Abstract: In a method of multi-level spatial light modulation, using a weighted bit plane technique where an n-digit binary number represents the intended grey level of each pixel location in an array of binary pixels, representative binary numbers are altered to closely adjacent values such as to reduce the inequality of 1s and 0s therein. The method may be applied to a single frame so modifying the gray scale somewhat, or a multi-frame method may be used in which at least some binary numbers are altered to different values in different frames for reducing the inequality of 1s and 0s over the set of frames, while maintaining or approximating the gray scale value as a time average. The methods are particularly useful for maintaining or approximating pixel-wise dc balance in liquid crystal spatial array modulators.

Abstract: In a method of signal processing for greyscale imaging in which weighted bitplanes corresponding to a greyscale image are stored as binary strings in sequential locations in a memory, in decreasing order of intended duration (weighting), a number of read passes equal to the number of weighted bitplanes are made from the set of stored bitplanes, each pass commencing with the highest order bitplanes and continuing along the stored bitplanes in sequence, the lengths of the sequences being varied and selected such that at the end of the said number of read passes each bit plane has been read out a plurality of times proportional to or equal to its duration (weighting). The method has utility in driving high speed liquid crystal matrix arrays particularly where each bitplane needs to be refreshed. A small ac potential may be applied to the array between writing steps.

Abstract: This invention relates to the field of lasers and in particular to the pump sources used in lasers. Many existing lasers use linear flashlamps in order to create population inversion in the gain medium of the laser. Such pump sources suffer from a number of drawbacks particularly when pumping dye lasers including explosive damage, long optical pulse length and inappropriate spectral emission. This invention provides a pump source for a laser which exploits the surface discharge phenomenon. A dielectric material (1) which is in contract with a gas (9) has electrical energy discharged across its surface in order to provide an electromagnetic emission which is then used to pump the gain medium. By varying the dielectric material or the cover gas used (amongst other variables) the surface emission can be used to pump the laser gain medium.

Abstract: A method of reclaiming a metal M1 from a source of highly contaminated metal M1X having a high oxygen content includes the steps of: sintering the highly contaminated finely divided metal M1X into a perform; introducing the preform into an electrochemical cell, the cell containing a liquid electrolyte comprising a fused salt or mixture of salts generally designated as M2Y in which oxygen is soluble, and a relatively inert anode; conducting electrolysis under conditions favorable to the selective dissolution of oxygen in preference to the deposition of the M2 cation to form a decontaminated metal preform; and following electrolysis, reclaiming the decontaminated metal preform from the cathode. The reclaimed decontaminated metal preform may optionally be crushed to yield a powder of the metal M1. The highly contaminated finely divided metal may comprise swarf, chips and such-like from machining operations, or may comprise high oxygen content metal powders such as hydride-dehydride (HDH) titanium powder.

Abstract: A receiver front end is provided capable of receiving electromagnetic wave signals having frequencies in the range of substantially 55 GHz to substantially 65 GHz, and having a gain of substantially 8 dB or above and a noise figure of substantially 4.5 dB or below, and comprising one or more multifunction monolithic microwave integrated circuits (MMICs). The or each MMIC may comprise a low noise amplifier (1), a sub-harmonic mixer (2), and an amplifier (3) for a reference signal for the sub-harmonic mixer.

Abstract: A method of removing oxygen from a solid metal, metal compound or semi-metal M1O by electrolysis in a fused salt of M2Y or a mixture of salts, which comprises conducting electrolysis under conditions such that reaction of oxygen rather than M2 deposition occurs at an electrode surface and that oxygen dissolves in the electrolyte M2Y and wherein, M1O is in the form of (sintered) granules or is in the form of a powder which is continuously fed into the fused salt. Also disclosed is a method of producing a metal foam comprising the steps of fabricating a foam-like metal oxide preform, removing oxygen from said foam structured metal oxide preform by electrolysis in a fused salt of M2Y or a mixture of salts, which comprises conducting electrolysis under conditions such that reaction of oxygen rather than M2 deposition occurs at an electrode surface. The method is advantageously applied for the production of titanium from Ti-dioxide.

Abstract: A focal plane detector for imaging objects within a scene and having integral processing means for detecting edges of objects within the scene. The focal plane detector comprises a plurality of detector elements arranged to measure the intensity of the electromagnetic radiation incident thereon and processing means integral to the focal plane detector for combining the intensity measurements so as to indicate the difference in the intensity of the electromagnetic radiation. The focal plane detector is arranged such that the output from the focal plane detector corresponds to edges of objects within the scene. The focal plane detector may be arranged to be sensitive to infrared radiation.

Abstract: A method is provided of analysing the composition of a semiconductor material (3) comprising irradiating the material with energy from an energy source (1) which energy is diffracted from the material, detecting one or more portions of the diffracted energy, and analysing the or each detected portion to obtain a parameter indicative of the intensity of the or each portion. The or each portion of the diffracted energy detected may be a quasi-forbidden reflection diffracted from the material, e.g. may be a (002) reflection diffracted from the material, or a (006) reflection. The detection of the or each portion of the diffracted energy may take place at one or more detection angles (9), or at all angles of reflection/transmission of the diffracted energy source, or at a range of angles around one or more detection angles. The energy source may comprise a beam of x-rays produced by an x-ray tube (2), and one or more detectors (4) may be used to detect the or each portion of the diffracted energy.

