Shendeleva Margarita L, Molloy John A
Photonic Processes Department, Institute of Physics, Kiev, Ukraine.
J Opt Soc Am A Opt Image Sci Vis. 2007 Sep;24(9):2902-10. doi: 10.1364/josaa.24.002902.
A spatially varying refractive index leads to the bending of photon paths in a medium, which complicates the Monte Carlo modeling of a photon random walk. We show that the process of photon diffusion in a turbid medium with varying refractive index and curved photon paths can be mapped to the diffusion process in a medium with straight photon paths and modified optical properties. Specifically, the diffusion coefficient, the absorption, and the refractive index of the second medium should differ from the corresponding properties of the first medium by the factor of the squared refractive index of the first medium. The specific intensity of light in the second medium will then be equal to the specific intensity in the first medium divided by the same factor, which also means that the photon density distributions in the two media will be identical. In a Monte Carlo simulation the scaling property suggests that two different algorithms can be used to obtain the photon density distribution, namely, the algorithm with curved photon paths and given optical properties and the algorithm with straight photon paths and modified optical properties.
空间变化的折射率会导致光子路径在介质中发生弯曲，这使得光子随机游走的蒙特卡罗建模变得复杂。我们表明，在具有变化折射率和弯曲光子路径的混浊介质中，光子扩散过程可以映射到具有直光子路径和修改光学性质的介质中的扩散过程。具体而言，第二介质的扩散系数、吸收率和折射率应与第一介质的相应性质相差第一介质折射率平方的倍数。然后，第二介质中的光比强度将等于第一介质中的比强度除以相同倍数，这也意味着两种介质中的光子密度分布将是相同的。在蒙特卡罗模拟中，这种缩放特性表明可以使用两种不同的算法来获得光子密度分布，即具有弯曲光子路径和给定光学性质的算法以及具有直光子路径和修改光学性质的算法。
