Importance sampling is a Monte Carlo technique in which rays are generated and propagated in specific directions in the optical system, which are “important” in determining the results you need. This improves sampling by increasing the number of rays reaching the surface or surfaces of interest to the user. Importance sampling is essential in a stray light analysis, where the attenuation of incident light can be very great, and can be helpful in other types of analyses. In a stray light analysis, there should be an importance sampling target for each optical surface in the optical system. It is important to remember that importance sampling is used only to enhance the sampling of scattered and diffracted light or surface sources. Designs that include only specular reflection and transmission cannot take advantage of importance sampling — the direction of the rays is determined by the Law of Reflection and Snell’s Law.
Figure 7.1 on page 7.3 illustrates importance sampling for the simple case of a lens that scatters from its second surface. A second object is shown that corresponds to a detector. In this case rays from an off-axis field position are imaged such that all of the specular rays miss the detector. Generally, scattering is stronger close to the specular direction of the un-scattered ray so the probability of a randomly scattered ray hitting the detector is very small. When an importance target is applied, it guarantees that the one or more importance rays will hit the detector for each incident ray.
| lok619 | 2018-02-02 12:25 |
bulk scattering,。谢谢关注和帮忙！ 我的模型是这样：几个分布锥环内侧的点光源发光，进入添加有散光粉的锥环后，计算在环顶的光强分布时怎样。图1是一个点光源的实例。图2表示在环内侧上面加个完全受的板挡掉多余的光。现在不知道如何在这个锥环进行体散射的重点采样。 [attachment=81887] [attachment=81888] |
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