Abstract: In coded aperture imaging knowledge of the coded array pattern and its positional relation to the detector array is needed in order to be able to reconstruct the scene image. Usually a theoretical model of the coded array is used and the actual array needs to be aligned accurately with respect to the detector. The present invention uses a coded aperture imager to image a reference object in the scene and uses the intensity pattern on the detector array to determine the decoding pattern corresponding to the coded aperture array. The reference object may be a point source in which case the pattern on the detector array may be used directly as the decoding pattern or it may be used to correct a theoretical pattern for any misalignment.

Abstract: A random access decoder (114) comprising a plurality of decoder circuit elements (116), each decoder circuit element having a unique electronic address and a binary data output (122), means for applying an input signal (124) to each of the decoder circuit element and where each decoder circuit element places data on its binary data output (122) only when the unique electronic address of a particular decoder circuit element (116) matches the applied input signal (124) and wherein the unique electronic address of each of the plurality of decoder circuit elements (116) is electronically loaded into each of the decoder circuit elements (116). In one embodiment, each decoder circuit element (116) comprises equivalent components electrically connected in the same arrangement.

Abstract: A surface (30) suitable for promoting the formation of droplets of liquid (35) is provided comprising alternating regions of liquid repelling (32) and liquid attracting (33) material in at least one direction across the surface wherein the diameter of the droplets is controlled by the size of the smallest dimension of the liquid attracting material. The surface (30) may be textured and/or form a pattern. Also disclosed are a method and a system of collecting a liquid (35) carried by or condensed out of a vapor comprising passing a vapor across such a surface (30) and a method of purifying a liquid by passing a vapor containing droplets of a liquid over such a surface.

Abstract: A magnetic field sensor device (2) is described that comprises an oscillatory member (8) and current control means (6). The current control means (6) is arranged to pass an alternating current (AC) along at least first (10) and second (12) current paths provided through the oscillatory member (8) and is arranged to provide magnetic gradiometer mode operation (i.e. to measure magnetic field gradient) in which current flow through the first current path (10) is in substantially the opposite direction to current flow through the second current path (12). The current control means (6) can also prove magnetometer mode operation (i.e. to measure magnetic field strength). The magnetic field sensor (2) may be used in a compass.

Abstract: A micro-opto-electro-mechanical systems (MOEMS) electro optical modulator (2) having an electrically tuneable optical resonator comprising an asymmetric Fabry-Perot etalon incorporating a mirror (10) resiliency biased with respect to a substrate (13) and moveable in relation thereto in response to a voltage applied there-between. The optical modulator (2) is capable of modulating electromagnetic radiation having a plurality of wavelengths. The modulator is adapted to modulate the transmission of short wave infrared radiation (SWIR), medium wave infrared radiation (MWIR) and long wave infrared radiation (LWIR) and the reflection of visible radiation. A spatial optical modulator having a plurality of said MOEMS optical modulators (2). A method of addressing said spatial optical modulator.

Abstract: A radiation detection apparatus comprises a radiation detector and a lens arrangement. The lens arrangement comprises a polarising element and an optical corrector. The optical corrector is preferably located between the polarising element and the radiation detector and has at least one surface designed to correct optical aberrations present in the lens arrangement. The optical corrector may be arranged to provide a mechanical support to the polarising element. The optical corrector is arranged to increase a diffraction limited acceptance angle of the apparatus.

Abstract: A connector adapted to transfer microwave energy between two planes within 45° of perpendicular to one another, comprising a first member comprising a first conductor separated from a first conductive ground plane separated by a first dielectric, the first dielectric having a slot formed therein; and a second member comprising a second conductor separated from a second ground plane by a second dielectric, the second conductor being provided with an electrical connection to the second ground plane at a first end of the second member; in which the first end of the second member extends through the slot in the first member such that the electrical connection is positioned between first ground plane and first conductor. The connector may be a microwave antenna, in which case the first conductor forms a microstrip patch antenna. A method of producing such connectors and an array of such antennas is also disclosed.

