Abstract: A data communications link uses a multi-power level optical source to encode and transmit data words along a communications channel to a receiver station. A received signal condition monitor senses the level of a pre-determined characteristic and transmits a control signal to a controller which controls the power output of the optical source.

Abstract: An imaging system comprises an image-data collection station (1) having a platform (2) which is rotatable about an azimuthal axis. Several image sensors (3) are mounted on and rotate with the platform (2). A static monitoring station (7) includes a computerized sensor control system (10) for selectably and independently turning the sensors (3) ON and OFF during the rotation of the platform (2). Station (7) additionally monitors the data output from the sensors (3) and delivers a visible output at a VDU (8).

Abstract: Assessing the accuracy with which a round fired from a gun hits an intended target is achieved and alignment of the gun is corrected by monitoring the target with an image sensor which is associated with a computer enabling a frame by frame analysis and comparison of the fired round's trajectory with computer-generated alternative trajectories.

Abstract: A solid state laser has an elongate slab of lasing material having a rectangular cross section with the lower face of the slab contacting a slab mount which is of a high thermal conductivity material. Energy to drive the lasing medium is provided by a flash lamp. Upper and lower faces of the slab are polished to an optically smooth finish so that light is able to propagate in a generally axial direction through the slab. Side faces of the slab are polished and then re-roughened to provide a finish with a surface damage zone comparable in depth to the wavelength of the lasing emission. For a lasing wavelength of one micrometer, the depth of surface damage is in the region of one micrometer.

Abstract: A head tracking system 10 comprises a radiation emitter 18 and a radiation sensor 16 connected to a tracking processor 12. The emitter 18 has an output 46 producing radiation with spectral peak in the range 1000 nm to 1100 nm from a conventional LED 40 with a spectral peak in the range 500 nm to 900 nm in combination with a photoluminescent material 42.

Abstract: A solid state laser has an elongate slab of lasing material having a rectangular cross section with the lower face of the slab contacting a slab mount which is of a high thermal conductivity material. Energy to drive the lasing medium is provided by a flash lamp. Upper and lower faces of the slab are polished to an optically smooth finish so that light is able to propagate in a generally axial direction through the slab. Side faces of the slab are polished and then re-roughened to provide a finish with a surface damage zone comparable in depth to the wavelength of the lasing emission. For a lasing wavelength of one micrometer, the depth of surface damage is in the region of one micrometer.

Abstract: A panoramic display system for use in a vehicle equipped with a plurality of episcopes (22) includes an information gathering sensor and a plurality of displays (24) for the gathered information. Each display (24) is associated with a respective episcope (22) and is operable to display the information gathered from a field of view corresponding to the respective episcope.

Abstract: An optical component having a protective layer provided on a surface thereof, the protective layer preventing the component from being damaged by high velocity impacts from small particles or water droplets. The protective coating comprises a layer of gallium phosphide deposited onto the component surface using plasma assisted chemical vapour deposition (PACVD), an intermediate layer of PACVD boron phosphide, and an outer layer of PACVD diamond-like-carbon.

Abstract: A dual-band optical system 10 preferably for use in the thermal infrared waveband provides initial detection of a target in a first waveband (8-12 .mu.m) having a wide field of view and discriminated target recognition in the second waveband (3-5 .mu.m) at higher magnification and narrow field of view without any field-of-view change mechanism. The system 10 comprises a detector array 11 which is responsive in both wavebands and an optical arrangement 16 with a common objective component 15 for both wavabands. One waveband is transmitted through dichroic beamsplitters 17,18 to the array 11 whereas the other waveband is reflected by the beamsplitters 17,18 and transmitted through a field lens 28 before reaching the array 11. Both wavebands are incident upon a spectrally selective aperture stop 20 providing a large aperture for the low magnification field and a small aperture for the high magnification field.

Abstract: A three field of view change apparatus has a cubic carousel 1 mounted for rotation about a rotation axis 2 which is coincident with a diagonal of the carousel 1. The rotation axis 2 makes an angle of 54.736.degree. with a fixed optical axis 5 so that carousel 1 can be rotated to cause the fixed optical axis 5 to pass through the centres of any two opposed faces of the carousel 1. Optical components 14 are arranged on opposed faces of the carousel 1 and can be swung into alignment with the optical axis by rotating the carousel.

Abstract: An optical system 10 comprises a light source 12 which may be either a point source or collimated and an arrangement 11,22 for directing a beam of light from the source 12 towards a boresighting arrangement 16 associated with an imaging lens 14 for imaging objects in object space 13 onto a detection surface 15. The boresighting arrangement 16 provides a marker on the surface 15 denoting the pointing direction 18 of the system 10 and is arranged so that the marker is of box-like pattern (17A, B 19A, B) closely centred on the pointing direction 18 so as to avoid obscuration of that part of the object image which is coincident with the pointing direction 18.

Abstract: An optical filter comprises a multilayer coating adherent to a substrate, the coating comprising at least four superimposed layer collections. Each layer collection has ordered first, second and third layers of which the first and third layers are made of a first material and are 0.6 quarter wavelengths thick whereas the second layer is made of a second material and is 6.8 quarter wavelengths thick. One of these materials has a high refractive index in the range 1.9 to 2.5 whilst the other of these materials has a low refractive index in the range 1.3 to 1.7. The preferred high index material is zinc sulphide and the preferred low index material is thorium fluoride.The optical filter is generally transmissive except in a number of narrow waveband regions which include respective known laser wavelengths.

