Security applications may require the ability to image through electromagnetic shields. This is for
example the case when trafficking of illicit material involves cargo containers. Thus, suitable detection
techniques are required to penetrate a ferromagnetic enclosure. We report on the demonstration of the
ability of a system based on electromagnetic interrogation techniques to create magnetic images of
metallic objects concealed within metallic enclosures. The penetrating power through single and
double ferromagnetic enclosures was investigated. The instrument employs a driver Helmholtz-coil
assembly and an array of 20 × 20 sensor coils. The sample objects were imaged via phase variation
measurements between the driver and sensor coils, due to inductive coupling between the coils and
the sample object
