Modeling considerations for imaging with a standard metal detector

Abstract

A standard pulsed induction metal. detector is used to image buried metallic objects by scanning an area of interest. It is shown that, under specific hypotheses, the output image is the result of the convolution of a target function with a kernel depending on the incident magnetic field. Several hypotheses are considered, leading to different kernel shapes and different interpretations of the target function. As the detector imaging function is a low-pass filter, shape's details spread out and the resulting raw image are blurred, Since a high-pass restoration filter must be used to deconvolve the raw images, care must be taken to avoid a strong amplification of noise. The imaging filter is computed using a numerical simulation of the incident magnetic field. Finally, the restoration filter is computed using the Wiener approach. Results are shown for a couple of metallic pieces.