schlieren imaging
Schlieren imaging is a method to visualize density variations in transparent media;[1]
Schlieren imaging of a focusing ultrasonic transducer
in particular, the term "Schlieren imaging" refers to the implementation of schlieren photography (also: Schlieren) to visualize the pressure field produced byultrasonic transducer, generally in water or in other tissue-mimicking media. The method provides a two-dimensional (2D) projection image of the acoustic beam in real-time ("Live Video"). The unique properties of the method enable the investigation of specific features of the acoustic field (e.g. focal point in HIFUtransducers), detection of acoustic beam-profile irregularities (e.g. due to defects in transducer) and on-line identification of time-dependent phenomena [2] (e.g. inphased array transducers). Some researchers say that Schlieren imaging is equivalent to an X-ray radiograph of the acoustic field.