Abstract: A liquid crystal device comprises backlighting means to provide illumination from the rear for a liquid crystal panel. The backlighting means has a layer of light-transmitting material formed with a prismatic region at one edge and a plurality of light sources of differing chromatic output, located adjacent the prismatic region.

Abstract: An electromagnetic article, such as a responder tag for detection by an electronic article surveillance (EAS) system, is fabricated by forming a deposit of a relatively low coercivity high permeability magnetic material on a substrate 22 under the influence of an applied magnetic field so as to provide the deposit with easy and hard axes of magnetization. During deposition the substrate is subjected to a mechanical tension 32 so as to provide the deposit with an inherent benign strain substantially aligned with one of the axes of magnetization. The inherent benign strain is arranged to dominate any detrimental strain to which the responder tag may be subjected during use, enabling detection by the EAS system to be maintained.

Abstract: A thermal imaging device includes an array of pyroelectric infra-red detector pixels. An array of pillars carries electrical signals between each detector pixel and a respective signal processing circuit formed on a semiconducting substrate. Each circuit is connected to an individual display device carried by the substrate.

Abstract: A discharge tube arrangement includes a discharge tube of a light-transmissive dielectric material and containing a fill. An excitation device for exciting surface waves in the discharge tube comprises an r.f. power generator and a launcher. The launcher is formed as an inner tube, an outer tube coaxial with the inner tube, and first and second end walls, at least one of the first and second end walls having an aperture for receiving the discharge tube. Means are provided inside the launcher for coupling r.f. power to the inner tube. A body of dielectric material extends from the inner tube to the outer tube, thereby to hold the tubes in fixed relative positions, the body encasing the coupling means.

Abstract: A fluorescent lamp for use in aquaria, the luminescent layer in said lamp comprising a mixture of red, green and blue phosphors, the red phosphor emitting predominantly in the spectral region of from 610 nm to 620 nm, the green phosphor emitting predominantly in the spectral region of from 540 nm to 545 nm and the blue phosphor having a peak emission wavelength between 430 nm and 480 nm with the half peak width not exceeding 80 nm, said red, green and blue phosphors being blended to form said mixture in such proportions that the color co-ordinates of the lamp employing said mixture on the CIE chromaticity diagram differ from the point x equals 0.300 and y equals 0.232 in any direction by no more than 10 standard deviations of color matching (SDCM). Aquaria employing such lamps are also disclosed and claimed.

Abstract: An apparatus for measuring the frequency of an input signal is described. The apparatus uses a quadrature sampling system to obtain values of the instantaneous phase of the signals at a succession of time intervals, the values being converted into cumulative phase values. An estimate of the frequency is obtained by determining the gradient of the straight line which would best pass through a plot of the values of cumulative phase against time.

Abstract: A method is provided for addressing a matrix-array type liquid crystal cell with a ferroelectric liquid crystal layer having a plurality of pixels defined by areas of overlap between members of a first set of electrodes on one side of the liquid crystal layer and members of a second set of electrodes on the other side of the liquid crystal layer, each of the pixels having a first and a second optically distinguishable state and a response time for switching between the two states which depends on the potential difference across the liquid crystal layer. The method includes the step of applying a switching pixel waveform to a selected pixel to switch it between the two states. The switching pixel waveform is charge-balanced and comprises a first pulse having a sufficient pulse width and pulse height magnitude to switch the selected pixel and a second pulse contributing to charge-balancing.

Abstract: A starter circuit for a discharge lamp includes a current control circuit which initially has a low impedance so as to produce an initial cathode heating current for the lamp. The current control circuit is switched into a high impedance condition by means of a control voltage applied to its gate thereby causing a high voltage striking pulse to be applied across the lamp. A field effect transistor is effective to modify the control voltage to the gate such that the starting circuit is effective to produce a succession of starting pulses across the lamp during each half cycle of a rectified AC supply.

Abstract: A fluid meter comprises at least three sensors each having an output dependent on a respective characteristic of the fluid to be monitored, circuitry to combine the outputs of two of the sensors to provide a measurement of mass flowrate of the fluid, and to combine the outputs of the three sensors to provide an error signal which can be used to recalibrate the measurement.

Abstract: An electrically resistive track suitable for use as a heating element consists of a thick film including a base metal constituent and a glass constituent. The thick film has in the temperature range of from 20.degree. C. to 600.degree. C. a temperature coefficient of resistance (TCR) less than 0.0050 per degree C. Suitable metal constituents include tungsten, molybdenum, a mixture of nickel and tungsten and a mixture of nickel and chromium.

Abstract: A required visual signal for direct observation is produced from a first source of light in the presence of a second source of light, such as ambient light. Light is transmitted from the first source to a defined surface or defined region distant from the first source. A means for modulating light is operated between at least a first mode and a second mode. This operation is synchronized with a varying of the intensity of at least one of the sources of light at or above a given frequency equal to or greater than the critical fusion frequency for the size and luminance of the required visual signal. When the modulating means is in the first mode, this allows the required visual signal to be directly observed on the defined surface or in the defined region. When the modulating means is in the second mode, this allows the effect produced by any light from the second source incident on the defined surface or in the defined region to be reduced.

