Abstract: A sensor having a detector array is provided with means for determining whether the normal field of view of the sensor has been obscured. The image output from the detector array is compared by a processor to an image of the normal filed of view, previously acquired and stored in a memory. Where there are significant differences between the images the processor activates an alarm. The location of high spatial frequency detail in the image may be compared and the absence of such detail used to give an indication that the sensor may be masked.

Abstract: Interrogation of a phase based transducer is performed by temporally overlapping and interfering a single pulse output from the transducer to determine the rate of change with time of the measurand represented as a phase change. The rate of change, or derivative of the phase change typically has a much smaller amplitude than the signal itself, and the derivative measurement therefore has reduced sensitivity. In this way, large amplitude signals which might otherwise be subject to overscaling effects can be measured more effectively.

Abstract: A fiber-optic surveillance system (10) includes a fiber-optic sensor (15) comprising a serial array (15) of fiber-optic point-sensors (16), successive point-sensors being linked by a distributed fiber-optic sensor (18). The system allows the location of intruder events along the sensor to be determined, and provides a reduction in the incidence of false-alarms compared to prior art systems.

Abstract: Methods and apparatus for tracking objects in conduits, especially for tracking the movement of a pig in a pipeline, are disclosed. Distributed acoustic sensing is used to obtain signal returns from a plurality of discrete longitudinal sensing portions of a fibre optic cable which is laid along the length of the conduit. The method involves detecting an acoustic signature corresponding to the object moving in the conduit. The acoustic signature may comprise a series of pressure pulses caused by the object traversing joints etc. in the conduit. Preferably the method involves detecting pressure waves caused by the object as it moves through the conduit. Detecting the characteristic pressure wave signal provides discrimination of the object from other acoustic disturbances. In pipeline applications a pig can be tracked in real time, if the pig stops moving an alert can be generated and the location of the pig will be known.

Abstract: In a transistor in which the majority carriers are holes, at least one narrow bandgap region or layer is doped p-type or contains an excess of holes and is subject to compressive mechanical strain, whereby hole mobility may be significantly increased. In a p-channel quantum well FET, the quantum well InSb well p-type layer 5 (modulation or directly doped) lies between In1-xAlxSb layers 4, 6 where x is of a value sufficient to induce strain in layer 5 to an extent that light and heavy holes are separated by much more than kT. Transistors falling within the invention, including bipolar pnp devices, may be used with their more conventional electron majority carriers counterparts in complementary logic circuitry.

Abstract: An apparatus (2) for the deployment of fascines comprises a fixed framework adapted to be mounted to the front region of a vehicle such as the glacis plate (3) of a tank (1). A leading portion of the framework extends forwardly of the vehicle and carries straps (18, 19) to support a bundle of inflatable fascine members (20). A winch (21) is mounted on the framework and can be used to raise the fascine members into the straps and subsequently to release the straps and allow the fascine members to drop into a ditch or other discontinuity and then inflate, to facilitate passage of the vehicle.

Abstract: A method of reconstructing an image of a scene (4) from data output by a detector (8) in a coded aperture imaging system (2) comprises taking multiple frames of data using a different coded aperture array 6 for each frame. For each frame of data a decoding pattern is employed which is point source diffraction pattern corresponding to the coded aperture array used to acquire that frame. The decoding patterns are combined in a Gram matrix. A two-dimensional to one-dimensional mapping is applied to the frames of data. A solution to the data is constructed which is related to the scene (4) by an integral operator. The integral operator has an averaging kernel with a main lobe width which is smaller than the detector pixel size. Processing of the data yields an image which has sub-pixel resolution, i.e. resolution greater than the native resolution of the detector (8).

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 buildings 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 damage and high emissivity for certain color pigmentations. The present invention proposes a low emissivity flake for use in a paint formulation which substantially overcomes the problems associated with the prior art.

Abstract: An RF screening apparatus comprising a scanning chamber and an RF inspection device or reader, the chamber having chamber walls which are substantially reflective to radiation at a frequency of operation. The chamber walls or at least a portion of the chamber walls may be visually transparent. This enables visual inspection and identification of the occupant and RF interrogation to be performed, substantially simultaneously if desired. RF interrogation signals produced by the reader reflect off the chamber walls, approaching a target tag from an increased number of different angles, thus increasing the chance of a successful read.

Abstract: A method of classifying an object, in particular of classifying a vehicle by evaluating the degree of correlation between an image data set corresponding to an image of at least part of the vehicle and each of a plurality of reference data sets each of which corresponds to a reference image of a vehicle comprises the steps of establishing the vehicle's aspect and selecting the plurality of reference data sets from a larger group of such data sets on the basis of the vehicle's aspect. By selecting from the larger group only those reference data sets which correspond to the vehicle's aspect, faster classification is achieved for a given level of processing resources. Alternatively, for a given processing or classification rate, the level of processing resources may be reduced compared to the prior art.

