**6. Complex degree of mutual polarization of laser fields formed by birefringent matrices of biological tissues. Polarimetric metrology in diagnostics of structure and physiological state of biological tissues**

Optical diagnostics of complex, inhomogeneous in phase objects, such as biological tissue (BT) includes relatively independent directions, *viz.* photometric, polarimetric and correlation. On the base of these directions, *laser polarimetry of BTs* has been formed as a new and intensively developed branch of applied optics metrology [93 - 97]. Within this branch, one considers morphological structure of BTs as two-component amorphous-crystalline structure. Crystalline component or extracellular matrix of BTs of the main types is formed by the net of coaxial cylindrical protein fibrils possessing the properties of uniaxial bireringent crystals.

Laser polarimetry has been shown to be efficient tool under single-scattering regime for finding out the set of interconnections among statistical (the first to the fourth statistical moments) and fractal (log-log dependence of power spectra) parameters, which characterize coordinate geometrical-optical structure of extracellular matrix of BT, on the one hand, and polarization parameters (coordinate distributions of the azimuth of polarization and ellipticity) at its image, on the other hand. The mentioned success in diagnostic application of laser polarimetry of optically thin BT layers stipulates further development of new statistical approaches for analysis of concordance of the states of polarization at various points of an object field formed by multy-layer BT, in part by applying the concepts of the complex degree of mutual polarization (CDMP) [6, 32, 98, 99] and determining on this base the complex degree of mutual anisotropy [100] of polycrystalline protein nets. It is of vital importance for development of new techniques for reliable estimating physiological state of optically anisotropic BTs.

Spatial modulation of correlation and polarization characteristics is intrinsic to laser radiation scattered by object fields, including images of BTs [4, 5, 93, 101 - 103]. Optical coherent tomography [104, 105] and its new branch, polarization-sensitive optical coherent tomography [95, 96, 101, 106, 107], are among the most promising techniques for obtaining information on such modulation. This diagnostic technique is based on measuring coordinate distributions of the Stokes parameters at BT images that give a possibility to obtain important data both on BT's microstructure and on magnitude and coordinate distribution of optical anisotropy of architectonic nets formed by birefringent protein fibrils. Further progress of polarization-sensitive optical coherent tomography presumes development of new techniques for polarimetric, interferometric and correlation analysis and processing of inhomogeneous in polarization images of BTs. Let us consider these techniques in more details.
