Treffer: Pocket schlieren: a background-oriented schlieren imaging platform on a smartphone.

Background-Oriented Schlieren (BOS) is a powerful technique for flow visualization. Nevertheless, the widespread dissemination of BOS is impeded by its dependence on scientific cameras, computing hardware, and dedicated analysis software. In this work, we aim to democratize BOS by providing a smartphone-based, open-access scientific tool called "Pocket Schlieren". Pocket schlieren enables users to directly capture, process, and visualize flow phenomena on their smartphones. The underlying algorithm incorporates consecutive frame subtraction (CFS) and optical flow (OF) techniques to show the density gradients inside a flow. It performs on both engineered and natural background patterns. Using pocket schlieren, we successfully visualized the flow produced from a burning candle flame, butane lighter, hot soldering iron, room heater, water immersion heating rod, and a large outdoor butane flame. We have also demonstrated the flow visualization in liquid medium. It is able to detect minuscule refractive index variations up to the order of ~ 10^–3. Pocket schlieren promises to serve as a frugal yet potent instrument for scientific and educational purposes. [ABSTRACT FROM AUTHOR]

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