Abstract: A security screening installation system for use in a controlled environment is described. In an embodiment, a passive detector apparatus does not produce a magnetic field for detection and relies on detecting changes in the local magnetic field. The apparatus is: (i) battery powered; (ii) light enough to be hand carried by hand and set up by one person; (iii) comprises a single elongate housing; and (iv) operable between a packed state inside a protective case and a ready to use state outside of the protective case. The housing supports at least two magnetic sensors that define a gradiometer which is arranged to produce a signal indicative of an ambient magnetic field or gradient over a zone of sensitivity which extends away from the housing, wherein a size of the zone is large enough to contain a whole body of a person.

Abstract: A method of detecting contraband about a person using a portable detector apparatus having an elongate housing that supports at least one magnetic sensor, which is arranged to produce a signal indicative of an ambient magnetic field or gradient over a zone of sensitivity which extends away from the housing, the size of the zone large enough to contain the whole body of the person, and a signal processing circuit that receives as an input the signal from the magnetic sensor and which, in response to a change in the signal, produces an alert signal includes setting up the portable detector apparatus in a chosen location, causing the person to pass alongside the housing from outside of the zone of sensitivity into the zone of sensitivity, and monitoring for the issue of an alert by the device which is indicative of the possible presence of contraband.

Abstract: A method of detecting contraband about a person using a portable detector apparatus having an elongate housing that supports at least one magnetic sensor, which is arranged to produce a signal indicative of an ambient magnetic field or gradient over a zone of sensitivity which extends away from the housing, the size of the zone large enough to contain the whole body of the person, and a signal processing circuit that receives as an input the signal from the magnetic sensor and which, in response to a change in the signal, produces an alert signal includes setting up the portable detector apparatus in a chosen location, causing the person to pass alongside the housing from outside of the zone of sensitivity into the zone of sensitivity, and monitoring for the issue of an alert by the device which is indicative of the possible presence of contraband.

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.

Abstract: A metal detection apparatus includes a transmitter for generating a magnetic field in the vicinity of the metal object, and a detector for detecting a secondary magnetic field. The detector include a first gradiometer for providing a first output signal representative of a first direction, y, to the metal object, a second gradiometer arranged substantially orthogonal to the first gradiometer for providing a second output signal representative of a second direction, x, to the metal object, the second direction being substantially orthogonal to the first direction and in the same plane as the first direction, and an outer coil and an inner coil arranged to be substantially concentric with one another and each of which is arranged to provide an output signal representative of secondary magnetic field strength in a third direction, z, which is substantially orthogonal to the plane of the first and second directions.

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.

Abstract: Apparatus (10) for establishing the positions of metal objects in a mixed input stream of both metal and non-metal objects, the apparatus comprising a differential metal-detecting coil (14A) having a first coil portion wound in a first sense and a second coil portion of generally similar shape and size to the first, wound in a second sense opposite to the first sense, and conveying means (11) for moving objects with respect to, and past, the differential metal-detecting coil in a plane and in a direction with unit vector â, characterised in that the second coil portion is displaced from the first coil portion by a displacement B having a component in the plane in a direction with unit vector {circumflex over (b)}, wherein 0 < cos - 1 ? a ^ · b ^ < ? 2 , and in that the apparatus further comprises analysing means for analysing the form of the output voltage of the coil as a function of time to establish the position of said metal objects in a direction ? in the plane, where ? is d

Abstract: A metal detection apparatus for detecting a metal object (13) beneath a surface (12a) of a human or animal body (12) comprises transmitter means (10) for generating a magnetic field in the vicinity of the metal object (13), thereby inducing currents within the metal object (13) to generate a secondary magnetic field, and detection means (14) for detecting the secondary magnetic field.

Abstract: Apparatus for detecting a metal object comprises a transmitter for generating a pulsed or an alternating magnetic field in the vicinity of the metal object to be detected and a detector for detecting the secondary magnetic field induced in the metal object by the transmitted magnetic field. The detector measures at least three magnetic field gradient components of at least first order of the secondary magnetic field. The apparatus also comprises a processor for determining at least one of the position or the electro-magnetic cross-section or an estimate of the shape of the metal object from the measured magnetic field spatial gradient components. The processor fits the measured components to dipole, multiple dipole, multipole, or extended source models. In a preferred embodiment, the invention may comprise three or more pairs of gradiometric coils, or other sensing means.

Abstract: A gradiometer for measuring properties of a magnetic field and in particular, for measuring magnetic field gradient components, comprising at least two magnetic sensors wherein at least two of the magnetic sensors are arranged to sense the magnetic field component in substantially the same direction. The magnetic sensors may be super conducting quantum interference device (SQUID) magnetometers, Hall probes, flux gates or magneto-resistive magnetometers. The gradiometer also includes a computer processor loaded with an adaptive signal-processing algorithm, for performing adaptive signal balancing of the magnetometer outputs. In a preferred embodiment the gradiometer may comprise at least eight magnetometers in a three-dimensional arrangement, and a set of three orthogonal global feedback coils, one for each direction x, y, z, such that the five independent magnetic field gradient components may be measured. The gradiometer may also be used to measure second or higher order magnetic field gradient components.