中文摘要：

推导了扩散近似方程，通过半无限大均匀介质计算，用扩散理论分析解验证了数值方法的有效性。模拟了光在非均匀介质内的传输过程，给出了介质内光通量随时间变化的空间分布。结果表明，该基于扩散模型的数值方法能够模拟短脉冲光在强散射介质中的传播过程以及漫散射光的时间变化特性，并且借助于光通量空间分布能够准确模拟非均匀介质内内含物的位置。

英文摘要：

The diffusion approximation equation has been derived. With a semi-infinite medium, the validity of numerical method is verified compared with analytical approach of the diffusion ap- proximation theory. The propagation of short pulse laser in a two-dimensional nonuniform medium is simulated based on the diffusion approximation equation, and the spatial distribution of fluence in the medium changing with time is presented. The results indicate that the numerical method of diffusion equation in this article can simulate the propagation of short-pulse laser in the scattering medium, and the temporal characteristics of diffusion scattering fluences are illustrated. The heterogeneities can be localized in the background medium with a spatial distribution of fluence.