Abstract: A method of anomaly detection applicable to telecommunications or retail fraud or software vulnerabilities uses inductive logic programming to develop anomaly characterisation rules from relevant background knowledge and a training data set, which includes positive anomaly samples of data covered by rules. Data samples include 1 or 0 indicating association or otherwise with anomalies. An anomaly is detected by a rule having condition set which the anomaly fu,lfils. Rules are developed by addition of conditions and unification of variables, and are filtered to remove duplicates, equivalents, symmetric rules and unnecessary conditions. Overfitting of noisy data is avoided by an encoding cost criterion. Termination of rule construction involves criteria of rule length, absence of negative examples, rule significance and accuracy, and absence of recent refinement.

Abstract: An image processing system includes a plurality of vertically arranged linear arrays of detectors imaged onto a plurality of areas in a scene of interest. Horizontal movement of an object through the plurality of areas of interest are detected and fed into a processor. The processor may detect object range, direction of movement, speed, true direction of travel, object type. The detectors may be sensitive in the infra red (IR), microwave (including mm wave devices), or visible wavebands, operating with ambient or artificial illumination. In some application a combination of IR and visible detectors may be used. Preferably each detector in the linear array has an associated amplifier and filter. A 360° cover may be obtained by combining several systems into a single unit. The system may be used to detect objects and then control operation of a higher definition two-dimensional detector array and camera.

Abstract: A MEMS incorporating a sensing element and a JFET electrically connected to the sensing element is fabricated by the steps of: forming a first layer of electrically insulating barrier material on a surface of a substrate; patterning the first layer so as to expose a first region of the substrate; doping by ion implantation the first region of the substrate to form a well region of the JFET; forming a second layer of barrier material on the surface of both the first layer and the first region of the substrate; patterning the barrier material so as to expose a part of the first region of the substrate; doping by ion implantation the exposed part of the first region of the substrate to form source and drain contact areas of the JFET; patterning the barrier material so as to expose a second region of the substrate; and doping by ion implantation the second region of the substrate to form gate and substrate contact areas of the JFET in a single implantion step.

Abstract: Optical circuits for optical amplifier input and output stages are described. The input stage circuit (42) comprises a first optical waveguide (46) for carrying a signal beam to be amplified, a second optical waveguide (62) for carrying a pump beam, a beam combining means (58) optically coupled to the first and second optical waveguides (46, 62) for producing a combined signal/pump beam, and means for optically coupling the combined signal/pump beam into an amplifying optical fibre (63). The output stage circuit (44) comprises a first output optical waveguide (64), an optical fibre attachment means arranged to receive an amplifying optical fibre (63) and an optical fibre attachment means arranged to receive an output optical fibre (76) wherein light from the amplifying optical fibre (63) is optically coupled to the output optical fibre (76) via the first output optical waveguide (64).

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 method of querying a structure of compressed data comprising records stored as a forest of binary includes the step of generating an instruction set allowing a specified data value with a binary tree to be retrieved, given input of an address in memory that identifies the binary tree. Further querying functions which utilise the instruction set allow selection of records on the basis of one or more specified data values, or ranges of data values, statistical analysis of records and grouping of records on the basis of common data values within fields of records.

Abstract: A guided underwater object (GUO) (100) comprises steering means, an on-board guidance system (200) for controlling the steering means, and a hydrophone unit or units (104A, 104B, 104C, 104D, 104E, 104F, 104G, 104H) arranged to pass signals induced therein by an acoustic guiding beam to the on-board guidance system to effect directional control of the self-propelled underwater object. The GUO is guided by a remote guidance system characterized by a plurality of transmitter arrays (402A, 402B, 402C, 402D; 412A, 412B, 412C, 412D; 422P, 422Q, 422R) arranged to transmit a plurality of contiguous acoustic beams (302A, 302B, 302C, 302D) each having a different frequency or frequency chirp (or other acoustic signal coding) and enclosing a guidance corridor of lower sound level (‘null’) (304) extending approximately in the direction of propagation of the acoustic beams and defining a flight path of the object.

Abstract: A holographic display comprises a spatial light modulator, SLM, arranged to display a set of tiled holographic images, and illuminating means for illuminating a surface of the SLM. Replay means are provided for focusing light reflected from the SLM surface to present a three dimensional image. The illuminating means comprises a light source appearing substantially at a DC spot position of the replay means.

Abstract: The invention relates to the field of land mines and in particular to devices and techniques for neutralising and/or retrieving land mines. Existing mine retrieval/neutralisation techniques include mechanical excavation or shaped charge attack and such techniques are either susceptible to blast damage in the event of inadvertent mine explosion or can produce ambiguous results (i.e. an operator can be unsure as to whether a mine has been successfully attacked or a non-mine target has been attacked in error). The present invention provides a mine retrieval technique that involves spearing the mine for later retrieval to the surface.

Abstract: The invention provides an improved means for displaying computer generated hologram (CGH). Images appearing in the image volume are realised as a set of planar facets that approximate to the shape of the original object to be displayed. These facets are populated with points, that act as the visible parts of the displayed image. When an object is displayed, certain facets will not be face on the viewing zone. This will result in an apparent surplus of points on these facets, which is wasteful of computing effort. The current invention thus provides for certain facets to be denuded of points if these facets are not presented face on to the viewing zone of the CGH. The invention is mainly applicable for producing CGHs using the interference based algorithm, but can also be used in other types of 3D display that make up objects from an array of points.

