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Proceedings Paper

Imaging of acoustic waves in sand
Author(s): Vance A Deason; Ken L Telschow; Scott M Watson
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Paper Abstract

There is considerable interest in detecting objects such as landmines shallowly buried in loose earth or sand. Various techniques involving microwave, acoustic, thermal and magnetic sensors have been used to detect such objects. Acoustic and microwave sensors have shown promise, especially if used together. In most cases, the sensor package is scanned over an area to eventually build up an image or map of anomalies. We are proposing an alternate, acoustic method that directly provides an image of acoustic waves in sand or soil, and their interaction with buried objects. The INEEL Laser Ultrasonic Camera utilizes dynamic holography within photorefractive recording materials. This permits one to image and demodulate acoustic waves on surfaces in real time, without scanning. A video image is produced where intensity is directly and linearly proportional to surface motion. Both specular and diffusely reflecting surfaces can be accommodated and surface motion as small as 0.1 nm can be quantitatively detected. This system was used to directly image acoustic surface waves in sand as well as in solid objects. Waves at frequencies of 16 kHz were generated using modified acoustic speakers. These waves were directed through sand toward partially buried objects. The sand container was not on a vibration isolation table, but sat on the lab floor. Interaction of wavefronts with buried objects showed reflection, diffraction and interference effects that could provide clues to location and characteristics of buried objects. Although results are preliminary, success in this effort suggests that this method could be applied to detection of buried landmines or other near-surface items such as pipes and tanks.

Paper Details

Date Published: 10 November 2003
PDF: 7 pages
Proc. SPIE 5191, Optical Diagnostics for Fluids, Solids, and Combustion II, (10 November 2003); doi: 10.1117/12.504832
Show Author Affiliations
Vance A Deason, Idaho National Engineering and Environmental Lab. (United States)
Ken L Telschow, Idaho National Engineering and Environmental Lab. (United States)
Scott M Watson, Idaho National Engineering and Environmental Lab. (United States)


Published in SPIE Proceedings Vol. 5191:
Optical Diagnostics for Fluids, Solids, and Combustion II
Patrick V. Farrell; Fu-Pen Chiang; Carolyn R. Mercer; Gongxin Shen, Editor(s)

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