Abstract: A clamp mechanism (19) for clamping the edge (17) of a printed circuit board (11) between the side walls (91a, 91b) of a slot in a wall (93) of an enclosure for housing the board in parallel spaced relationship with other boards. The mechanism (19) comprises an elongated element (21) of resilient material having corrugations (23) whose crests are at regularly spaced positions along its length. An actuator (25) coupled with the elongated element for relative longitudinal motion therewith is provided with riser elements (31b) spaced like the corrugations and positioned so as to move on such relative motion into engagement with the crests to effect the required clamping action. The riser elements (31b) are in the form of rollers (31b) to minimize functional resistance to operation. A spigot arrangement (89, 95) on a lever 75 for operates the mechanism which provides positive locking of the board (11) when clamped.

Abstract: A helmet system comprising a helmet (11), a vizor (13) pivotally mounted on the helmet, and mounted on the vizor (13), an electro-optical system, e.g. a night vision goggle, including an eyepiece (33) positioned between a transparent part (19) of the vizor and the user's eye so as to provide the user with a view of a scene forward of the user through the eyepiece, the eyepiece also serving as a combiner to provide the user with a virtual image of a display produced by the electro-optical system superimposed on his view of the forward scene through the eyepiece.

Abstract: A helmet supported optical system which provides an eye of a wearer (11 or 49) of a helmet (7 or 35) with a direct view of the scene forward of the wearer (11 or 49) on which is superimposed collimated optical imagery. The system comprises: an eyepiece (1 or 47a, 47b); means (5 or 37a, 37b, 39a, 39b, 41a, 41b, 43a, 43b) operable to develop a bright data representation at a plane (31or 44a, 44b) substantially congruent with the principal focal plane of an element (21 or 46a, 46b) of the eyepiece (1 or 47a, 47b); and, disposed between the means (5 or 37a, 37b, 39a, 39b, 41a, 41b, 43a, 43b) operable and the eyepiece (1or 47a, 47b), a body (3 or 45a, 45b) of light refractive material.

Abstract: A helmet display system including a display arrangement (5) located between a helmet body (1) and a helmet visor (3). The display arrangement (5) includes right and left collimating eyepieces (7,9) and a projector (11) which in operation projects bright data for reflection by the eyepieces (7,9) to respective right and left eye positions (13,15). The user 17 of the helment display system is therefore presented with a display of bright data superimposed on the view of the distant scene. Each eyepiece (7,9) is supported at a respective one of two ports (27,29) of a housing arrangement (31) containing light paths leading from a bright data source (33) of the projector (11) to the eyepieces (7,9) by way of an optical system (35) of the projector (11) including a Petzval relay lens (55,57) and reflective elements (37,45,47,49,51,53). At the right port (27) there is a clear light transmissive portion (34) which is contiguous with the right eyepiece (7).

Abstract: A night vision gunsight providing an intensified image of an external scene and an image of an illuminated reticle (13,88) superimposed on the user's (14) direct view of the external scene through the sight. The sight utilizes an eyepiece (39) through which the user (14) views the external scene directly and which also incorporates an internal curved surface (57) possessing both light reflecting and light transmitting properties which serves as a collimating reflector for light rays from an image intensifier (31) viewing the external scene. Light from the illuminated reticle (13,88) may also be collimated and reflected to the user's eye (14) by the curved surface (57) in the eyepiece (39), or alternatively by a similar surface (22) incorporated in an optical element (21,23) in the user's (14) line of sight through the eyepiece (39).

Abstract: A night vision viewing system, suitable for mounting on an observer's headgear (11), wherein light rays from a forward scene pass to the observer's eye (E) via a path comprising a forward looking objective lens (23), an inclined reflector (35) which directs the rays passing through the objective onto an outwardly sideways looking input face of an image intensifier (31), and a fibre optic stub (33) which directs rays from the output face of the intensifier onto a second reflector (27) which directs the rays downwardly into an eyepiece (21) which is in the observer's forward line of sight. The eyepiece incorporates an internal surface (37) having both light reflective and light transmissive properties which directs rays entering the eyepiece from the intensifier to the observer's eye. The fibre optic stub serves to effect rotation of the intensified image to present an intensified image of correct orientation to the observer.

