The Mueller matrix represents the most general phenomenological description of the linear interaction of an optical system or medium with polarized light.
The subject of the polarimetry theory activity is the study of the properties of theoretical as well as experimental Mueller matrices by using a formal algebraic approach.
The problem of the physical interpretation of a measured Mueller matrix is, consequently, of growing importance. In the absence of a physical model describing a given sample, its experimental Mueller matrix can still be phenomenologically interpreted by decomposing it algebraically into simpler components having a direct physical meaning.
Diattenuation (a, c) and depolarization images (b, d) of a biological sample.
The decomposition of a measured Mueller matrix into several simpler ones, representing basic polarization components (partial polarizers, wave-plates and depolarizers), often allows one to get a better insight into the physics underlying the original matrix.
The decomposition approach does not require any opticall modelling but is rather based on a general principle (physical realizability condition). Related topics of significant practical interest are:
- The determination of a non-depolarizing component out of an experimental depolarizing Mueller matrix.
- The best non-depolarizing estimate of a measured Mueller matrix.
- The best physical estimate of a measured unphysical Mueller matrix.
- The extraction of meaningful physical parameters (diattenuations, retardances, depolarization indices).
- The reduction of depolarizing matrices to canonical depolarizers allowing for a comparison of their properties.