Study Of Scattering-phase-function-dependent Parameter ? Of Turbid Media

The scattering signal of light carries the information on the morphology and structure of the particles,so the scattering parameters can be used to describe the fine changes in the particles and the structural differences of the biological tissue.The scattering phase function(SPF)describes the light scattering angle distribution of a single particle,which is related to the morphology and sub-microstructure of the biological tissue.Therefore,it is necessary to study the optical parameters related to the phase function.Currently widely used anisotropy factor g is SPF-dependent parameter,but g is usually implicit in the reduced scattering coefficient ?'s.When the separation distance between the light source and the detector is short,the light distribution near the light source can not be accurately described by the absorption coefficient ?a,and the reduced scattering coefficient ?'s,but the introduction of the optical parameter y related to the scattering phase function can improves the description of the light distribution.Based on Mie scattering theory,the scattering of biological tissue is considered as the scattering of specific spherical particles and this paper performs precise calculation of the anisotropy factor g and second-order optical parameter y about single-particle and polydisperse particle system.The changes of the parameter y with size parameter a and relative refractive index m are analyzed,the representational capacity of the parameter ? for characteristics of particles is demonstrated.The study has shown that the ? changes with particulate size a is sensitive when the a is less than 2,and a quadratic function relationship between? and ? is appeared.For two particles having different relative refractive indexs and size parameters,the two second order optical parameters are different when their anisotropy factors are the same.And the larger the particle is,the stronger the ability of characterizing the particle is,which is indicated in this paper.Based on the Mie scattering theory,the second-order optical parameters y of the particles with the diameter of the logarithmic normal distribution are calculated and analyzed.The parameters ? are related not only to the mean radius of the polydisperse particle system but also to the shape parameter ?.Using Mie scattering theory,the fractal model of biological tissue is studied.The anisotropy factor g and the second order optical parameters ? under different conditions are programmed by Matlab,and the physical meaning of the parameter ? is expounded in detail.In the paper,Monte Carlo simulation is used to investigate the light propagation in biological tissues.In the Monte Carlo program,the scattering probability distribution of the photon is described by the Mie scattering phase function.An optical model which is applicable to weak absorption and related to the second-order optical parameters y is established.On the basis of the model,the parameter y is obtained according to the reflectivity.