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Schlieren imaging system setup: linear lens-based configuration. The optical setup of a schlieren imaging system may comprise the following main sections: [citation needed] Parallel beam, focusing element, stop (sharp edge) and a camera. The parallel beam may be achieved by a point-like light source (a laser focused into a pinhole is sometimes ...
Focusing schlieren systems can use compact optics with a large background illumination pattern, which is particularly easy to produce with a projection system. For systems with large demagnification, the illumination pattern needs to be around twice larger than the field of view to allow defocusing of the background pattern.
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).
Here, Mach 4 flow over a pitot probe is observed by schlieren optics in the Penn State Supersonic Wind Tunnel. The flow direction is left-to-right. The flow direction is left-to-right. A supersonic wind tunnel is a wind tunnel that produces supersonic speeds (1.2< M <5) The Mach number and flow are determined by the nozzle geometry.
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.
A major advantage of the technique is that it is less sensitive to mechanical vibration, and it is therefore widely used in the ophthalmic industry for laminar analysis. A similar implementation in wind tunnel application for quantitative measurement is moire schlieren, a variation of schlieren photography. [3]
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.
Afocal photography works with any system that can produce a virtual image of parallel light, for example telescopes and microscopes. Afocal photographic setups work because the imaging device's eyepiece produces collimated light and with the camera's lens focused at infinity, creating an afocal system with no net convergence or divergence in the light path between the two devices. [2]