Abstract: A helmet mounted binocular goggle night vision viewing system comprising two independent night vision viewing arrangements, one for each eye of a wearer of the helmet, supported from above the face aperture of the helmet, each viewing arrangement comprising an optical projector arranged to project an intensified image of a scene ahead of the helmet wearer downwardly to a body of light refractive material in front of the wearer's eye having parallel flat fore and aft surfaces spanned by an upper surface via which light from the projector enters the body for reflection towards a curved partially reflective, partially transmissive surface within the body by which the light is reflected back towards the aft surface for transmission therethrough to the wearer's eye, thereby to provide the wearer with a view of the projected image superimposed on his view of the scene ahead through the body.

Abstract: A display head for a head-up display system for use in a confined space, such as a high performance aircraft cockpit. The display head has a first part (11, 13, 23, 25) adapted to be mounted on an overhead member and the remainder (15, 21, 28, 29, 31) of the display head is pivotally mounted on the first part so as to enable it to be moved readily between operative and stowed positions. In the stowed position the display head does not obstruct movement of the user's head or present an obstruction on which the user may strike his head.

Abstract: A display head (11) for a vehicle head-up display system wherein the display head combiner (35, 37) is pivotally supported by means of two kinematic chains (19, 21, 23, 23', 25, 25') so as to enable the combiner (35, 37) to be moved from an operative position to a stowed position in which the combiner (35, 37) together with its support means (19, 21, 23, 23', 25, 25') is inconspicuous.

Abstract: An electric circuit module suitable for mounting in a rack, e.g. by sliding action, in parallel spaced relationship with other similar modules, comprising a shallow box (111) having two heat conductive parts (113 and 115) each comprising one major wall of the box. The electrical components (139) of the module are mounted on the interior major surfaces of the two box parts (113 and 115) and the two parts provide heat paths between the components (139) and external surface portions (133) of the box.

Abstract: An electric circuit module arrangement adapted for mounting in racking comprising a number of modules (C) secured together in side by side relationship. Interconnections (127b, 169) between the modules are provided at one end of the module arrangement and form part of the arrangement while connectors (127a) for establishing connections with other modules outside the arrangement via a wiring arrangement separate from the module arrangement, e.g. supported on the racking, is provided at the other end of the module arrangement.

Abstract: An angular position sensor for sensing the relative angular position of a helmet worn by a passenger in an aircraft with respect to the aircraft is disclosed. The sensor includes three spaced linear photodetector arrays fixed to the aircraft, and a light source mounted on the helmet and arranged to produce a light beam which rotates cyclically about an axis in the helmet so as to successively irradiate a photodetector within each array within each cycle. A sensor attached to the helmet produces a time datum signal during each cycle. A computer uses the location within the arrays of the irradiated photodetectors, and the relative timing of the irradiations with respect to the time datum to provide the required azimuth, elevation and roll angles of the helmet.

Abstract: A night vision system comprising a helmet (1) having a transparent visor (13 or 15) before or movable to a position before the eye positions (IL, IR) of an observer wearing the helmet and a night vision device (19) having two eye pieces (22L, 22R), one for each eye, supported dependant from the helmet (11) so as to present the eye pieces (22L, 22R) of the device (19) at a short distance before the helmet wearer's eye positions and the visor (13 or 15). The device (19) is supported by means of a four-bar linkage arrangement (A,B,C,D) which constrains the eye pieces (22L, 22R) for rotational movement about the respective eye positions (IL, IR) between different operative positions, and so that the eye pieces (22L, 22R) do not make contact with the visor (13 or 15) during eye piece movement.

