Abstract: An apparatus for detecting a moving ferromagnetic target object in a protected area comprises a first magnetic sensor adapted to measure a magnetic field within a first localised volume of space defined by a first zone of sensitivity of the first magnetic sensor and to produce a corresponding first measurement signal, and a second magnetic sensor adapted to measure a magnetic field within a second localised volume of space defined by a second zone of sensitivity of the second magnetic sensor and to produce a corresponding second measurement signal. The two magnetic sensors are separated spatially by a baseline such that the overlap between the two zones of sensitivity defines both a protected zone and a non-protected zone.

Abstract: An apparatus for detecting a moving ferromagnetic target object in a protected area comprises a first magnetic sensor adapted to measure a magnetic field within a first localised volume of space defined by a first zone of sensitivity of the first magnetic sensor and to produce a corresponding first measurement signal, and a second magnetic sensor adapted to measure a magnetic field within a second localised volume of space defined by a second zone of sensitivity of the second magnetic sensor and to produce a corresponding second measurement signal.The two magnetic sensors are separated spatially by a baseline such that the overlap between the two zones of sensitivity defines both a protected zone and a non-protected zone.

Abstract: An infrared detector comprising a plurality of bolometer detectors, bias circuitry for applying a bias to the bolometer detectors, and connectors for connecting the bolometer detectors together to form a network, wherein the bolometer detectors are arranged in an environment at substantially atmospheric pressure. A method for increasing the sensitivity of an infrared detector, having a plurality of bolometer detectors arranged in an environment at substantially atmospheric pressure so as to at least partly compensate for a reduction in the sensitivity of the infrared detector due to conduction of thermal energy from the bolometer detectors through the environment, the method comprising at least one of the steps of connecting the bolometer detectors together in at least one of series and parallel, and operating the bolometer detectors at a DC bias current.

Abstract: An imager is disclosed comprising: one or more detectors, a shutter adapted to open and close periodically to modulate the radiation incident upon the detector element to produce a sequence of alternating open fields and closed fields, said detector being adapted to produce a first pair of output signals Vo1 and Vc1 comprising an open field and a closed field, and a second pair of output signals Vo2 and Vc2 comprising an open and a closed field, a reset device adapted to reset the output of the detecting element to a predetermined voltage after the output signals of Vo1, Vc1, Vo2 and Vc2 have all been obtained, there being no reset of the output of the detecting element between the output signals Vo1, Vc1, Vo2 and Vc2, and a processor adapted to process said first and second pairs of output signals to produce a first and a second processed image signal from the detecting element, the first processed image signal corresponding to the first pair of fields and the second processed image signal corresponding to t

Abstract: A non-mechanical modulating device for use in infrared detection. The device is of particular use in the 8-14 &mgr;m range and has application in thermal imaging cameras and gas sensing systems. The modulator comprises a germanium element and a means of varying the carrier concentration. In particular, the variation of the hole concentration gives rise to the absorption of infrared radiation due to interband transitions between the light and heavy hole bands in the split valence band in germanium. The variation in hole concentration may be initiated in any convenient way, for example, by the irradiation of the germanium with visible or near infrared light, by the electrical injection of free carriers across a germanium diode structure or by electron impact on the germanium surface following acceleration under vacuum. In the case where the variation in carrier concentration is initiated by optical means, the surface of the germanium is treated so as to produce a low surface recombination velocity.

Abstract: The invention relates to a fragment of DNA containing genes encoding the synthesis of the O-antigen of Vibrio cholerae serotypes Inaba or Ogawa and being at least 16 kb in length. The invention further related to a cosmid comprising a cloned DNA fragment containing genes encoding the synthesis of O-antigen of Vibrio cholerae serotypes Inaba or Ogawa and to a strain of E.coli that includes the fragment.

Abstract: A thermal detector comprises a row of thermal detector elements each connected to a common bus line via the gate of a high impedance input preamplifier and a switch. The line output from the bus line is taken across a load resistance providing a common source follower load for the prepamplifiers. The signal across the load is passed through an anti-aliasing low-pass filter to a sample-and-hold. Signals then pass to a high-pass digital filter arranged to substract successive signals from each detector element corresponding to open and closed positions of a radiation modulator. This attenuates 1/f noise. The filters are located outside the row. Bulky filter components may accordingly be employed giving good noise performance without affecting detector element spacing. The preamplifiers and the switches are preferably MOSFETs. The detector may incorporate many rows of detector elements to provide a two-dimensional array.