Abstract: A camera producing colour video outputs may employ an image intensifier 5 and a monochrome CCD sensor 3. The scene is exposed through filters F3, F4 which may each contain stripes of subtractive primary colours alternating with clear regions. The video is decoded using waveforms derived from a memory which records the output of the sensor when imaged on, for example, primary colours such as red and blue, producing trains of pulses which identify the spatial regions of each line corresponding to the spatial areas of the pattern on the sensor produced by the colour filters F3, F4, in order that actual scenes can be decoded using the stored waveforms, for example using sample and hold devices. A colour interference signal is generated in matrix addition circuitry 10 to produce a luminance signal which has stripe visibility removed from it, permitting high resolution video signals to be obtained.

Abstract: An underwater vehicle having a negative buoyancy and thrust units by which it can hover is described. Slow speed maneuverability while hovering is achieved by moving the position of a mass fore and aft and/or side to side such as to cause the vehicle to pitch or roll and thereby vector the otherwise vertical thrust such that the vehicle is propelled in the direction in which the mass has moved.

Abstract: According to a first aspect of the invention, a power control switch comprises two solid state switching elements (14, 15) in parallel, the second switching element (15) having a higher resistance but faster turn-off time than the first element. In operation the switch is pulse width modulated and the first element is switched off after the second element to establish a guard period, the duration of which is controlled in dependence upon the duty cycle to provide efficient switching. According to a second aspect of the invention a power control switch comprises a switching element (14 or 15) controlled by a field programmable gate array (5) which is preferably programmed by an erasable programmable read only memory (EPROM), thereby providing a reconfigurable control means.

Abstract: A display arrangement comprises an image intensifier tube or some other device which provides a representation of a viewed scene at an input. A supertwist LCD and associated polarizers and are located between the input and a viewer. A ferroelectric liquid crystal shutter is located between the LCD and second polarizer and is controlled to produce symbology. By switching the shutter the polarization of the incident radiation is switched between two states differing by 90.degree.. This causes the LCD to operate in two states. In one state the viewed scene is transmitted through the LCD and in the other state it is absorbed and any symbology on the LCD is contrasted with a dark absorbing background. The shutter is switched sufficiently quickly that the viewer perceives the symbology overlaid on the viewed scene. In another arrangement, lens means having focusing properties which are dependent on the incident polarization is included to allow switching between different display modes.

Abstract: A submarine propulsion system for a submersible vehicle has two motors mounted on respective support arms able to rotate about two axes relative to the submersible vehicle. Rotation of each arm about its first axis moves its respective motor out of a storage recess, in which it is stored when not in use, into an operating position and rotation of the same arm about the other axis moves its respective motor between two operating positions in which it generates vertical and horizontal thrust respectively.

Abstract: An optical device for generating a modulated, phase controlled RF carrier by combining a modulated optical carrier signal having a first frequency with an unmodulated optical reference signal having a second frequency. The modulated and unmodulated signals are polarized on orthogonal axes and are transmitted in a single optical waveguide. Modulation of the optical carrier is performed, for example, by means of an integrated optical device which modulates only one polarization direction.

Abstract: In an antenna array consisting of a plurality of antennas, an antenna may behave as if its transmitted radiation emanates from a position, phase center, disposed away from the actual location. Probe antennas are used with a processor to locate the phase center of respective antennas at a selected frequency of transmission and to adjust the phase center to a desired location, thereby calibrating the antenna array for the selected frequency.