Abstract: An integrated optic component comprises a substrate (10) carrying a layer (11) of polymeric material which has an aliphatic or aromatic polymer backbone with bonded sidegroups exhibiting hyperpolarizability. The layer (11) shows a refractive index pattern induced by irradiation with wavelengths within the electronic absorption bands of the sidegroups and within the range of about 230 to 650 nm. The component may be poled so as to be an active component and may be in the form of a ridge guide. Typical sidegroups comprise 4'-amino or 4'-oxy substituted 4-nitrostilbene moieties, or 4'-amino substituted 4-cyanostilbene moieties, or N-substituted 1-(4-aminophenyl)-4-(4-nitrophenyl) buta-1, 3-diene moieties.

Abstract: Infrared transmitting optical components having a wide variety of substrates (e.g. ZnS, ZnSe, Ge, Si, SiO.sub.2) are disclosed all with an optical coating of boron phosphide (BP). The boron phosphide may be a single layer coating or one layer of a multilayer coating in which case it is preferably the penultimate layer. Coated components are provided which are very low in absorption, which are operable at high temperatures with minimal transmission loss, and which are transmitting in two IR wavebands. The boron phosphide layer is deposited by plasma-assisted chemical vapor deposition at a temperature in the range 300.degree.-500.degree. C. preferably using feedstock gases which are hydrogen-fee. Boron phosphide coatings of up to 40 .mu.m in thickness have been achieved.

Abstract: A radiation mast such as a periscope has a head end 10 incorporating a radiation receiver in the form of a top mirror 12, the lower end 11 of the mast being physically separated by a considerable distance from end 10 and being provided with an information station, for example, in the form of viewing optics (E) and/or a video monitor 17. The radiation image formed at the receiver 12 is viewed at the information station in accurate superimposition with a reference pattern which is electronically generated by generator 19 and which is stabilized in space with respect to at least pitch, roll and yaw movements of the vehicle on which the mast is mounted. The pattern is also stabilized with respect to such disturbance factors as are effective on the information relaying means, for example, optics in path B, C, D, whereby the radiation image can be visually referenced to the electronically generated pattern, unwanted relative movements having been eliminated.

Abstract: Optical components (16), particularly germanium components, are provided with a coating on exposed surface (15) within a vacuum chamber (17) by production of a glow discharge plasma containing carbon and another depositable element from feedstock gases which are fed to the chamber (17) via mass-glow rate controllers (9, 10, 11). The mass flow rate of the feedstock gases is maintained substantially constant at predetermined levels during respective time intervals to provide a multilayer coating of predetermined characteristics. Typically the coating has at least one first layer which is amorphous hydrogenated germanium carbide, at least one second layer which is amorphous hydrogenated germanium and at least one third layer which is amorphous hydrogenated carbon, these layers being ordered such that each second layer is bounded on each side by a first layer and the third layer is bounded on one side by a first layer, the other side of the third layer forming the exposed surface of the coating.

Abstract: A submarine periscope system has a mast head 7 with a casing 10 from which protrudes a shaft 16 carrying observation instruments which are protected by a housing 8. A seal arrangement 30 is provided at the interface between the casing 10 and shaft 16 which imposes low friction torque at water pressures within the operational depth range of the periscope system and permits the shaft 16 to rotate for azimuthal movement of the observation instruments. A rotary drive 14 is connected to the shaft 16 for this purpose. The seal arrangement 30 imposes high friction torque at water pressures outside the operational depth range of the periscope system and a water depth pressure valve disables the shaft rotary drive to provide integrity of the seal arrangement outside the operational depth range. The mast head 7 is telescopically extendable by a hoist device 13 and does not penetrate the hull 2 of the submarine 3.

Abstract: Flexible coherent optical glass fiber bundles are manufactured from rigid coherent optical glass fiber bundles by selecting the fiber bonding agent to be an acid-leachable glass having a silica content in the range 8-15% molecular and removing acid-leachable glass from the rigid bundle by immersion of the bundle in a mineral acid leaching solution having a concentration in the range 5-30% by volume.

Abstract: A gunnery training system comprises a conventional armored vehicle having a gun and a fire control system to which is releasably attached portable training equipment (TT), which in operation uses almost all features of the conventional equipment within the vehicle so that a high standard of realism is obtained. The equipment (TT) delivers simulated scenic images with overwritten simulated target images to the visual display of the vehicle, the scenic images being selected by gun orientation signals extracted from the fire control system. Initiation of the laser rangefinder which forms part of the fire control system causes the equipment (TT) to deliver range data on the simulated target so that the fire control system overwrites a corresponding aiming mark on the visual display. When the gun trigger switch is operated the equipment (TT) captures the location of the aiming mark and computes the displacement between that location and the position of the simulated target as a measure of training efficiency.

Abstract: A submarine periscope of the non-hull penetrating type has an extendable hoist (11) secured at one end to the submarine hull (2) and at its other end carries a sensor pod (8). Pod (8) is rotatable by a motor (13) carried by the hoist (11) and is electrically connected to sensory signal output devices (34,35) inside the hull (2) by a flexible cable (24) penetrating hull (2) at a gland (21) to which is fitted a rotatable signal transmission device (19). Cable (24) terminates at slip rings (32) secured to the transmission device (19) inside the hull (2). The transmission device (19) is rotatable by a motor (29) and motors (13,29) are both controlled by a controller (30) arranged to provide for synchronous rotation of pod (8) and device (19).