages of various configurations in existing reflective Mueller polarimeters, we propose a reflective Mueller microscope combining a polarization camera and liquid crystal variable phase retarders. In the configuration of the polarization state analyzer, the instrument uses a polarization camera and a liquid crystal phase retarder, which requires only two measurements to obtain the Stokes vector of the sample’s backscattered light. The polarization state generator is composed of a polarizer and dual liquid crystal phase retarders. With this configuration of the polarization state generator and analyzer, the instrument achieves the detection of the sample’s Mueller matrix with just 8 measurements. This reduces the number of measurements required while maintaining a simple instrument structure. The use of liquid crystal variable phase retarders also increases the speed of single measurements and eliminates mechanical motion. To improve the stability of the instrument, we consider the polarization characteristics of all polarization modulation and imaging devices within the instrument, optimizing the measurement parameters for optimal performance. To further improve measurement accuracy, the instrument calibrates after eliminating stray light during the measurement process. The detection accuracy and stability of the instrument are verified through testing with standard polarization samples. Finally, the instrument is successfully applied to imaging the dehydration process of bovine tendon tissue, which demonstrates its significant potential and application value in the biomedical field, particularly in tissue imaging.

The optimization of the instrument matrix begins by first obtaining the Mueller matrix of the non-polarizing modulation devices through a multi-step eigenvalue calibration method. Then, the corrected actual instrument matrix model is obtained by combining the Mueller matrix of the polarization modulation devices. Finally, based on this model, the optimal measurement parameters are optimized for the polarization state generator (Table 1) and the polarization state analyzer (Fig. 2). The instrument’s measurement of the Mueller matrix for the mirror indicates that the detection error of the calibrated instrument is not more than 0.0017 (Fig. 3). Through continuous measurement of the 1/8-wave plate placed on the mirror for 1 h, the instrument demonstrates high temporal stability (Fig. 4), with a standard deviation of 0.0067°. Finally, the instrument is successfully applied to imaging the dehydration process of bovine tendon tissue (Fig. 5). As the tissue dehydration progresses, the retardance of the sample gradually increases. This is mainly because, after dehydration, the structural density of the tendon fibers increases, which leads to enhanced birefringence of the sample. The depolarization images of the sample gradually reveal a more pronounced texture, which is closely related to changes in the sample’s shape and local structural density. This demonstrates that the microstructural changes in bovine tendon tissue during dehydration can be observed through retardance and depolarization images.

We present a reflective Mueller microscope with a hybrid configuration of a polarization camera and liquid crystal variable phase retarders, which requires only 8 measurements to obtain the Mueller matrix of the sample. After considering the polarization characteristics of all the devices in the instrument, the optimal measurement parameters are determined. The performance of the calibrated instrument is validated using standard polarization elements. The measurement results for the mirror indicate that the instrument’s measurement accuracy is better than 0.0017, while the results from continuous measurements of the waveplate over one hour demonstrate the instrument’s strong temporal stability. Finally, the instrument is applied to image the dehydration process of bovine tendon tissue, with clear observation and analysis of the changes in the tissue’s polarization characteristics due to dehydration. This demonstrates that the instrument can be used for dynamic monitoring of microstructural changes in tissues, thus providing an effective tool for biomedical research.