METHOD AND APPARATUS FOR DETECTING AND CLASSIFYING METALLIC OBJECTS

摘要

A method and apparatus for detecting and classifying metallic objects, the apparatus (100) including a transmitter having a transmit coil (102) for transmitting a magnetic field in response to a driving electrical signal, and a receiver having a detector coil (104) for generating a detected electrical signal in response to changes in magnetic fields. The method detects metallic objects within a target volume of the apparatus, and includes driving the transmitter coil with a piecewise linear current waveform (400) having at least two linear segments (402, 404). The method further includes measuring a detected signal waveform (708) at the detector coil, and analysing the detected waveform to identify features characteristic of the presence of metallic objects within said target volume. The apparatus includes a driver (120, 122, 124, 126) configured to drive the transmit coil (102) with a piecewise linear waveform (400), and an analyser configured to analyse the corresponding detected signal waveform. The method and apparatus substantially mitigates problems associated with the transmission of non linear magnetic fields commonly associated with known metal detection apparatus and methods.