Ek Simon, Kornienko Vassily, Roth Adrian, Berrocal Edouard, Kristensson Elias
Division of Combustion Physics, Lund University, Professorsgatan 1, Lund, Sweden.
Sci Rep. 2022 Nov 8;12(1):19018. doi: 10.1038/s41598-022-23198-6.
Schlieren photography is widely used for visualizing phenomena within transparent media. The technique, which comes in a variety of configurations, is based on detecting or extracting the degree to which light is deflected whilst propagating through a sample. To date, high-speed schlieren videography can only be achieved using high-speed cameras, thus limiting the frame rate of such configurations to the capabilities of the camera. Here we demonstrate, for the first time, optically multiplexed schlieren videography, a concept that allows such hardware limitations to be bypassed, opening up for, in principle, an unlimited frame rate. By illuminating the sample with a rapid burst of uniquely spatially modulated light pulses, a temporally resolved sequence can be captured in a single photograph. The refractive index variations are thereafter measured by quantifying the local phase shift of the superimposed intensity modulations. The presented results demonstrate the ability to acquire a series of images of flame structures at frame rates up to 1 Mfps using a standard 50 fps sCMOS camera.
纹影摄影术被广泛用于可视化透明介质中的现象。该技术有多种配置，其原理是检测或提取光在穿过样品时的偏转程度。迄今为止，高速纹影摄像只能通过高速相机实现，因此此类配置的帧率受限于相机的性能。在此，我们首次展示了光学复用纹影摄像技术，这一概念能够绕过此类硬件限制，原则上实现无限帧率。通过用快速爆发的独特空间调制光脉冲照射样品，可以在一张照片中捕获时间分辨序列。此后，通过量化叠加强度调制的局部相移来测量折射率变化。所呈现的结果表明，使用标准的50帧每秒的科学互补金属氧化物半导体（sCMOS）相机，能够以高达100万帧每秒的帧率获取一系列火焰结构图像。
