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Proceedings Paper

Ultrasonic displacement sensor for the seismic detection of buried land mines
Author(s): James S. Martin; Douglas J. Fenneman; Fabien T. Codron; Peter H. Rogers; Waymond R. Scott Jr.; Gregg D. Larson; George S. McCall II
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Paper Abstract

A system is under development that uses seismic surface waves to detect and image buried landmines. The system, which has been previously reported in the literature, requires a sensor that does not contact the soil surface. Thus, the seismic signal can be evaluated directly above a candidate mine location. The system can then utilize small amplitude and non-propagating components of the seismic wave field to form an image. Currently, a radar-based sensor is being used in this system. A less expensive alternative to this is an ultrasonic sensor that works on similar principles to the radar but exploits a much slower acoustic wave speed to achieve comparable performance at an operating frequency 5 to 6 decades below the radar frequency. The prototype ultrasonic sensor interrogates the soil with a 50 kHz acoustic signal. This signal is reflected from the soil surface and phase modulated by the surface motion. The displacement can be extracted from this modulation using either analog or digital electronics. The analog scheme appears to offer both the lowest cost and the best performance in initial testing. The sensor has been tested using damp compacted sand as a soil surrogate and has demonstrated a spatial resolution and signal-to-noise ratio comparable to those that have been achieved with the radar sensor. In addition to being low-cost, the ultrasonic sensor also offers the potential advantage of penetrating different forms of ground cover than those that are permeable to the radar signal. This is because density and stiffness contrasts mediate ultrasonic reflections whereas electromagnetic reflection is governed by dielectric contrast.

Paper Details

Date Published: 13 August 2002
PDF: 11 pages
Proc. SPIE 4742, Detection and Remediation Technologies for Mines and Minelike Targets VII, (13 August 2002); doi: 10.1117/12.479132
Show Author Affiliations
James S. Martin, Georgia Institute of Technology (United States)
Douglas J. Fenneman, Georgia Institute of Technology (United States)
Fabien T. Codron, Georgia Institute of Technology (United States)
Peter H. Rogers, Georgia Institute of Technology (United States)
Waymond R. Scott Jr., Georgia Institute of Technology (United States)
Gregg D. Larson, Georgia Institute of Technology (United States)
George S. McCall II, Georgia Tech Research Institute (United States)

Published in SPIE Proceedings Vol. 4742:
Detection and Remediation Technologies for Mines and Minelike Targets VII
J. Thomas Broach; Russell S Harmon; Gerald J. Dobeck, Editor(s)

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