Research On The Validity Of Mueller Matrix Decomposition Method And Influence Of Optical Absorption Effect

Polairzation imaging technology has shown powerful application prospect in the field of biomedical optics.Measuring the polarization property of tissues,such as the Mueller matrix and extracting the corresponding characteristic parameters can help us understand the propagation of polarized light in tissues and then analyze the samples' microstructure and optical properties.In this thesis,we first presented two kinds of parameter extraction methods,one is linear polarization Mueller matrix decompositon method for 3× 3 Mueller matrix,the other is complete Mueller matrix decompositon method for 4× 4 Mueller matrix.Linear Mueller matrix decomposition method only requires 9 linear polarization measurements,thus significantly simplifying its polarization imaging system and making it possible to combine with multi-spectral technology.The complete Mueller matrix decomposition method requires at least 16 polarization measurements involving both linear and circular polarizaition components,but this method can obtain the complete polarization information and has a wider using range.Based on our previous Monte Carlo simulation for sphere-cylinder birefringence model and tissue phantom experiment,we analyzed the validity and limitation of linear polarization Mueller matrix decomposition method.We started from the isotropic spherical scattering system and then analyzed the anisotropic system caused by birefringence of the medium and cylindri cal scattering process.The simulated and experimental results show that the depolarization and linear retardance obtained from the 3× 3 and 4× 4 Muller matrix are usually not the same quantitatively,but display similar qualitative relations to changes in the microstructure of samples.Additionally it should be noted that the decomposition of 3× 3 Mueller matrix for spheres can generate a singularly higher linear retardance.Finally these results are also backed up by simulations and experiments in the backward scattering direction.All these analysis supported the limitation of linear polarization Mueller matrix decomposition method in quantitative physical characterization and its feasibility in qualitative imaging recognition.In this thesis,we also extended the sphere-cylinder birefringence model to include the absorbing effect in the ambient mediuim or on the scatterers by making the absorbing coeffici ent of the medium or the imaginary part of the refrative index of scatterers adjustable.These two optical settings can give a better description of absorption effect among cells or on tissue organs for our tissue models.We started with one-component model and gradually transfered to multi-component model.Using complete Mueller matrix decomposition method,we analyzed the changing trends of diattenuation ? depolarization and linear retardance in different absorption effects.The results indicated that the absorption effect in the ambient medium influences the decomposition parameters monotonously.For example it enhances diattenuation but depresses the depolarization and cylinder-scattering induced retardance.However the absorption effect on the scatterers influences the decomposition parameters nonmonotonously.For the retardance coming from the birefringence of the ambient medium,both of the two kinds of absorption effect make no difference.An explanation based on the changes of photon scattering behavio r caused by absorption effect was provided finally.