Abstract: A multi-access fiber optic communication system in which each terminal of the system is directly connected with n other terminals of the system via point-to-point transmitting and receiving links and each terminal of the system includes regenerating means whereby a signal received by that terminal is re-transmitted to the other n terminals. The signals are pulse signals and the regenerating means are arranged to re-transmit a received pulse in response to the leading edge of a received pulse.

Abstract: A method and apparatus for testing a ferruled termination of a fibre optic cable by illuminating the active optical area of the cable at the end of the cable remote from the termination and successively measuring through a series of apertures of different area aligned with the ferrule the light energy output from said termination. The apertures may be provided by a series of apertures in a plate or may be provided by a shutter having an opening which may be discretely set to each of the apertures.

Abstract: Electric signals in two narrow frequency bands, centered on thirty-three and one hundred Hertz, arising from ground or airborne vibrations incident on one or more geophones are processed to give an alarm when signal components in the two bands exhibiting a rapid rise to greater than a predetermined amplitude level, characteristic of human footsteps within a protected area, occur at more than a predetermined repetition rate.

Abstract: This invention is concerned with generating line symbols (e.g. straight lines, circles) on cathode ray tube displays with TV-type scans. A tube 10 has the normal line and frame deflection waveform generators 12 and 13 and a normal video amplifier 15. A symbol generator 20, 20', 20", etc. is provided for each symbol; the generators may be controlled by a computer 21 which defines the parameters of the symbol (e.g. slope and position of a straight line). Each symbol generator contains two waveform generators--line and frame frequency waveform generators synchronised by the line and frame synch pulses LSV and FSV--and a comparator which produces output pulses when the voltages from the two generators are equal. These pulses are fed to the video amplifier 15. The waveforms generated by the two generators are chosen to give the desired symbols; e.g. sawtooths for straight lines, parabolic waveforms for ellipses. The output pulses have substantially vertical leading and trailing edges.

Abstract: An aircraft head-up display head of the kind incorporating an image combiner through which an observer can view a distant scene, and from which optical images developed and projected by an optical projector are reflected to the observer, wherein the combiner is supported from a light obstructive member, e.g. the projector housing, which intrudes within the observer's field of view of the distant scene, but is sufficiently narrow not to obstruct the observer's field of view.

Abstract: A display arrangement having a plurality of data display areas in which data is entered via manual controls is provided with a visual indication of the display element or area addressed. A first control knob selects the area addressed and a second control knob allows alteration of the data at the addressed area. The invention is primarily intended for "one handed" operation in which the manual controls are out of the line of sight of the operator.

Abstract: A head for sensing fluid flow pressure of the kind comprising a swivelling pitot tube wherein the pitot tube is mounted on a hinge joint through which fluid pressure at the pitot tube and the angular position of the pitot tube are transmitted without the use of dynamic seals. The fluid pressure is transmitted via a passageway extending by way of the hollow pivot pin on one member of the hinge joint to which the pitot tube is fixed, a hollow shaft in the other hinge joint member and a flexible tubular connection between the pivot pin and shaft, the shaft being coupled to the pivot pin so as to rotate therewith and reduce relative rotation between the ends of the flexible connection. The angular position of the shaft indicates the angular position of the pitot tube. The head finds especial application in helicopter airspeed measuring apparatus.

Abstract: In the manufacture of a monolithic light-emitting diode array, electrical isolation between the n-type regions of portions of the array, for example the columns of a matrix array, is effected by mechanically cutting channels between the portions, through the n-type region and the common electrode. This method of forming the isolation channels makes it possible to produce much narrower channels than can be achieved by chemical etching, thus providing a high resolution array.

Abstract: A head-up display optical projector using a Petzval type collimating optical system wherein a secondary image is injected through an optically flat peripheral surface of a lens included in the Petzval lens group closer to the main image display surface of the projector, the lens incorporating an interior flat dichroic film for combining the main and secondary images.

Abstract: A missile is guided onto a target by means of a laser beam, so that the missile can determine and correct its displacement from the boresight of the laser beam. This leads to greater accuracy of guidance, and avoids the need for very narrow beams which could be lost by the missile.

Abstract: An aircraft weapon system including a component mounted on a wing of an aircraft and a radiation source and sensor arrangement for measuring changes in the alignment of the component with respect to a reference axis fixed with respect to the main body of the aircraft.