Abstract: A sensor module for use in a sensor network is described. The sensor module carries one or more sensor element, such as microphones or imaging devices, for detecting events in use. The sensor module has a locator for determining its location and preferably an orientation sensor for determining it location and a transceiver for communicating with other modules in the network or with a base station. The module also has a processor which is adapted such that, in use, the module communicates with other sensor modules and determines whether to operate in a sensing mode to detect events or a controlling mode. In this way a self organizing adaptive network is provided. The invention is particularly useful for rapid area deployment resulting in random placement such as by gun launch or air drop as once all the modules are deployed the network will work out which modules should act as sensor nodes and which should act as controlling nodes so as to maximise network efficiency.

Abstract: An apparatus for redirecting radiation including a polarization dependent reflector and an optical component able to transform the polarisation of radiation as it passes through the component. Radiation having a first polarisation component impinging upon the reflector from a source is reflected towards a scene area. Radiation not having this polarisation component passes through the reflector. The radiation having the first polarisation is then transmitted towards a scene via the optical component. As the radiation passes via the optical component, reflects back from the scene and passes again via the optical component, the polarisation is changed to state where it can now pass through the polarisation dependent reflector. The apparatus allows a scene to be illuminated as if the illuminator were positioned at the viewpoint of an imaging system, and so aids uniform illumination of the scene.

Abstract: A glass fiber (22) has a core (24) provided with Raman laser effect particles (28) embedded in a glass matrix (30), with glass cladding (26) around the core. The refractive index of the glass matrix (30) is matched to that of the Raman laser effect particles (28) so as to avoid scattering. It is not necessary to have a single crystal of Raman laser material to create a laser effect in the glass fiber. A length of fiber in the order of meters or tens of meters can produce optical laser light. It is possible to have a single fiber (22) emit laser light at different frequencies due to Stokes and Anti-Stokes emissions. A simple laser device can therefore produce several colors of laser beams.

Abstract: In a field effect transistor having a quantum well is provided by a primary conduction channel, at least one secondary conduction channel immediately adjacent and in contact with the primary channel has an effect bandgap greater than the effective bandgap of the primary channel, and the modulus of the difference between the impact ionisation threshold IIT of the primary channel and the effective conduction band offset (the height of the step) between the primary and secondary channels being no more than 0.5 Eg (effective), or (alternatively) no more than 0.4 eV. Higher energy carriers which might otherwise cause impact ionization leading to runaway are thus diverted into the secondary channel allowing the device to run faster at increased voltages and/or to exhibit much greater resistance to runaway. The primary channel is prefereably of low bandgap material, for example InSb, InAs, InAs1-y, In1-xGaxAs.

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 â·{circumflex over (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 defined by â·?=0.

Abstract: A method of generating a binary computer generated hologram for use in displaying a holographic image, the method comprising the steps of generating a complex modulation computer generated hologram corresponding to a desired reply object, transforming the complex modulation computer generated hologram into a real positive computer generated hologram, and transforming the real positive computer generated hologram into a binary computer generated hologram by comparing each element of the real positive computer generated hologram with at least one neighboring element and replacing the compared element with a binary value which depends upon the result of the comparison.

Abstract: An electroluminescent device comprises a porous silicon region adjacent a bulk silicon region, together with a top electrical contact of transparent indium tin oxide and a bottom electrical contact of aluminium. The device includes a heavily doped region to provide an ohmic contact. The porous silicon region is fabricated by anodizing through an ion-implanted surface layer of the bulk silicon. The silicon remains unannealed between the ion-implantation and anodization stages. The device has a rectifying p-n junction within the porous silicon region.

Abstract: An optical transmission system includes an optical source such as a laser having an optical output, this optical output being modulated such that it has periods of operation having a first set of characteristics interspersed with periods of operation having a second set of characteristics. The output is then split into at least two signals, and one of the signals delayed with respect to the other signal before the two are mixed, such that a portion of the modulated optical output having the first set of characteristics in one of the signals corresponds with a portion of the modulated optical output having the second set of characteristics of another of the signals. This allows a single optical source to provide to a receiver a local oscillator signal simultaneously with a data carrying signal. The system is particularly suitable for lidar applications, including gas sensing, but also has utility in data communications systems.

Abstract: A phoretic display device comprising a plurality of electrophoretic or magnetophoretic cells, each having a phoretic particle dispersed within a suspension medium comprising a liquid crystal material. The phoretic cell is adapted to induce defects, sometimes known as disclinations, in the alignment of the liquid crystal material within the cell which act to exert a retentive force on the phoretic particle when within the region of influence of the defects. The configuration of the display introduces a threshold level in the electric or magnetic field required to move the phoretic particle between defects within the cell. Accordingly, the non-linear electro-optic or magneto-optic behaviour of the display facilitates matrix addressing of the cells therein. The display may comprise a plurality of prolate spheroid phoretic cells arranged in an encapsulant, the major (long) axis of each cell arranged substantially perpendicular to the plane of the display.

Abstract: A traveling wave amplifier (TWA) comprising two or more amplification modules, the inputs of adjacent amplification modules being connected together by a first inductance component of a first characteristic impedance, a second inductance component of a second characteristic impedance and a third inductance component of substantially the first characteristic impedance, the first characteristic impedance being greater than the second characteristic impedance. The outputs of adjacent modules may be similarly connected together by first, second and third inductance components. The characteristic impedance of the second inductance components is preferably substantially equal to that of the circuits to which the TWA is connected, e.g. 50?. The first and third inductance components have a characteristic of 100?. Such a TWA allows balancing of phase velocities between inputs and outputs of the amplification modules, connection of these around via holes, and extends the frequency capability of the TWA.