Shuaib Ali, Yao Gang
Department of Biological Engineering, University of Missouri, Columbia, Missouri 65211, USA.
Appl Opt. 2010 Feb 10;49(5):838-44. doi: 10.1364/AO.49.000838.
Light propagation in a fibrous anisotropic scattering medium is quite different from that in an isotropic medium. Both the anisotropic diffuse equation (ADE) and the continuous time random walk (CTRW) theory predict that the equi-intensity profiles of the surface reflectance have an elliptical shape in a fibrous turbid medium. In this study, we simulated the spatially resolved surface reflectance in a fibrous sample using a Monte Carlo model. A parametric equation was used to quantitatively characterize the geometric profiles of the reflectance patterns. The results indicated that the equi-intensity profiles of surface reflectance had elliptical shapes only when evaluated at distances far away from the incident point. The length ratio of the two orthogonal axes of the ellipse was not affected by the sample optical properties when the ratio of reduced scattering coefficients along the two axes is the same. But the relationship between the aforementioned two ratios was different from the predication of ADE theory. Only for fibers of small sizes did the fitted axes ratios approach the values predicted from the ADE theory.
光在纤维状各向异性散射介质中的传播与在各向同性介质中的传播有很大不同。各向异性扩散方程（ADE）和连续时间随机游走（CTRW）理论均预测，在纤维状混浊介质中，表面反射率的等强度轮廓呈椭圆形。在本研究中，我们使用蒙特卡罗模型模拟了纤维状样品中的空间分辨表面反射率。使用参数方程定量表征反射图案的几何轮廓。结果表明，仅在远离入射点的距离处评估时，表面反射率的等强度轮廓才呈椭圆形。当沿两个轴的约化散射系数之比相同时，椭圆两个正交轴的长度比不受样品光学性质的影响。但上述两个比率之间的关系与ADE理论的预测不同。仅对于小尺寸的纤维，拟合的轴比才接近ADE理论预测的值。
