Application of tomographic techniques to Schlieren imaging

纹影成像和摄影作为跨音速流动的流动可视化技术已经使用了近150年，当时August Toepler发现他可以通过使平行光束穿过感兴趣的区域来观察空气密度的变化。如果在成像透镜的焦点处使用刀口，则由折射率的变化引起的偏转表现为亮图案和暗图案。然而，在这段时间的大部分时间里，它更多地用于定性而不是定量测量。这个图像是所有流动现象的二维视图，就像X射线显示整个身体一样。

Schlieren imaging and photography have been used as a flow visualization technique in transonic flows for almost 150 years when August Toepler discovered that he could see variations in air density by shining parallel beams of light through the region of interest. The deflection caused by the variation of the indices of refraction appear as light and dark patterns if a knife-edge is used at the focal point of the imaging lens. However during most of this time, it has since been used more for qualitative rather than quantitative measurements. This image is a 2 dimensional view of the all the flow phenomena much like an X-ray shows all of the body.