Abstract: A scanned 2- or 3-D modulated light pattern originating from a light source and represented by a matrix of pixels is projected onto a defined surface or into a defined region distant from the light source. A plurality of means for modulating light one operated between at least a first mode and a second mode. This operation is synchronized with the scanning of the matrix of pixels so that:(a) respective modulating means is in the first mode when its associated plurality of pixels are being scanned; and (b) a respective plurality of pixels are not being scanned when its associated modulating means is in the second mode. When a modulating means is in the first mode, it allows light to be distributed from the defined surface or the defined region. When a modulating means is in the second mode, it allows the effect produced by any light incident on the desired surface or in the defined region to be reduced.

Abstract: A pyroelectric film has a pattern of interconnected electrodes formed on one major surface, and a pattern of discrete electrodes and electrically conductive patches formed on the other major surface. The film 21 is supported by pillars connected to the patches, the pillars also producing a path for electrical signals between the patches and a signal processing means. Each discrete electrode is connected to a respective patch by a respective strip of electrically conductive material.

Abstract: In a discharge arc lamp, an arc tube comprises an arc tube body and a main electrode at each end inside of the arc tube body, between which in the operating condition of the lamp a discharge takes place. At each end of the arc tube is an end closure comprising an end plug joined to respective each end and a cap member, the end plug and the cap member having facing surfaces. A seal provided by sealing means to seal the cap member to the end plug includes an annular seal portion between the facing surfaces of the end plug and the cap member. One or both of the facing surfaces is so shaped that the annular seal portion has a predetermined and uniform thickness t.

Abstract: A heating unit includes a heatable surface. At least a region of the heatable surface is coated or otherwise provided with a layer incorporating a thermochromic material in sufficient quantity to influence the perceived color of the layer. The thermochromic material exhibits an absorption edge wavelength which changes reversibly with temperature in the range of from 20.degree. C. to at least 400.degree. C. The absorption edge wavelength is at least 540 nm at 20.degree. C. and progressively increases to at most 700 nm at 400.degree. C. Such a heating unit is able to provide a visual indication of whether or not the heatable surface is still hot once the power has been switched off. Useful thermochromic materials include Cd(S.sub.1-x Se.sub.x) and (Zn.sub.1-y Mn.sub.y)O.

Abstract: Langmuir Blodgett films are provided having second order molecular hyperpolarizability of at least 30.10.sup.-50 C.sup.3 m.sup.3 J.sup.-2. combined with chemical stability and a melting point of over 70.degree..They also have desirable pyroelectric properties shown by a static pyroelectric coefficient of at least 0.0039 nCcm.sup.2 k.sup.-1. The films comprise compounds of the following formula: ##STR1## wherein M is ruthenium, iron or cobalt; R.sup.1 is cyclopentadienyl, methylcyclopentadienyl, pentamethylcyclopentadienyl or indenyl;A.sup.1 is (R.sup.2).sub.3 Z or carbonyl;Q.sup.2 is (R.sup.2).sub.3 Z or carbonyl;Z is phosphorus or arsenic;R.sup.2 is an aryl of alkyl radical;A is ##STR2## Y is a straight chain alkyl or alkoxy radical comprising from 3 to 17 carbon atoms, or, when A is ##STR3## N(R.sup.3).sub.2 ; R.sup.3 is a lower alkyl radical comprising up to 5 carbon atoms; andX is PF.sub.6 or BF.sub.4.

Abstract: An electroluminescent device comprises a film containing a phosphor. Means for causing movement of electrons in the film comprising a first layer on one side of the film and a second layer on the other side of the film are provided. The film includes a first material which is also present in the first layer. It has been noted that such a device has enhanced luminescence as compared to a conventional electroluminescent device.

Abstract: A thermal imaging device comprises a layer 11 of pyroelectric material, an array of interconnected electrodes 13, and an array of discrete electrodes 15 supported from a substrate 27 by pillars 23 of thermally insulating material. Heaters 17 and associated control electrodes 19 are also provided to reduce the temperature difference between the discrete electrodes 15 and the pillars 23 and substrate 27. Control circuits 25 are provided to control energisation of the heaters 17.In a preferred embodiment the heaters may be provided on the substrate 27 for heating the discrete electrodes 13, the control current to the heaters providing an indication of the temperature of the source of radiation.

Abstract: An optical image rotator assembly has both a rotational axis and an optical axis. Provision is made for adjusting the alignment of the optical axis, both angularly and translationally, in relation to the rotational axis.

Abstract: An electrical connector for making a connection to a thick film track comprises a plurality of conductive fibres braided together, each of the fibres having a diameter so as to provide sufficient stiffness to the connector and to permit adhesion of the connector to a thick film track.