Ultrasonic field mapping using conventional schlieren images

Conventional schlieren is a technique commonly used for visualizing the pressure distribution of a sound field parallel to its direction of propagation. Unfortunately, the phase and amplitude variations of the sound in planes transverse to its direction of propagation are integrated out in this visualization technique. However, an optical method has been proposed by Berlinghieri and Cook [J. Acoust. Soc. Am. 58, 823 (1975)] to extract these sound field characteristics lost in schlieren visualization. In this paper, a computer-based analysis method is established employing a modification of the Berlinghieri and Cook method. The analysis procedure is applied directly to a conventional schlieren image of a 1-MHz transducer. The amplitude and phase (variations) of the sound field of the transducer for a series of transverse planes are extracted from the schlieren image in order to demonstrate a method of ultrasonic field mapping.