中文摘要：

漫反射光谱技术被广泛应用于无创测量生物组织光学性质。当光源与探测器很近时,仅仅依靠吸收系数μ_a和约化散射系数μ′_s不能准确描述光源附近光的传播状态。而二阶光学参量γ的引入改善了近光源光的传播状态的描述。本文将生物组织的散射等效成特定球形颗粒的散射,基于Mie散射理论,计算了与散射相函数p（θ）有关的单粒子和多分散系粒子的二阶光学参量γ,研究了γ随尺度参数α和相对折射率m的变化规律,描述了γ与组织结构参量之间的联系,并阐述了γ对粒子特征的表征能力。研究表明,参量γ对尺度参数α小于2的微粒尺寸的改变是敏感的,并呈二次函数关系,其系数与相对折射率呈线性关系;对于相对折射率和尺度参数都不相同的两个粒子,他们的各向异性因子g相同时,二阶光学参量γ却不同,粒子越大,γ表征粒子特征的能力越强。这对于无创探究组织微观形态具有深远的意义。

英文摘要：

Diffuse reflectance spectroscopy is widely used in non-invasive measurement of tissue optical properties.At small source-detector separations,relying solely on the absorption coefficient μ_a and the reduced scattering coefficient μ′_s can not accurately describe the light propagation state near light source.And the introduction of the second-order optical parameterγimproves the description of light propagation conditions near the source.Based on Mie scattering theory,this paper considers the scattering of tissue as the scattering of specific spherical particles and performs precise calculation of the second-order optical parameterγabout single-particle and polydisperse particle system.And the changes of the second-order optical parameterγwhich is associated with the scattering phase function with size parameterαand relative refractive index mare analyzed.What＇s more,the relation betweenγand tissue structure parameters is reflected and it elaborates the representational capacity of the second-order optical parameterγfor characteristics of particles.The study has shown that there is sensitive variation ofγwith particulate size changing when the size parameterαis less than 2,and there is a quadratic function relationship betweenγandα,the fitting coefficients and relative refractive index presents linear relation.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.This is of great significance for non-invasive exploration of micro-morphology.