Abstract: A continuous wave laser device (40) comprises a convoluted path or fiber (43) of Raman laser material that has been micromachined on to a substrate, the laser material fiber being covered by protective cladding (30). A 1 cm diameter substrate can have tens of meters of fiber fabricated on it and with a suitable choice for the laser material, e.g. Diamond, can output tens of hundreds of Watts of laser power. One possible use envisaged is as multicolor laser diodes, for example for projection television systems.

Abstract: This invention relates to the field of oil wells and in particular to the explosive and other devices that are used to perforate oil well casings and hydrocarbon bearing rocks in order to create channels through which oil and gas can flow into the well bore. Existing oil well perforators are either termed “big hole” perforators which are designed to produce large holes in the oil well casing only or “deep hole” perforators which are designed to perforate the casing of the well into the surrounding rocks. This invention proposes a novel “dual action” perforator capable of substantially performing the same functions as both deep hole and big hole perforators.

Abstract: A bistable nematic liquid crystal device cell is provided with a surface alignment grating on at least one cell wall and a surface treatment on the other wall. Such treatment may be a homeotropic alignment or a planar alignment with or without an alignment direction, and zero or a non zero pretilt. The surface profile on the monograting is asymmetric with its groove height to width selected to give approximately equal energy within the nematic material in its two allowed alignment arrangements. The monograting may be formed by a photolithographic process or by embossing of a plastics material. The cell is switched by dc pulses coupling to a flexoelectric coefficient in the material, or by use of a two frequency addressing scheme and a suitable two frequency material. Polarisers either side of the cell distinguish between the two switched states. The cell walls may be rigid or flexible, and are coated with electrode structures, e.g.

Abstract: A method of generating force between a structure and an additional member, particularly for reinforcing an existing structure so that an additional member can share existing load. Pre-cooled or pre-heated shims of shape memory alloy (SMA) are inserted between the additional member and the existing structure, or between different sub-units of the additional member, or between the additional member and shoes fixed for this purpose to the existing structure. On subsequent warming or cooling the SMA shims expand to apply compressive forces to the portions of the structure, additional member or shoe(s) with which they are in contact on their opposite sides. Further compressive, tensile, flexural or torsional forces will be developed within other parts of the structure and additional member as a result of the shim expansion depending on the particular arrangement.

Abstract: An electro-optic device such as a smectic liquid crystal cell 1 with an active semiconductor backplane 3 is mounted on a hybrid substrate 2, for example of alumina or silica. Other active or passive electronic or optical components may also be mounted on the substrate, and interconnected by conductive tracks, for example by wire bonding 17, and the substrate itself may be mounted on a printed circuit board. The substrate may comprise a heat sink. The arrangement facilitates the safe connection of the liquid crystal cell and good optical alignment thereof.

Abstract: A multi-layer semiconductor diode having a layer of wide bandgap material located between the active layer and a first contact zone, where the active layer and additional wide bandgap layer are of one dopant type, and the first contact zone is of the opposite dopant type. A specific embodiment of the invention comprises a stack formed from a first contact zone (4) of p-type material, a lightly doped p-type active layer (2), an additional p layer (20) and a second contact zone (6) of n-type material. The diode may be used as an infrared detector or a negative luminescent source.

Abstract: A photodetector circuit incorporates an avalanche photodiode (APD) 300 produced by epitaxy on a CMOS substrate 302 with implanted n-well 304 and p-well 306. The n-well 304 has an implanted p+ guard ring 310 delimiting the APD 300. Within the guard ring 310 is an implanted n+ APD layer 312 upon which is deposited an epitaxial p+ APD layer 314, these layers forming the APD 300. The APD may be incorporated in an amplifier circuit 50 providing feedback to maintain constant bias voltage, and may include an SiGe absorption region to provide extended long wavelength response or lower avalanche voltage. Non-avalanche photodiodes may also be used.

Abstract: A method for compensation for object motion during a scan, especially an magnetic resonance imaging (MRI) scan is provided. The method involves taking a first data set corresponding to a first focussed image and adding a number of data points to form a slightly higher resolution image. Possible motions can then be modelled on the added data points and the effect on the focussing of the slightly higher resolution image determined using appropriate focus criteria.

Abstract: An infrared light emitting diode arrangement comprising an infrared light emitting diode which emits positive luminescence when forward biased and emits negative luminescence when reverse biased. The diode is driven by an alternating forward and reverse bias input so that the difference in output power between the positive luminescence and the negative luminescence of the light emitting diode is stabilised with respect to temperature. The infrared light emitting diode arrangement has particular application as a source in gas sensors and reduces or eliminates temperature control requirements for infrared light emitting diode sources.

Abstract: A method of micro-machining comprising providing a primary region of at least a first material which contacts a second material at at least one end portion thereof, the method comprising providing an infill material on to the second material, patterning and etching said infill material to form a hole through the infill material to the second material, depositing the first material on to said infill material so that the at least one portion of the first material contacts the second material through the hole. The method can be used to provide a track bridging suspended portions of micro-machined structures. Also a method of narrowing and sealing top portions of channels cut into a wafer is disclosed.

