# Review on Complete Mueller Matrix Optical Scanning Microscopy Imaging
## 3 Mueller Matrix Applications
### Ophthalmology  
As presented in the last section, the main application of MM microscopy using SLM was devoted to ophthalmology. The main reason comes from the desire in finding an alternative approach for diagnosing any pathology at rate faster than the eye motion similar to earlier methods proposed by OCT imaging. Moreover, coupling with additional signal processing, MM offers the reduction of the exposure time that limit the damage through the \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Num. of Scan** & **Speed** & **Advantages** & **Disadvantages** \\ \hline Single detection & 16 & few mins & Simple calibration & Precise alignment \\  & & & Cheap & Active elements \\  & & & & Succesive scans \\  & & & & Post processing \\ \hline Multiple detection & 4 to 8 & 50 ms to 10 s & Snapshot detection & Precise alignment \\  & & & Cheap & Succesive scans \\  & & & & Heavy calibration \\  & & & & Spacy \\ \hline Spectral detection & 1 & 10 \(\mu\)s & Snapshot & Precise alignment \\  & & & Compact & Heavy calibration \\  & & & Passive elements & Complex modeling \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Main performances and capabilities of the single and multiple channel temporal MM acquisition (two first lines) comparing to the spectral detection for recovering the full Mueller matrix image. The number of scan reported in the first column referred to the minimal number for retrieving the the 16 elements of the MM image. The speed referred to the lowest one for the method reported in the literature. Figure 4: Comparative acquisition speed for measuring the full MM images using the sequential/spectral approaches according to the optical SLM architecture presented in the literature. eye. Besides, it has been shown that in presence of pathology, the disorganization of thick tissues exhibits strong modification in the birefringence and depolarization and MM has the capability of quantifying these parameters. This explains that most of the incomplete MM microscopes tends to track these only two parameters reducing the number of information but accelerating the process for encoding/decoding the polarization states [68,69]. First, because the ocular media and the retina in the human eye exhibit rather complicated polarization properties, every technique based on collecting the light scattered back into the retina in double pass is affected by polarization. Second, another challenge for such a system is the fast motion and optical properties in the living eye, required a high speed rate encoding/decoding of the polarization states. Third, to avoid any damage, the wavelength should be chosen wisely so as to reduce the radiation exposition and limit the absorption that participates in reducing drastically the polarimetric SNR. Some images obtained in the SLM configuration for MM are presented Figure 5.  
Figure 5: Quantitative imaging of the full Mueller matrix for opthalmology applications. (**a**) Degree of polarization images of the retina for two different size of pupil. (**b**) Polarization parameter images of the optical nerve head. These images corresponds to the normalized average intensity m00; linear retardance—RL; retardance orientation \(\alpha_{R}\); depolarization index Dep; diattenuation D; diattenuation orientation \(\alpha_{D}\). and (**c**) Quantitative analysis of a rat cornea polarization resolved image. Top two rows correspond to images at 10 and 70 \(\upmu\)m depth while bottom row shows 3D volume of Second Harmonic Generation (SHG) and Two-Photon Excitation Fluorescence (TPEF), and percent change. Adapted with permission from: (**a**) [44]; (**b**) [49]; (**c**) [52], © The Optical Society. One of the first application of MM has been proposed in 2000 that studied the influence of the eye pupil size on the birefringence [70]. For limiting the exposure time but acquiring a high number of image, the number of pixel is quite small.