Measurement sensitivity and resolution for background oriented schlieren during image recording

Abstract

Background oriented schlieren (BOS) visualization technique is examined by means of optical geometry. Two most important results are the calculation of the sensitivity and spatial resolution of a BOS system, which allows for the determination of the experiment design space. A set of relations that characterize the performance of a BOS measurement is given, with emphasis on the design of background pattern and spatial placement of optical components.

A review of recent developments in schlieren and shadowgraph techniques

“…Raffel [24] notes that conventional cameras (such as consumergrade DSLRs) can also be used for BOS imaging, but should be set for raw or TIFF (uncompressed) image output. Megapixelrange resolution is required to resolve background features, and a telephoto zoom lens is often needed to provide adequate magnification of S, upon which BOS sensitivity depends [60]. BOS also frequently demands high ISO camera sensitivity as well as kWrange floodlight illumination of the background, especially for high-speed imaging and when a lens aperture of f/22 or smaller is needed to maintain both S and B in focus.…”

Background-oriented schlieren (BOS) techniques

“…The dynamic range of the technique for most of the applications is of the order of 50:1, and the measurement error has been found to be in the order of 2-3 % percent of the full scale (Elsinga et al 2004;Hargather and Settles 2012;Vinnichenko et al 2012). Other authors (Popova (2004), Popova et al 2008;Gojani and Obayashi 2012;Gojani et al 2013;Yevtikhiyeva et al 2009) investigated the influence of various parameters on the measurement sensitivity and resolution of BOS analytically and experimentally and presented several guiding formulae for setting up a BOS system. A large number of papers have been published on methods suitable for a general improvement of accuracy and resolution of BOS.…”

The Quantitative Density Measurement of Unsteady Flow around the Projectile

“…The spatial resolution for the observed phenomena will be lower in the case of decreasing F-number, i.e. opening the aperture of the lens, because the cone diameter of the incident light from the background to the camera lens at the observation position becomes larger [12].…”