Abstract: The present invention relates to processing of coded aperture images. Multiple frames of data acquired by the coded aperture imaging system, each with a different coded aperture array, are processed to form an image. The processing incorporates the constraints that the image solution must be positive and that the solution should be zero outside an expected image region. In one embodiment image enhancement may involve dividing the processed image into image regions having a spatially invariant point spread function and solving an inverse problem for each image region to reduce image blurring.

Abstract: Methods for coded aperture imaging, and processing the data from coded aperture imaging are taught. Several snapshots of an image are acquired, each using a different coded aperture array. The several snapshots are combined together with appropriate weightings to form a single equivalent frame as are the aperture functions for the coded aperture arrays used. Combining several frames of data can improve the signal to noise ratio of the decode image and increase the resolution of the image. Preferably a balanced weighting system is used and image reconstruction is performed by inverting the covariance matrix formed by the covariance of the signals from a number of estimated trial points. Using a balanced weighting system reduces the covariance matrix to a diagonal or near diagonal matrix with a corresponding reduction in computational load. The techniques also reduces additive noise.

Abstract: The present invention relates to an imaging system which employs the same principles as coded aperture imaging. High angular resolution coded aperture imagers require a small aperture size and relatively large spacing between the coded aperture array and the detector. At such high resolutions diffraction effects can start to dominate and can degrade image quality. The present invention provides a detector array which receives radiation from a scene via a coded diffractive mask. The coded diffractive mask is designed such that its diffraction pattern at the waveband of interest is a well conditioned coded intensity pattern having a strong autocorrelation function with low sidelobes. Thus radiation reaching the detector array is diffracted by the diffractive mask but in a defined way and it is the diffraction pattern of the mask which provides the coding.

Abstract: The invention provides methods for validating a position of an airborne platform, by comparing rate of change of a measure of barometric altitude with rate of change of a measure of geometric altitude. When the difference in rates of change exceeds at least one predetermined threshold an indication is provided that a threshold has been exceeded. The methods may be employed onboard an aircraft and/or at an air traffic control site, provided the aircraft transmits the necessary parameters. The comparison not only provides validation of vertical positioning information (altitude) but also horizontal positioning information. Corresponding apparatus, systems, programs for computers, and communications signals are also provided.

Abstract: This invention relates to a coded aperture imaging system wherein a detector array is arranged to receive radiation from a scene via a coded aperture mask. The coded aperture mask provides a plurality of uncorrelated coded aperture arrays at different positions on the mask. Each distinct coded aperture array therefore passes coded information to the detector array. The intensity pattern at the detector array, which is a summation of the intensity patterns from each of the distinct coded aperture arrays, can be decoded separately for each coded aperture array to reconstruct a separate image associated with each coded aperture array. In this way the present invention teaches a coded aperture array means with multiple, simultaneous fields of view. The different fields of view can be different sizes and/or resolutions. Preferably the coded aperture mask is reconfigurable.

Abstract: A liquid crystal device comprises a layer (2) of a nematic liquid crystal material contained between two cell walls (3, 4) each carrying electrode structures (6, 7) and an alignment surface (20, 21). The alignment layer (20, 21) on one or both cell wall (4), is formed of a plurality of small (<15 ?m) surface features each separably capable of providing a bistable pretilts and an alignment direction and collectively causing larger variations of molecular orientation across the layer (2). The device may be switched between a light transmissive state and a light non-transmissive state. The small surface features may be areas of grating (21), protrusions (25), or blind holes (26), separated by mono stable flat surfaces (Fm) coated with a homeotropic alignment layer. Preferably, the grating etc provides bistable switching operation between a low surface tilt and high surface tilt, and the low tilt alignment direction varies between adjacent grating areas.

Abstract: A micro electromechanical system (MEMS) switch includes a fixed contact (24) and a moveable contact (35) on an armature (30). The switch has electrodes (22, 34) associated with both the fixed and moveable contacts for providing an electrostatic switch operation and piezoelectric material with associated electrodes (36, 40) for bending the armature upon application of an electric voltage and providing an initial piezoelectric switch operation followed by electrostatic switching and clamping. The armature is of curved shape which is bent away from the fixed contact when in a switch open condition with zero applied voltage. This gives a large, e.g. 3 pm, switch gap in an OFF state which is reduced by piezoelectric operation suitable for electrostatic switch closing. A curved condition is provided by varying strain across the armature thickness, and is produced during manufacture of the switch.