Abstract: A missile guidance system uses a television system for viewing targets, and is primarily intended for sea craft. Sectors of the horizon view are displayed one above the other on a television display. Individual sectors can be magnified as required.

Abstract: The invention provides an image motion compensation arrangement for enabling stabilization of the line of sight of a scanned imaging system mounted on a vehicle. In one example the scanned imaging system is a television camera assembly which is resiliently mounted and carries a plane mirror on to which is directed, via an auto-collimating lens, light from a light emitting diode. Light reflected by the plane mirror passes back through the auto-collimating lens to be received by a detector having quadrant receiving surfaces which resolve the complex motion of the camera assembly during movement of the vehicle into two orthogonal components defining the angular error caused by the motion in the sight line of the camera. The two orthogonal components are utilized to provide a pair of electrical signals utilizable to correct for the image motion resulting from the rotation of the sight line.

Abstract: The invention concerns charge coupled devices and the problems of dark current effects. In an arrangement including a charge coupled device utilized as a storage element for data a second charge coupled device is provided. Data is applied to the first device during one half of the storage period, the content of the first device transferred to the second during the second half of the storage period and at the end of the storage period the stored contents of both devices are subtractively combined. In one particular case the arrangement is a CCD television camera of the field transfer type where the normally provided one charge coupled device is replaced by first and second charge coupled devices and the optical image from the optical section of the camera is directed first to one device and then to the second device and the contents of the two devices are exchanges at the end of a storage period.

Abstract: A field sequential television camera is provided in which a disc having a plurality of differently colored segmental filters is rotated in front of an image isocon camera tube. Normally six segmental filters are provided presenting sequentially, red, green and blue in order. The image section of the camera tube is arranged to be gated so that an electron image reaches the target only during a fraction of each sequential color field sufficient to permit operation of the target above the knee of its transfer characteristic.

Abstract: The invention provides a surveillance arrangement, and in particular an airborne surveillance arrangement, in which a television display of a scene is brightened up, by means of infra-red detectors, to emphasize heat emitting targets.In one example of airborne surveillance system, a linear array of infra-red detectors is arranged to view part of a scene viewed by a television camera, with the same horizontal field of view at a desired target range. In front of the array of detectors a light chopper is provided so that the output of each detector is a modulated carrier. The output of each detector is applied to a store, via individual impedance transformers, narrow bandpass filters and demodulators. Between each demodulator and the store, individual sharp out-off low pass filters and threshold detectors may be provided to provide a degree of discrimination against spurious responses.

Abstract: An improved fibre-optic cable termination which substantially reduces light losses and also facilitates cable termination in the field as opposed to the factory.According to this method the fibres are compressed by pushing the bundle, preferably sheathed in a thin glass ferrule, into a heated tool having a tapered hole. A protective metal coupling may be incorporated by heating a metal sheath with a tapered bore and pushing the glass sheathed bundle into the metal sheath. The metal sheath may then constitute a pin of a pin and socket optical coupling.In all cases the temperature and pressure are adjusted so that the individual fibres are squeezed into approximately hexagonal form so as to eliminate the interstices to a substantial extent. The temperature and pressure are, however, limited to prevent any substantial fusion and coalescing of fibres and consequent loss of the optical barrier between them.

Abstract: A helmet sight system for use in an aircraft in which the angular displacement of the helmet in the reference frame of the aircraft is measured by measurement of the angular displacement of a set of three non-colinear radiation sources, fixed with respect to the helmet, whose angular positions are sensed by a sensor which is fixed with respect to the coordinate reference frame of the aircraft. The radiation sources may be light emitting diodes and the sensor may comprise an aperture having two mutually inclined rectilinear slits and an array of light sensitive charge coupled devices.

Abstract: The invention provides a scanning mirror system with line of sight stabilization. In one embodiment a mirror and a balance member are mounted to rotate and the mirror is coupled by means of gear teeth to the balance member so that the inertia of the balance member tends to compensate for the inertia of the mirror. The mirror is arranged to be rotated by a drive motor and a gyro, driven at twice the mirror angle, is arranged to detect rotational movement of the mirror. The gyro is connected in a feedback control system with the drive motor in order to tend to maintain the mirror stationary when the mirror is not being driven through a desired angle by the drive motor.

Abstract: A television camera contains its electrode sub-assemblies mounted on printed circuit boards which extend radially from the central axis of the camera tube. The camera is provided with a cast spherical housing having a window located on the axis of the camera tube.