Precision metal locating apparatus

Claim 2

Apparatus for detecting a metal object having a shape, an electro-magnetic cross-section and a location comprising; transmitter means for generating a time varying magnetic field in the vicinity of the metal object to be detected, thereby inducing currents within the metal object, the induced currents generating a secondary magnetic field, detection means for measuring at least three magnetic field gradient components of at least first order of the secondary magnetic field, processing means for determining at least one of the location, the electro-magnetic cross-section, and an estimate of the shape of the metal object from the measured first order magnetic field gradient components, and adaptive signal processing means for adaptively correcting offsets in the measured magnetic field gradient components.

Claim 3

The apparatus of claim 1 , comprising means for generating a pulsed magnetic field.

Claim 4

The apparatus of claim 1 , comprising means for generating an alternating magnetic field.

Claim 5

The apparatus of claim 1 comprising means for measuring at least five magnetic field gradient components of at least first order, and further comprising sensing means for measuring one or more component of the secondary magnetic field.

Claim 6

The apparatus of claim 4 , wherein the sensing means comprise any one of a coil, a SQUID, a fluxgate, a Hall probe, a magneto-resistive device or a magneto-impedance device.

Claim 7

The apparatus of claim 1 , wherein the processing means includes a least squares fit to one or more classic dipole sources.

Claim 8

The apparatus of claim 1 , wherein the processing means includes a least squares fit to a multi-pole magnetic source.

Claim 9

The apparatus of claim 1 , wherein the processing means includes a least squares fit to extended source models.

Claim 10

The apparatus of claim 1 comprising means for measuring at least three magnetic field gradient components of second order.

Claim 11

The apparatus of claim 1 , comprising at least three pairs of gradiometric receiver coils, each pair for detecting a different first order magnetic field gradient component, each of the gradiometric coil pairs having a baseline, d.

Claim 12

The apparatus of claim 1 , comprising at least three pairs of any one of SQUIDs, fluxgates, Hall probes, magneto-resistive devices or magneto-impedance devices, each pair for detecting a different first order magnetic field gradient component, each of the pairs having a baseline, d.

Claim 13

The apparatus of claim 10 for locating a metal object buried beneath the surface of the earth.

Claim 14

The apparatus of claim 10 for characterising or deducing an estimate of the shape and composition of a metal object buried beneath the surface of the earth.

Claim 15

The apparatus of claim 10 for locating a metal object on or within a human or animal body.

Claim 16

The apparatus of claim 10 for characterising or deducing an estimate of the shape and composition of a metal object on or within a human or animal body.

Claim 17

The apparatus of claim 10 for locating a metal object inside or behind a wall, floor or ceiling.

Claim 18

The apparatus of claim 10 for characterising or deducing an estimate of the shape and composition of a metal object inside or behind a wall, floor or ceiling.

Claim 19

The apparatus of claim 14 , and further comprising a host system, the host system being any one of an ultra-sound scanning apparatus or an X-ray imaging apparatus.

Claim 20

The apparatus of claim 1 , wherein the transmitter means comprise a pulsed current source or an alternating current source and further comprising at least one transmitter coil.

Claim 21

The apparatus of claim 19 , comprising at least two transmitter coils, wherein the two or more transmitter coils are arranged to generate a magnetic field in substantially orthogonal directions.

Claim 22

The apparatus of claim 19 , the transmitter being arranged to generate a magnetic field at at least two frequencies.

Claim 23

The apparatus of claim 1 , wherein the processing means include means for entering pre-determined criteria to provide a discrimination means against detection of metal objects of no interest.

Claim 24

The apparatus of claim 1 , wherein the processing means include means for entering pre-determined criteria to provide a discrimination means to selectively detect metal objects of interest.

Claim 25

The apparatus of claim 1 , the detection means generating at least three outputs corresponding to the three or more measured magnetic field gradient components, and further comprising phase detection means for determining the relative phase between the three or more gradient outputs and the magnetic field generated by the transmitter means, such that the relative phase provides a discrimination means or an additional discrimination means between metal objects of different type.

Claim 26

A detection system suitable for detecting a metal object on or within the human or animal body comprising a host instrument incorporating a plurality of sensor means wherein at least one of the sensor means includes an apparatus for detecting said metal object, said metal object having a shape, an electro-magnetic cross-section and a location, said apparatus comprising; transmitter means for generating a time varying magnetic field in the vicinity of the metal object to be detected, thereby inducing currents within the metal object, the induced currents generating a secondary magnetic field, detection means, located within said time varying magnetic field, for detecting the secondary magnetic field, comprising at least three pairs of any one of gradiometric receiver coils, SQUIDS, fluxgates, Hall probes, magneto-resistive devices and magneto-impedance devices, each of said three pairs for measuring a different magnetic field gradient component of at least first order of the secondary magnetic field, each of the pairs having a baseline, d, processing means for determining at least one of the location or the electro-magnetic cross-section or an estimate of the shape of the metal object from the measured at least first order magnetic field gradient components, wherein data from the apparatus for detecting the metal object is integrated with data from another of said plurality of sensor means incorporated in the host instrument, and adaptive signal processing means for adaptively correcting offsets in the measured magnetic field gradient components.

Claim 27

A detection system suitable for detecting a metal object on or within the human or animal body comprising a host instrument incorporating a plurality of sensor means wherein at least one of the sensor means includes an apparatus for detecting said metal object, said metal object having a shape, an electro-magnetic cross-section and a location, said apparatus comprising; transmitter means for generating a time varying magnetic field in the vicinity of the metal object to be detected, thereby inducing currents within the metal object, the induced currents generating a secondary magnetic field, detection means, located within said time varying magnetic field, for detecting the secondary magnetic field, comprising at least three pairs of any one of gradiometric receiver coils, SQUIDS, fluxgates, Hall probes, magneto-resistive devices and magneto-impedance devices, each of said three pairs for measuring a different magnetic field gradient component of at least first order of the secondary magnetic field, each of the pairs having a baseline, d, processing means for determining at least one of the location or the electro-magnetic cross-section or an estimate of the shape of the metal object from the measured at least first order magnetic field gradient components, wherein data from the apparatus for detecting the metal object is integrated with data from another of said plurality of sensor means incorporated in the host instrument, and adaptive signal processing means for adaptively correcting offsets in the measured magnetic field gradient components.

Claim 28

A system according to claim 25 wherein the sensor means incorporated in the host instrument include any one of an ultra-sound scanning apparatus or an X-ray imaging apparatus.

Claim 31

The method of claim 27 , and further comprising the step of applying within the processing means at least squares fit to one or more classic dipole sources.

Claim 32

The method of claim 27 , and further comprising the step of applying within the processing means a least squares fit to a multi-pole magnetic source.

Claim 33

The method of claim 27 , and further comprising the step of applying within the processing means a least squares fit to extended source models.

Claim 34

The method of claim 27 , and further comprising the step of entering pre-determined criteria to the processing means to provide a discrimination means against detection of metal objects of no interest.

Claim 35

The method of claim 27 , and further comprising the step of entering pre-determined criteria to the processing means to provide a discrimination means to selectively detect metal objects of interest.

Claim 38

A method according to claim 33 wherein the at least one additional sensor means includes any one of an ultrasound scanning apparatus or an X-ray imaging apparatus.