Metal object detecting apparatus
First Claim
1. A metal object detecting apparatus comprising,(i) a transmitter for generating a time varying primary magnetic field within a surveillance volume, the magnetic field having a non-zero magnitude throughout substantially all of the surveillance volume and a resultant magnetic field direction which varies along any substantially linear path through the surveillance volume such that at three locations along said path the resultant magnetic field points in three mutually substantially orthogonal directions,(ii) a detector for measuring a secondary magnetic field at a plurality of positions as a function of time due to the presence of a metal object within the surveillance volume as it passes a plurality of measurement points there-through, the detector being arranged to substantially reject the primary magnetic field, and(iii) a processor for determining from the measured secondary magnetic fields a track through the surveillance volume comprising a plurality of locations of the metal object within the surveillance volume and a magnetic moment thereof at each location, the processor being adapted in use to derive there-from a magnetic signature that is characteristic of the metal object and independent of the orientation and track of the metal object through the surveillance volume.
2 Assignments
0 Petitions
Accused Products
Abstract
A metal object detecting apparatus comprising, a transmitter for generating a primary magnetic field having a resultant magnetic field direction which varies along any substantially linear path through a surveillance volume such that at three locations along said path the resultant magnetic field points in three mutually substantially orthogonal directions; a detector for measuring a secondary magnetic field at a plurality of positions as a function of time due to the presence of a metal object within the surveillance volume as it passes a plurality of measurement points there-through; and a processor for determining from the measured secondary magnetic fields a track through the surveillance volume comprising a plurality of locations of the metal object and a magnetic moment thereof at each location, the processor being adapted in use to derive there-from a magnetic signature that is characteristic of the metal object and independent of the orientation and track of the metal object.
31 Citations
50 Claims
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1. A metal object detecting apparatus comprising,
(i) a transmitter for generating a time varying primary magnetic field within a surveillance volume, the magnetic field having a non-zero magnitude throughout substantially all of the surveillance volume and a resultant magnetic field direction which varies along any substantially linear path through the surveillance volume such that at three locations along said path the resultant magnetic field points in three mutually substantially orthogonal directions, (ii) a detector for measuring a secondary magnetic field at a plurality of positions as a function of time due to the presence of a metal object within the surveillance volume as it passes a plurality of measurement points there-through, the detector being arranged to substantially reject the primary magnetic field, and (iii) a processor for determining from the measured secondary magnetic fields a track through the surveillance volume comprising a plurality of locations of the metal object within the surveillance volume and a magnetic moment thereof at each location, the processor being adapted in use to derive there-from a magnetic signature that is characteristic of the metal object and independent of the orientation and track of the metal object through the surveillance volume.
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33. A method of detecting a metal object within a surveillance volume comprising the steps of:
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(i) generating a time varying primary magnetic field within the surveillance volume, the magnetic field being arranged to have a non-zero magnitude throughout substantially all of the surveillance volume and a resultant magnetic field direction which varies along any substantially linear path through the surveillance volume such that at three locations along said path the resultant magnetic field points in three mutually substantially orthogonal directions, (ii) measuring a secondary magnetic field at a plurality of positions as a function of time due to the presence of a metal object within the surveillance volume as it passes a plurality of measurement points there-through, (iii) determining from the measured secondary magnetic fields a track through the surveillance volume comprising a plurality of locations of the metal object within the surveillance volume and a magnetic moment thereof at each location, (iv) deriving from the plurality of locations of the metal object within the surveillance volume and the magnetic moment thereof at each location a magnetic signature that is characteristic of the metal object and independent of the orientation and track of the metal object through the surveillance volume. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50)
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Specification