Simulation And Experimental Methods Of Backscattered Mueller Matrix For Discrimination Of Optical Property In Turbid Media

Polarized property of turbid media can be well described by Mueller matrix. In this thesis the propagation of polarized light in turbid media was discussed using Stokes-Mueller formalism, Mie scattering theory and Monte Carlo (MC) method. Application of backscattered Mueller matrix in property discrimination were investigated first by MC simulation and later validated by corresponding experiments.Mie scattering theory was applied to acquire polarized scattering model, Stokes-Mueller formalism was chose to describe propagation character of polarized light. These two theories were imbedded in standard Wang-Jacques MC model and a calculation algorithm was presented to simulate the polarized light propagation in turbid media. Relationship between backscattered Mueller matrix and scattering, absorption, layered structure, chiral environment and hidden object were discussed in detail, results showed that each parameter has individual effects.Scattering produce a spatial re-distribution of light, while absorption only cause a uniform decrease in intensity. The major contribution to backscattered Mueller matrix comes from ballistic and quasi-ballistic photons. Scattering and absorption were analyzed at first. As scattering enhances the majority of these photons exit from around the centre, result in image intensity increase around the centre and decrease in the edge. For absorption strengthen only intensity weakening was observed. Both can be easily differentiated by Mueller matrix distribution patterns. A two-layer model was also calculated, Mueller matrix represent disparate alterant rule for upper and lower layer, which suggest possibilities for discriminating subtle epidermal structure. Furthermore, a hidden object with different reflection region was studied and dop distribution gave clear distinctness between regions. Finally, the interaction of polarized light and glucose dissolved chiral media were discussed, Mueller matrix present higher optical rotation as glucose augmented. Based on the above investigation, two validate experiments were carried out. Backscattered Mueller matrix of intralipid tissue phantom was measured and different concentration gave different patterns. Dop of backscattered light from three hidden objects in the intralipid phantom were also calculated and contrasts are clear. Both experimental results showed good agreement with simulation conclusions.