Prokhorov Alexander V, Mekhontsev Sergey N, Hanssen Leonard M
Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8442, USA.
Appl Opt. 2003 Jul 1;42(19):3832-42. doi: 10.1364/ao.42.003832.
The Monte Carlo method has been applied to numerical modeling of an integrating sphere designed for hemispherical-directional reflectance factor measurements. It is shown that a conventional algorithm of backward ray tracing used for estimation of characteristics of the radiation field at a given point has slow convergence for small source-to-sphere-diameter ratios. A newly developed algorithm that substantially improves the convergence by calculation of direct source-induced irradiation for every point of diffuse reflection of rays traced is described. The method developed is applied to an integrating sphere reflectometer for the visible and infrared spectral ranges. Parametric studies of hemispherical radiance distributions for radiation incident onto the sample center were performed. The deviations of measured sample reflectance from the actual reflectance as a result of various factors were computed. The accuracy of the results, adequacy of the reflectance model, and other important aspects of the algorithm implementation are discussed.
蒙特卡罗方法已应用于为半球方向反射率因子测量设计的积分球的数值建模。结果表明，用于估计给定点辐射场特性的传统反向光线追踪算法，对于小的源与球直径比，收敛速度较慢。描述了一种新开发的算法，该算法通过计算所追踪光线的每一个漫反射点处由源直接引起的辐照度，大幅提高了收敛速度。所开发的方法应用于可见和红外光谱范围的积分球反射仪。对入射到样品中心的辐射的半球辐射亮度分布进行了参数研究。计算了由于各种因素导致的测量样品反射率与实际反射率的偏差。讨论了结果的准确性、反射率模型的适用性以及算法实现的其他重要方面。
