Quantitative Schlieren imaging based on fringe projection

Psota, Pavel; Stašík, Marek; Kredba, Jan; Lédl, Vít; Jašíková, Darina; Kotek, Michal; Kopecký, Václav

doi:10.1051/epjconf/202226401034

Cited by 2 publications

(4 citation statements)

References 6 publications

(6 reference statements)

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“…The FOV of the proof-of-concept system is currently set to 26 26 mm , restricted by the telecentric lens. Note, however, that schlieren based on intensity-modulation can be used to visualize larger objects 34 , as demonstrated in Fig. S4, where the FOV is 110 110 mm and Supplementary video 2 and 3 .…”

Section: Methodsmentioning

confidence: 99%

“…In this paper we present, to the best of our knowledge, the first demonstration of illumination-based schlieren videography, where the frame rate is governed by the pulse duration of the light source alone. The presented approach is based on an intensity modulation-scheme, which is a versatile optical method that is used for several different imaging applications, such as topography 31 , super-resolution microscopy 32 , schlieren 19,20,33,34 , interferometry 35,36 and thermometry 37 . Here we combine its ability to provide schlieren images through phasesensitive analysis 20 with its ability to optically multiplex temporally separated image data 28,[38][39][40] into a powerful imaging concept.…”

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confidence: 99%

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High-speed videography of transparent media using illumination-based multiplexed schlieren

Kornienko

Roth

et al. 2022

Sci Rep

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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.

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

High-speed videography of transparent media using illumination-based multiplexed schlieren

Kornienko

Roth

et al. 2022

Sci Rep

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“…Generally, a random dot pattern becomes a background pattern in BOS imaging [1,2]. However, implementing BOS imaging is also recently considering an application with periodic pattern types as the background [13,14].…”

Section: Introductionmentioning

confidence: 99%

“…However, all literature uses the random dot as the background and the digital image correlation (DIC) as the image processing algorithm without including uncertainty evaluation. Using a random dot in BOS imaging introduces an inhomogeneous distribution in the background plane [13,14], and the dot can experience a shape distortion due to large density gradients [17]. In addition, the DIC algorithm also has drawbacks, for example, assuming that the displacement image is approximately constant.…”

Section: Introductionmentioning

confidence: 99%

Calibration of a background-oriented schlieren (BOS) imaging based on the light deflection angle of a wedge prism

Sasono,

Sakti,

Noor

et al. 2024

Metrology and Measurement Systems

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The background oriented schlieren (BOS) imaging relies on measuring the light deflection angle in proportion to the refractive index gradient due to the change in the density of a medium. BOS imaging is sensitive to light deflection, and the quantitative measurement requires a reliable calibration method. It is convenient to calibrate the BOS based on the measurement of light deflection. All current BOS calibrations use the random dot as the background and digital image correlation (DIC) as the processing algorithm. Such calibrations can induce an inaccurate measurement. This paper proposes a new method to calibrate the BOS based on measuring a known light deflection angle of a wedge prism. The proposed method uses a fringe pattern instead of the random-dot and works based on phase demodulation. The fringe patterns are phase modulated by the wedge prism (the schlieren object). The demodulation utilizes the Hilbert transform (HT) on the BOS images, giving the phase difference of the images. The BOS converts the phase difference into the deflection angle. The calibration relies on the deviation of the angle measured by the BOS with the known angle of a wedge prism. The results show that the measurement accuracy of the BOS can achieve more than 95%. This result shows high accuracy in measuring the light deflection angle. Also, the proposed method is more accurate than other methods, and fringe patterns outperform random dot patterns in BOS imaging. Soon, this proposed calibration method can be adopted to validate the instruments for measuring the physical properties of a transparent medium in two-dimensional (2-D) visualization, in a contactless and non-intrusive manner.

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Quantitative Schlieren imaging based on fringe projection

Cited by 2 publications

References 6 publications

High-speed videography of transparent media using illumination-based multiplexed schlieren

High-speed videography of transparent media using illumination-based multiplexed schlieren

Calibration of a background-oriented schlieren (BOS) imaging based on the light deflection angle of a wedge prism

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