Detection and Classification of Buried Metallic Objects

摘要

A prototype active electromagnetic system has been developed for detecting and characterizing UXO. The system employs three orthogonal loop transmitters and eight vertical field detectors deployed in the plane of the horizontal loop transmitter. The location and orientation of the three principal polarizabilities of a target can be recovered from a single position of the transmitter-receiver system. Further characterization of the target is obtained from the broadband response. The system employs a bipolar half sine pulse train current waveform and the detectors are dB/dt induction coils designed to minimize the transient response of the primary field pulse. The target transient is recovered in a 40(dot)s to 1.0 ms window. The ground response imposes an early time limit on the time window and system/ambient noise limits the late time response. Nevertheless for practical transmitter moments and optimum receivers the size the size and the ratio of conductivity to permeability can be accurately recovered. The prototype system has successfully recovered the depths and polarizabilities of ellipsoidal test targets.