Abstract: Radiometers detect radio wavelength electromagnetic radiation and typically have an antenna (16), an amplifier (18) and a detector (20). All three of these components have response characteristics that may be dependent on temperature, and in the case of systems using radiometer arrays dependent upon temperatures throughout the system. Different temperatures across a multi-channel antenna and differential channel temperature response can result in poor image quality from imaging radiometers. Resolution of a linear array of detector horns is limited by the size of the horns.

Abstract: This invention relates to the field of Inertial Navigation Systems (INS) and satellite navigation systems such as the Global Positioning System (GPS) and in particular relates to methods of integrating GPS and INS data in order to provide more accurate navigation solutions. The invention provides a method of improving the accuracy of a tightly coupled integrated INS and satellite radio navigation system in cases where the satellite navigation receiver has adaptive tracking loop bandwidths.

Abstract: A method of blind signal separation of convolutively mixed signals comprises firstly processing signals to produce second order independence. In a second step, and together with ranges of signal delay and rotation parameters, the resulting processed signals are used to determine delay and rotation parameters. These parameters implement at least one elementary paraunitary matrix and transform the processed signals into output signals with improvement in independence to at least a predominant part of a maximum extent obtainable over the parameter ranges. The output signals then become the next processed signals and the second step is iterated until independence ceases to be improved significantly. The latest output signals are then unmixed signals.

Abstract: A receiver front end is provided capable of receiving electromagnetic wave signals having frequencies in the range of substantially 35 GHz to substantially 40 GHz, and having a gain of substantially 24 dB or above and a noise figure of substantially 4 dB or below, and comprising one or more multifunction monolithic microwave integrated circuits (MMICs). The receiver front end preferably has a noise figure of substantially 4 dB or below over an output signal frequency range of substantially 1 to 10 GHz, and a size in the region of 30 mm2 or less. The reveiver front end may comprise a receiver MMIC, and a doubler/buffer amplifier MMIC. The receiver MMIC may comprise a low noise amplifier (3), a mixer (5), a filter (4) and an intermediate frequency amplifier (6).

Abstract: A system for imaging the contents of containers includes an imager arranged to receive millimetre wave radiation from a reception volume through a receive antenna wherein, in use, the container is moving relative to the receive antenna, the reception volume is positioned such that the relative movement causes the reception volume to move through the container; data from the antenna is recorded as the reception volume moves through the container, and an image of the contents of the container is built up from the recorded data. The system is particularly suitable for imaging containers mounted on vehicles. The imager may advantageously be mounted in a portal, allowing convenient and controllable relative positioning of the container, and allowing the relative speed to be controlled or measured easily. The invention allows 3D or pseudo 3D images to be produced to aid identification of container contents. The invention also includes a method for imaging.

Abstract: An optical phase detector comprising coupling means for receiving two optical inputs and for producing two combined optical outputs, means for detecting the two combined optical outputs and producing two corresponding electrical signals, and means for measuring the difference between the two electrical signals and generating an output difference signal which may be used to provide an indication of the phase difference between the two optical inputs. The optical phase detector comprises a voltage-tuneable electro-optic phase modulator for modulating the phase of an optical input to the optical phase detector to provide a linearized response. In this arrangement the output difference signal may be maintained at a constant level by varying the voltage applied to the electro-optic phase modulator, the applied voltage providing an indication of the phase difference between the two optical inputs. Applications include frequency discriminators, various sensors, and a laser stabilization apparatus.

Abstract: An electroluminescent device (10) comprises a porous silicon region (22) adjacent a bulk silicon region (20), together with a top electrical contact (24) of transparent indium tin oxide and a bottom electrical contact (26) of aluminium. The device includes a heavily doped region (28) to provide an ohmic contact. The porous silicon region (22) 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 (10) has a rectifying p-n junction within the porous silicon region (22).

Abstract: A mainly bainitic steel having the following composition in weight percent: carbon 0.6-1.1; silicon 1.5 to 2.0; manganese 1.8 to 4.0; chromium 1.2 to 1.4; nickel 0-3; molybdenum 0.2 to 0.5; vanadium 0.1 to 0.2, balance iron save for incidental impurities.

Abstract: An optical inspection system (10) for comparing surface structures of test and reference objects comprises a laser (12), a photorefractive crystal (24) and a detector (30). A refractive index grating corresponding to a diffraction pattern of a surface structure of the reference object is present within the photorefractive crystal (24) and acts as a spatial filter for light diffracted by surface structures of the test objects. If a surface structure of a test object matches that of the reference object, little or no light reaches the detector (30). If the surface structure of a text object differs from that of the reference object, light of greater power reaches the detector (30). The system (10) provides a simple pass/fail comparison test and light incident on the detector (30) requires no interpretation or other processing. The system (10) may be adapted to allow simple imaging of an edge of an object.

Abstract: This invention relates to the filed of land mines and in particular to devices and techniques for neutralising and/or retrieving land mines. Existing mine retrieval/neutralisation techniques includes 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. and 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 excavation technique that involves excavation of the mine by means of an explosive charge.

Abstract: An apparatus for facilitating the alignment of an optical fiber to an integrated waveguide component comprising a substrate having an integral waveguide comprises a mask arranged to be disposed between the optical fiber and the integrated waveguide component, wherein the mask includes an aperture extending therethrough. In use, the aperture is substantially exactly aligned with the waveguide thereby to permit light from the optical fiber to be transmitted to the waveguide but to substantially prevent light from the optical fiber from passing around the waveguide and/or through the substrate.