中文摘要：

研究了一个改进的漫射近似模型.该模型将漫射近似中的漫射系数D用描述P3近似的漫射系数Dasym替代.推导了这个混合的漫射近似模型在单点源近似和外推边界条件下的反射率RHybrid（ρ）的解析表达式,比较了有效反照率a′对标准漫射近似RDA（ρ）和RHybrid（ρ）的影响;用RHybrid（ρ）反演光学参量并求其误差,对其适用范围进行了分析.研究结果表明,与漫射近似RDA（ρ）仅适用于强散射和远离光源的情况相比,改进后的混合漫射近似模型RHybrid（ρ）能够应用于吸收系数较大的散射介质,并能较好地描述光源附近的辐射强度分布.

英文摘要：

A modified diffusion approximation is investigated.In this theoretical model,diffusion coefficient D of the standard diffusion approximation is substituted by diffusion coefficient D_ asym of P_3 approximation.Analytic solution R_ Hybrid（ρ） of this hybrid diffusion for reflectance in single source approximation and steady-state case with extrapolated boundary is obtained,influences of the transport albedo a＇ on the standard diffusion approximation R_ DA（ρ） and the hybrid diffusion approximation R_ Hybrid（ρ） are compared,recovering of optical parameters from diffuse reflectance R_ Hybrid（ρ） is demonstrated,and the errors and application ranges are studied.The results show that this hybrid diffusion approximation R_ Hybrid（ρ） can be used in strong absorption media and at short source-detector separation.