Nondestructive imaging of shallow buried objects using acoustic computed tomography

Abstract

The nondestructive three-dimensional acoustic tomography concept of the present investigation combines computerized tomography image reconstruction algorithms using acoustic diffracting waves together with depth information to produce a three-dimensional (3D) image of an underground section. The approach illuminates the underground area of interest with acoustic plane waves of frequencies 200-3000 Hz. For each transmitted pulse, the reflected-refracted signals are received by a line array of acoustic sensors located at a diametrically opposite point from the acoustic source line array. For a stratified underground medium and for a given depth, which is represented by a time delay in the received signal, a horizontal tomographic 2D image is reconstructed from the received projections. Integration of the depth dependent sequence of cross-sectional reconstructed images provides a complete three-dimensional overview of the inspected terrain. The method has been tested with an experimental system that consists of a line array of four-acoustic sources, providing plane waves, and a receiving line array of 32-acoustic sensors. The results indicate both the potential and the challenges facing the new methodology. Suggestions are made for improved performance, including an adaptive noise cancellation scheme and a numerical interpolation technique.

A fundamental study for long-distance noncontact shallow underground exploration technology by acoustic irradiation-induced vibration

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An ultrasonic multi-wave focusing and imaging method for linear phased arrays*

“…Nowadays, ultrasonic imaging with phased arrays is an important technology and is widely applied in various fields, including non-destructive testing (NDT), [1][2][3][4] sonar, [5,6] medical diagnosis [7][8][9] and so on. With rapid development of the technology, the industry makes higher requirements for imaging resolution in NDT.…”

Buried Object Detection Method Using Optimum Frequency Range in Extremely Shallow Underground

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