Abstract: In an earlier Specification there is described and claimed a surveillance arrangement suitable for use in an aircraft wherein a television camera/display combination provides an image of the viewed scene, and infra-red detector means viewing part of the same scene provides brighten-up signals to effect a localized increase in intensity of the displayed image to highlight heat emitting targets in that part of the viewed scene; the resultant display is ultimately made available to the pilot via a HUD screen. This arrangement is not always satisfactory, and the present invention seeks a better solution by arranging for a target-emphasising visual effect to be generated and projected onto the HUD screen quite separately of the view of the scene, whether that view is obtained directly (through the HUD screen) or indirectly (from an image projected onto the HUD screen).

Abstract: A fibre optic terminal (1) for use with a bi-directional optic fibre (6) including an optical receiver (2) positioned in the path of light (8) emitted from an end (5) of the optical fibre to receive the light, and an optical emitter (4) arranged to emit light (7) from a position adjacent the optical receiver onto the end of the optical fibre, the position being in the path of light emitted from the end of the optical fibre so that substantially all of the light emitted from the optical emitter is incident on the end of the optical fibre, and the area from which the optical emitter emits light being small relative to the light receiving area of the optical receiver so that substantially all of the light emitted from the end of the optical fibre is received by the optical receiver.

Abstract: A redundant actuator system in which some of the sub-actuators have a lower force capability than the other sub-actuators. The lower force capability sub-actuators are controlled by a common electrical control circuit while the other sub-actuators are each independently controlled by separate control circuits. A plurality of hydraulic supplies power the sub-actuators, each supply powering one lower force capability sub-actuator, and at least one other sub-actuator.

Abstract: A position measuring system comprising a transmitter (5, 19) mounted on one body and arranged to direct a flashing beam of radiation onto an area sensor (11) which is mounted on the other body and forms part of a receiver arranged to produce an output indicative of the position of impingement of the beam on the sensor from samples of the radiation impinging on the sensor when the beam is on and off, the receiver including a second sensor (31) responsive to the radiation beam whose output synchronizes the operation of the receiver to the flashing beam. The requirement for a physical connection between receiver and transmitter to synchronize the receiver with the flashing beam is thereby avoided.

Abstract: A display unit for a head up display wherein the combiner (9), which serves to reflect light from a display surface (3) towards an observer to provide the observer with an image of the display superimposed on his view through the combiner, comprises first, second and third tuned reflective optical films (13c, 15c, 17c) disposed in such angular relationship with one another and the display surface that narrow waveband light from the display surface reaches the observer after being, successively, reflected at the first film, transmitted through the second film, reflected at the third film, reflected at the second film and transmitted through the third film.

Abstract: A display unit for a head-up display system which includes a periscopic arrangement 21a,b at each side of the exit pupil 19 of an optical projector. This arrangement is effective to direct collimated light to a conventional monocombiner 11, from lateral portions of the display which otherwise would not be received by the observer without head movement. It thereby increases the observer's instantaneous azimuth field of view of the display.

Abstract: According to the present invention a sight unit, for an headgear comprises a mount member adapted to be secured to the headgear, an arm member pivotally connected to the mount member, a collimating sight carried by the arm member, and, a substantially flat display surface a virtual image at infinity of which is to be formed by the collimating sight and in which the arm is pivotal between an operative position at which when the headgear is being worn the sight intercepts the wearer's forward line of sight to the distant scene and a stowed position at which the sight does not intrude into the wearer's field of view to the forward distant scene, and no part of the arm or the sight has a transverse dimension greater than a prescribed human interpupillary distance, wherein the said display surface is secured to the mount member and when the arm is at the operative position the sight defines an optical axis which intercepts the display surface perpendicular thereto.

Abstract: A digitally controlled, presettable, ramp signal generating arrangement comprising digital to analogue converter means (DA) and integrator means (A1, A2) having a first mode in which its output (0) assumes a value representative of the output of the converter means, and a second mode in which its output changes at a rate dependent on the output of the converter means. The arrangement finds especial application in symbol display arrangements.

Abstract: Semiconductor crystals for use, for example, in the manufacture of integrated circuits are required to be inspected for crystal lattice perfection before any subsequent circuit processing. This can be done by X-ray diffraction in which the crystal is curved so that a divergent beam irradiates all points of the crystal surface at the same angle and simultaneously. The difficulty is however, in holding the crystal in the appropriately curved form while at the same time not obstructing the passage of X-rays from the front or back of the crystal and so enable topographs to be obtained by both reflection and transmission. According to the invention, in such a system the crystal is attached to a flat, X-ray transparent plate by pneumatic X-ray transparent means, and the plate is deformed to the required curvature, carrying the crystal with it.