Abstract: A magnetic field sensor in the form of an arcuate element comprising two superimposed strips of material is described. The magnetostrictive constant along the longitudinal axis of one of the strips is greater than that of the other strip, the latter strip carrying at each end a post. In use of the sensor a single mode optical fibre is attached to the element via the posts such that the part of the fibre between the posts extends along a chord of the arc defined by the element. A variation in applied magnetic field in the plane containing the arc gives rise to a variation in the part of the fibre between the posts. Light passing through the fibre is thus phase shifted by an amount dependent on the value of the applied magnetic field.

Abstract: An optical method of measuring displacement and a sensor for use in the method comprising a light guide and a concave reflective element positioned such that one end of the light guide is at the center of curvature of the reflective element. The reflective element has different regions having different reflection coefficients for light within two different wavelength bands. A member is interposed between the end and the reflective element, the member having light transmissive properties which vary spatially over the member in a direction transverse to the optical axis of the element. The member and reflective element are supported so as to allow them to be displaced relative to one another in a direction transverse to the optical axis of the element.

Abstract: An optical projector (11) for a head-up display wherein light from a data source (15) passes through a first lens arrangement (23) and then into a wedge-shaped body (27) via a first face (29) of the body wherein the light is, in turn, internally reflected at second and third angled faces of the body (35 and 33) and then exits the body at the second face (35) to pass via a second lens arrangement (25) to the system combining (13) in a direction at an angle to that which light enters the body.The arrangement of the projector facilitates the projector having lateral dimensions dictated by the data source (e.g. a CRT) rather than the optical elements of the projector.

Abstract: A helmet mounted night vision viewing system comprising a goggle arrangement supported from above the face aperture of the helmet, the goggle comprising two independent viewing arrangements, one for each eye of a wearer of the helmet, each viewing arrangement comprising an optical projector (11, 13, 15) arranged to project an intensified image of a scene ahead of the helmet wearer downwardly to an eyepiece (17) in the form of a body of refractive material (20) in front of the wearer's eye wherein light from the optical projector is reflected at an aft surface (23), towards a curved reflective surface (25) from which the light is reflected back towards the aft surface for transmission therethrough to the wearer's eye.

Abstract: A clamp arrangement for clamping a marginal portion of a board between two opposed substantially flat parallel walls. The mechanism is mounted on the board and is arranged to be capable of expansion in a direction normal to the board. The mechanism comprises an elongate spring strip extending in the direction of its length along the marginal portion, and having corrugations transverse to its length. An elongate cam overlies the spring strip, the cam having a plurality of cam surfaces along its length spaced apart at the same pitch as the spring strip corrugations. Clamping is obtained by sliding the cam relative to the spring strip bringing the cam surfaces into contact with the corrugations, thus causing expansion of the mechanism and subsequent pressure on the two opposed walls due to compression of the spring corrugations.

Abstract: An assembly comprising a board 1 and a mechanism 17 for clamping a marginal portion of the board adjacent an edge between two opposed substantially flat parallel walls 7a. The mechanism 17 is mounted on a major surface 19 of the board 1 and includes a spring strip 21 extending longitudinally along the mechanism, and having corrugations transverse to its length. An elongate cam 27 extends along the length of the strip 21, overlying the strip, and being supported for rotation about its longitudinal axis. Rotation of the cam 27 causes expansion of the mechanism 17 in a direction normal to the surface 19, limitation of the expansion by the walls 7a leading to compression of the corrugations in the strip 21.

Abstract: An optical device suitable for attachment to headgear (13) such as a pilot's helmet, for use as a night vision goggle (11) wherein an image intensifier (19a or 19b) whereby radiation in the visible and/or near infra-red portions of the spectrum received from the scene to be viewed is converted to visible light is arranged so that its input (33a or 33b) and output (21a or 21b) faces are directed respectively away from and towards the scene to be viewed, light from the output face being reflected to the user's eyes by a viewing eyepiece (23a or 23b) which intercepts the user's line of sight, and the received radiation being directed onto the input face by an objective and ray-folding means (27a or 27b; 29a or 29b; 31a or 31b). A design of goggle which is lighter and has a smaller forward projection can be achieved in goggles using such optical devices.