Abstract: An optical modulator comprising a spacing-controllable etalon having at least one sprung micro-mirror suspended above a substrate. At least one electrically insulating stop is provided between the micro-mirror and the substrate to avoid short-circuit when the micro-mirror is drawn towards the substrate by an applied voltage. An optical detector detects the time of arrival of a first laser pulse. A control circuit predicts from this an arrival time of the next incident laser pulse and, responsive to a control signal, either retains the micro-mirror in its pulled-down state held against the insulating stops or releases the micro-mirror at a time predicted to maximise or minimise the light transmitted through the modulator. After a time interval calculated to permit a predetermined number of mechanical oscillations, the micro-mirror is pulled back down onto the stops.

Abstract: An electronic circuit breaker including a two stage detection mechanism; an instantaneous trip operating at a first threshold and a delayed trip such operating at a second lower threshold. This is advantageous in maintaining operation during very short transient load peaks, which do not warrant isolation from the supply. The breaker can be line powered, can be reset remotely by controlling the line power, and can be implemented entirely in solid state electronics. As such it requires little or no service or maintenance.

Abstract: The present invention relates to an improved quantum key device for use in quantum key distribution, which device comprises a quantum detector unit for detecting a quantum signal and a plurality of logic units operably connected to the quantum detector unit wherein each logic unit is arranged to derive a separate quantum key from the quantum signal detected. In this way, a single quantum key distribution (QKD) receiver can generate separate quantum keys for separate users.

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: A method for completing an oil and gas well completion is provided. The perforators (10, 11) may be selected from any known or commonly used perforators and are typically deployed in a perforation gun. The perforators are aligned such that the cutting jets (12, 13) and their associated shockwaves converge towards each other such that their interaction causes increased fracturing of the rock strata. The cutting jets may be also be aligned such that the cutting jets are deliberately caused to collide causing further fracturing of the rock strata. In Ian alternative embodiment of the invention there is provided a shaped charge liner with at least two concave regions, whose geometry is selected such that upon the forced collapse of the liner a plurality of cutting jets is formed which jets are convergent or are capable of colliding in the rock strata.

Abstract: The present invention relates to an improved quantum signal transmitter, which has a plurality of quantum output channels having at least one optical source and at least one optical splitter acting on the output of said at least one source.

Abstract: A phased array antenna system with two dimensional scanning includes a two dimensional array A of antenna elements A1,1 to A12,12 arranged in lines; each line is associated with a respective first rank corporate feed network 161 to 1612 having outputs 171,1 to 1712,12 connected to respective antenna elements A1,1 to A12,12 and inputs for variable relative phase input signals. These corporate feed networks each have first and second inputs A1/B1 to A12/B12 connected respectively to outputs 171 CD/1712CD to 171EF/1712EF of different second rank corporate feed networks 16CD and 16EF. The corporate feed networks 161 to 16EF convert input signals of variable relative phase into relatively greater numbers of output signals for a phased array.

Abstract: Liquid crystal compounds of Formula (I) for use in liquid crystal devices contains a dioxatetralin unit within the mesogenic liquid crystal core. The dioxatetralin unit may be located at any position within the mesogenic core of the liquid crystal compound, either at the terminus of the liquid crystal core or alternatively substantially in the middle of the liquid crystal core. The compounds of the invention exhibit fast switching and may be used in liquid crystal mixtures for particular use in imaging or display media, such as monitors or televisions.

Abstract: A vehicle arresting device comprises a net intended to be laid flat on the ground in the path of an oncoming vehicle to be arrested. Two rows of barbed spikes are attached to the net along its leading edge. When a vehicle runs over the device the spikes lodge in its front tires and the net is caused to wrap around the front wheels, eventually being pulled tight under the vehicle so that the tension in the net prevents further rotation of the wheels and the vehicle is brought to a stop. The net is manufactured such that in its deployed condition it has sufficient lateral stretch to allow it to become fully wrapped around the front wheels before the tension builds up to a level at which there might otherwise be a risk of the spikes being pulled from the tires.

Abstract: A method of key distribution from a first entity to a second entity including the first entity communicating with a moveable key device so as to share a secret data with said moveable key device, relocating said moveable key device to a location having a quantum link with said second entity, transmitting a quantum signal from said moveable key device to said second entity on said quantum link, the quantum signal being based on said secret data; and said first entity and said second entity undertaking key agreement based on the quantum signal received by the second entity. Such a method allows the principles of quantum key distribution to be applied even in the absence of a suitable quantum communications link between the first and second entities.