Abstract: A data transmission system including a transmitting station (13 to 15 and T) wherein three-state signals representing data are converted to two-state signals so that the data can be transmitted via a transmission line adapted to transmit only two-state signals such as a fibre optic transmission line.

Abstract: The effects of wind noise signals from fence-mounted transducers are overcome by basing alarm indications on signal components in at least two narrow frequency bands centered on, say, 120 Hz and 240 Hz.

Abstract: A latch mechanism for controlling relative movement of two hinged members about an axis, e.g. a helmet and visor. The mechanism comprises a first part (19) fixed to one hinged member and a second part comprising a first member (25) fixed to the other hinged member (13) and a manually operable second member (27). On application of pressure the second member (27) pivots on the first member (25) against a spring bias (43) to disengage the second member from the first part (19) and allow the second latch part (25, 27) to move angularly with respect to the first latch part (19) under continuing pressure on the second member.

Abstract: A circuit for driving a deflection coil comprising a capacitor (3) in series with the coil (2), a circuit (1) which drives a saw-tooth waveform current through the coil and capacitor, and a switchable resonant circuit (5, 6, 7, 8, 9) which generates across the capacitor a saw-tooth waveform voltage equal and opposite to the voltage drop attributable to a resistive component (4) of the capacitor/coil series circuit, thereby to effect loss correction.

Abstract: A display head for an aircraft head-up display system wherein a display developed by a projector (11) is reflected to the observer in part by a semi-reflective coating (31a) on the side (29a) of the combiner light transmissive body (27) nearer the observer, and in part by a semi-reflective coating (31b) on the side (29b) of the combiner body further from the observer, the two coatings being positioned relative to one another and the projector to provide the observer with an uninterrupted instantaneous field of view of the display.

Abstract: A vehicle display arrangement comprising a head-up display unit (11) and a head-down display unit (13) providing a collimated display which appears to an observer to be a continuation of the head-up unit display. A fully reflective element (29) between the units cooperates with a parallel semi-reflective element (23) in front of the head-down display to shift head-down display information so that there is no gap in the display corresponding to the space (38) between the units.

Abstract: A method of terminating an optical fiber cable wherein an annular deformable member (1) is compressed inwardly onto a cable (7) threaded through it by causing an encircling cincture (3) exhibiting `memory` properties to try to return to a remembered shape and size.

Abstract: A modification of the hot crimp technique described in U.S. application Ser. No. 701,240 filed 30th June 1976. In that case a bundle of fibres was inserted into a glass sleeve and the sleeve and fibres were thrust into a hot conical bore to compress the sleeve and fibres to remove interstitial dead space.In an incidental feature of that technique, the compressed bundle is maintained concentric with the outer sleeve surface, and in fact, with the outer surface of a metal sleeve which may provide the conical bore. This feature is adapted for the present invention in which a single fibre is inserted into a close fitting glass sleeve through a tapered lead-in ferrule, the sleeve and ferrule are thrust through an outer metal sleeve having a conical end so that the glass sleeve and fibre are compressed concentrically. The assembly then provides an accurately concentric single fibre termination pin.

Abstract: A method of terminating an optical fibre cable wherein an annular deformable member is compressed inwardly onto a cable threaded through it by causing an encircing cincture exhibiting `memory` properties to try to return to a remembered shape and size. The annular member includes a plurality of portions which are held apart by spacer material to define a passageway through which the cable is threaded, the spacer material being subsequently caused to deform e.g. by heating, so that under the force exerted by the cincture said portions are urged inwardly and grip the cable.

Abstract: A display unit for a head up display wherein the combiner (11), which serves to reflect light from a display surface (14) towards an observer to provide the observer with an image of the display superimposed on his view through the combiner, comprises first and second tuned reflective coatings (25c and 27c) disposed in such angular relationship with one another and the display surface that narrow waveband light from the display surface reaches the observer after being successively transmitted through the first coating, reflected at the second coating, reflected at the first coating and transmitted through the second coating.

Abstract: A method of displaying a symbol on a display area which is effectively a regular array of display elements wherein the symbol is defined by a multiplicity of equally spaced points on the display area and each point is represented by a group of display elements whose relative brightnesses are set so as to create a subjective impression of that point at its required position. The technique avoids the so-called "staircase effect" on symbols. Apparatus for generating brightness control signals for carrying out the method is also disclosed.