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The term "schlieren imaging" is commonly used as a synonym for schlieren photography, though this article particularly treats visualization of the pressure field produced by ultrasonic transducers, generally in water or tissue-mimicking media. The method provides a two-dimensional (2D) projection image of the acoustic beam in real-time ("live ...
Background-oriented schlieren technique (BOS [7]) relies on measuring or visualizing shifts in focused images. In these techniques, the background and the schlieren object (the distortion to be visualized) are both in focus and the distortion is detected because it moves part of the background image relative to its original position.
Toepler's original system [2] was designed to detect schlieren in glass used to make lenses. In the conventional schlieren system, [3] a point source is used to illuminate the test section containing the schliere. An image of this light is formed using a converging lens (also called a schlieren lens).
The early days of PIV can be credited to the pioneering work of Ludwig Prandtl, a German physicist and engineer, who is often regarded as the father of modern aerodynamics. In the 1920s, Prandtl and his colleagues used shadowgraph and schlieren techniques to visualize and measure flow patterns in wind tunnels.
Synthetic schlieren is a process that is used to visualize the flow of a fluid of variable refractive index. Named after the schlieren method of visualization, it consists of a digital camera or video camera pointing at the flow in question, with an illuminated target pattern behind. The method was first proposed in 1999.
Acousto-optics is a branch of physics that studies the interactions between sound waves and light waves, especially the diffraction of laser light by ultrasound (or sound in general) through an ultrasonic grating. A diffraction image showing the acousto-optic effect.
It is related to, but simpler than, the schlieren and schlieren photography methods that perform a similar function. Shadowgraph is a type of flow visualisation. In principle, a difference in temperature, a different gas, or a shock wave in the transparent air cannot be seen by the human eye or cameras.
Laser schlieren deflectometry (LSD) is a method for a high-speed measurement of the gas temperature in microscopic dimensions, in particular for temperature peaks under dynamic conditions at atmospheric pressure.