Croccolo Fabrizio, Brogioli Doriano
Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, 20133 Milano, Italy.
Appl Opt. 2011 Jul 10;50(20):3419-27. doi: 10.1364/AO.50.003419.
In a schlieren setup, a lens system forms an image of the refractive index fluctuations of a transparent sample onto a matrix detector while an intensity mask is positioned in the Fourier plane of a collecting lens to perform the required spatial filtering. In the absence of the mask, the resulting technique is that of a shadowgraph. The two methods provide different information about the refractive index of transparent fluids and can be used both for visualization purposes and scattering measurements. Here, we describe the effect of the intensity mask on the technique transfer function, i.e., its ability to detect different spatial frequencies and show how the special cases of shadowgraph, schlieren, and the transition between the two can be derived. We also present experimental data that agree well with our predictions.
在纹影系统中，一个透镜系统将透明样品的折射率波动图像形成在矩阵探测器上，同时一个强度掩膜放置在收集透镜的傅里叶平面中以进行所需的空间滤波。在没有掩膜的情况下，所得技术就是阴影图技术。这两种方法提供了关于透明流体折射率的不同信息，并且可用于可视化目的和散射测量。在这里，我们描述了强度掩膜对技术传递函数的影响，即其检测不同空间频率的能力，并展示了如何推导阴影图、纹影的特殊情况以及两者之间的过渡情况。我们还展示了与我们的预测非常吻合的实验数据。