Abstract: An optical waveguide with at least a guiding lamina (10) of optical material bonded by direct interfacial bonding to a superstructure lamina (20) of optical material, in which regions of the guiding lamina have modified optical properties so as to define a light guiding path along the guiding lamina. In a particular example, a periodically poled LiNbO3 planar waveguide is buried in LiTaO3 by direct interfacial bonding and precision polishing techniques and used in an optical frequency doubling system.

Abstract: A method and apparatus for processing of a signal in which a variation in phase between a transmitted and reflected pulse is modeled, as is the amplitude of the pulse. The modeled phase and amplitude are used to smooth the data by reducing phase noise present on the signal thereby enhancing the signal to noise ratio.

Abstract: A light emitting device for generating at least one beam of output radiation from an input current of electrons comprises at least two p-n junction devices for converting the input current of electrons into photons, wherein the p-n junction devices are electrically connected in series such that the input impedance of the light emitting device is substantially equal to the sum of the individual impedance of the p-n junction devices. Hence the quantum efficiency of the light emitting device is substantially equal to the sum of the individual quantum efficiencies of the p-n junction devices. In a preferred embodiment, the light emitting device comprises a plurality of p-n junction devices connected in series such that the input impedance of the light emitting device is equal to 50 &OHgr; without the need for additional circuitry or impedance matching elements.

Abstract: A pressure indicator and a corresponding method are disclosed, the pressure indicator comprising a display diaphragm, optionally transparent, and an indicator diaphragm coupled to and in fluid communication with the display diaphragm. In use, pressure is applied to the diaphragms, which may be amplified, whereby a change in the pressure applied causes relative movement between the diaphragms which is observable either on the outer surface of the display diaphragm or through the display diaphragm. The diaphragms may form a compartment preferably containing a liquid or gel. The indicator diaphragm may bear a recognizable configuration or pattern which can be colored and may comprise a symbol or graphic projecting from its surface. The configuration or pattern may comprise at least two components, each component corresponding to a different pressure. Also disclosed is an inflatable device, especially a football or a tire, comprising such a pressure indicator.

Abstract: A method of providing a microprojection (180) on the surface of a first material, the microprojection having a base portion adjacent the first material and a remote, or a tip portion, and a duct (182) at least in a region of the tip portion and the method comprising micro-machining the first material to provide the micro-projection duct. Various uses of the microprojection are also disclosed including light guides and cuvettes from micro-analytical systems, microneedles for transdermal fluid delivery or the like.

Abstract: Relates to constructions of a backplane which comprises an array of addressable active elements 52 on a semiconductor substrate 51 for selectively energizing respective first electrodes 65 of the array, for example in a liquid crystal matrix cell. To reduce photo-induced degradation of images produced thereby (a) at least part of the region beneath a first electrode is adapted to act as a capacitor, for example a depletion layer 66 acting as a reverse biased diode, and/or (b) substantially the whole of each active element is covered by a metallic conductor (59, 60—coupled to row and column conductors). In a variant of (b) the array of active elements may covered by an insulating layer, and each active element is connected to a metal electrode on the insulating layer, the array of said metal electrodes thus formed covering more than 65% of the area of said array.

Abstract: The invention provides a Hall effect magnetic field sensor (10, 50) including carrier excluding or extracting means (36, 66) for reducing an intrinsic contribution to carrier concentration in the active region (14e, 53c) to provide for the sensor to be operative in an extrinsic saturated regime. This provides an advantage that magnetic field measurement sensitivity of the sensor (10, 50) can be made substantially insensitive to sensor temperature thereby improving measurement accuracy.

Abstract: A system for the humidification of polymer electrolyte membrane fuel cells, the system comprising a first layer and a second layer; wherein the first layer comprises a porous material (11) substantially coincident with a first surface of a polymer electrolyte membrane fuel cell (10); wherein the second layer comprises a non-absorbent material (12) substantially coincident with the first layer; and wherein perforations in the second layer allow air to flow through the first and second layers to a cathode (17) of the polymer electrolyte fuel cell.

Abstract: An apparatus for producing a digital depiction of a signal (10) which is adaptive to the signal itself. A constant rate sampling means, such as an analogue to digital converter (2), samples the signal (10) at a constant rate and produces a first digital depiction (12) of a signal. A transformation means (14) is responsive to the first digital depiction (12) and produces a second digital depiction based on the evolution of the signal. The transformation means may be capable of determining when a predetermined threshold level has been crossed and measuring the time interval between predetermined threshold level crossings. The transformation means (14) may include a logic arrangement and a timer counter and is run from a clock signal (16) from the same clock (6) as drives the sampling means. A method of adapting a conventional ADC (2) to adaptively sample the signal (10) by adding a transformation means (14) run off the same clock (6) as the ADC (2) is also provided.

Abstract: A method of recognizing a radar target comprises producing a sequence of Doppler spectra of radar returns form a scene and producing therefrom a sequence of Doppler feature vectors for a target in the scene. Hidden Markov modelling (HMM) is then used to identify the sequence of Doppler feature vectors as indicating a member of a particular class of targets. HMM is used to identify the sequence of Doppler feature vectors by assigning to each feature vector an occurrence probability by selecting a probability distribution or state from a set thereof associated with a class of targets, multiplying the occurrence probabilities together to obtain an overall probability, repeating for other probability distributions in the set to determine a combination of probability distributions giving highest overall probability for that class of target, then repeating for at least one other class of targets and selecting the target class as being that which yields the highest overall occurrence probability.