Abstract: A liquid crystal device comprises a layer (2) of a nematic liquid crystal material contained between two cell walls (3, 4) each carrying electrode structures (6, 7) and an alignment surface (20, 21). The alignment layer (20, 21) on one or both cell wall (4), is formed of a plurality of small (<15 ?m) surface features each separably capable of providing a bistable pretilts and an alignment direction and collectively causing larger variations of molecular orientation across the layer (2). The device may be switched between a light transmissive state and a light non-transmissive state. The small surface features may be areas of grating (21), protrusions (25), or blind holes (26), separated by mono stable flat surfaces (Fm) coated with a homeotropic alignment layer. Preferably, the grating etc provides bistable switching operation between a low surface tilt and high surface tilt, and the low tilt alignment direction varies between adjacent grating areas.

Abstract: The use of a mesogenic compound having a terminal end chain comprising carbon, oxygen, or sulphur, which has at least one pendent C1-4alkyl, C1-4alkoxy or a cycloalkyl ring, arranged no more than 6 atoms from the end of the chain either decreasing the melting point, increasing the clearing point, increasing the speed of switching and/or increasing the tilt angle of a liquid crystal mixture. Examples of such compounds are of formula (I) where M is a mesogenic core group, and X and Y are terminal groups, provided that at least one group X or Y is a group of sub-formula (i) where Z1, Z2, R1, R2, R3, R4, R5, R6, R7, s, q, m and n are as defined in the specification. Novel compounds of formula (I) are also described and claimed.

Abstract: A drive configuration for a skid steered vehicle incorporates a controlled differential for use in exercising steering control of the vehicle, comprising a compound planetary gear set (8) coupling two shafts (7a, 7b). Respective sun gears (10a) and (10b) turn with the shafts and mesh with compound planet gears (12) in a common planet carrier (13), the ratios of the number of gear teeth between each sun gear and the respective gears (14a) or (14b) of the compound planets being unequal so that when the planet carrier is stationary the two shafts are coupled through the differential to turn together in the same sense but with a speed difference, and controlled rotation of the planet carrier varies the speed difference between the shafts in accordance with the sense and speed of rotation of the planet carrier.

Abstract: This invention relates to a proximity sensor. An illumination means (2) projects an array of spots (40) towards a scene. Detector (8) looks towards the scene through a mask (6). The mask (6) is arranged such that light from a target at a certain range, for instance far object (14) is not transmitted to the detector. Light reflected from a close object (16) however passes through the mask (6) and is incident on the detector (8). A rise in the intensity of incident light at the detector (8) is determined by threshold detector (10) and used to operate an alarm (12).

Abstract: This invention relates to the control of radiant thermal energy and more specifically to highly Thermal Infrared (IRT) reflective pigments for use in decorative coatings for buildings or other areas where the control of IRT energy and visual decoration are required. Control of the spread of thermal energy in domestic building through passive techniques reduces energy consumption by reducing reliance on heating in cool environments and cooling air-conditioning in warm environments. A number of paint formulations having low emissivity in the thermal infrared exist which are based on variants of conventional decorative paint fluids. There are a number of problems associated with such formulations such as susceptibility to damages and high emissivity for certain colour pigmentations. The present invention proposes a low emissivity flake (1) for use in a paint formulation which substantially overcomes the problems associated with the prior art.

Abstract: Low frequency vibration induced noise is reduced in a towed sonar array of the type comprising a number of oil-filled modules joined end to end with each module housing a plurality of hydrophones by arranging that the signal output from each hydrophone in an array is equally weighted at low frequencies to form a single channel. Beamforming is then carried out by applying different weights to the different module channels. High modulus internal strength members are included in each module to resist anti-phase vibration of the couplings at the end of the module. The hydrophone spacing and the coupling lengths are both made small compareed to the module length to improve vibration noise reduction.