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Schlieren imaging is a method to visualize density variations in transparent media.〔 A. Korpel, D. Mehrl and H.H. Lin, ''Schlieren Imaging of Sound Fields'', IEEE 1987 Ultrasonics Symposium, pages: 515–518, (1987). 〕 In particular, the term "Schlieren imaging" refers to the implementation of Schlieren photography to visualize the pressure field produced by ultrasonic 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 HIFU transducers), detection of acoustic beam-profile irregularities (e.g. due to defects in transducer) and on-line identification of time-dependent phenomena 〔 S.A. Brown, et al., ''Characterization of Nonthermal Focused Ultrasound for Noninvasive Selective Fat Cell Disruption (Lysis): Technical and Preclinical Assessment'', Plast. Reconstr. Surg., 124(1), pages: 92–101, (2009). 〕 (e.g. in phased array transducers). Some researchers say that Schlieren imaging is equivalent to an X-ray radiograph of the acoustic field. == Setup == The optical setup of a Schlieren imaging system may comprise the following main sections: 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 used) placed in the focal point of a collimating optical element (lens or mirror). The focusing element may be a lens or a mirror. The optical stop may be realized by a razor placed horizontally or vertically in the focal point of the focusing element, carefully positioned to block the light spot image on its edge. The camera is positioned behind the stop and may be equipped with a suitable lens. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Schlieren imaging」の詳細全文を読む スポンサード リンク
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