Abstract: A distributed optical fibre sensor to measure one or more parameters of an environment as functions of position along a sensing optical fibre passing through the environment, and determines, measures or calculates an OTDR trace or attenuation profile of a sensing optical fibre in a distributed optical fibre sensor. The OTDR trace is to monitored to provide an indicia of properties of the sensing optical fibre in order to determine if the performance of the distributed optical fibre sensor in accurately measuring the desired environmental parameters is compromised. This allows adjustment of operation parameters of the distributed optical fibre sensor to maintain the performance at acceptable levels, or to automatically control the distributed optical fibre sensor in order to at least partly compensate for the changing properties. A distributed optical fibre sensor having such capability is also disclosed.

Abstract: There is disclosed a distributed optical fiber sensing system in which the sensor fiber comprises at least first and second waveguides used for separate sensing operations. The sensor fiber may be, for example, a double clad fiber having a monomode core and a multimode inner cladding.

Abstract: There is disclosed a distributed optical fibre sensing system in which the sensor fibre comprises at least first and second waveguides used for separate sensing operations. The sensor fibre may be, for example, a double clad fibre having a monomade core and a multimode inner cladding.

Abstract: There is disclosed a distributed optical fiber sensing system in which the sensor fiber comprises at least first and second waveguides used for separate sensing operations. The sensor fiber may be, for example, a double clad fiber having a monomode core and a multimode inner cladding.

Abstract: A projection display (60) includes a first waveguide (64) incorporating a grating structure (74) and second waveguide (66) incorporating an exit grating (84). The first and second waveguides (64, 66) are arrange to expand an image in orthogonal directions. The second waveguide (66) includes a first layer (86) with a first predetermined refractive index and/or first predetermined thickness, a second layer (88) with a second predetermined refractive index and/or second predetermined thickness. The exit grating (84) is arranged to direct at least some impinging light out of the second waveguide(66) and to provide at least some beam splitting of light passing through the exit grating (84). The first and second layers (86, 88) are arranged to abut one another such that the exit grating (84) is therebetween.

Abstract: There is disclosed a distributed optical fibre sensing system in which the sensor fibre comprises at least first and second waveguides used for separate sensing operations. The sensor fibre may be, for example, a double clad fibre having a monomode core and a multimode inner cladding.

Abstract: An imaging device, particularly but not exclusively for use in a targeting sensor for missile seekers. The imaging device including at least one lens; a substantially planar sensor having a plurality of pixels; a light guiding arrangement for directing light received via said lenses toward said sensor; in which said light guiding arrangement includes a plurality of light guides.

Abstract: An apparatus and method are provided for monitoring, remotely, information relating to the motion of at least one moving object. The apparatus comprises: means for illuminating a retro-reflective data carrier mounted on each moving object, in particular when the moving object is located at a predetermined monitoring position; means for detecting, in optical signals returned by the retro-reflective data carrier, data representing a timing trigger and data representing an identifier for the at least one moving object; timer means responsive to a timing trigger detected at the predetermined monitoring position to trigger a timer associated with a detected identifier; and an output to provide timing information associated with the detected identifier, and hence relating to the at least one moving object at the predetermined monitoring position. The timing information may be used to derive relative ordering, relative timing or speeds of moving objects, for example.

Abstract: A fluidic lens for use with IR light is provided having an optically transparent cavity containing a liquid perfluorocarbon retained within the cavity at least in part by an optically transparent flexible membrane whose surface profile may be varied by applying a variable pressure to the liquid within the cavity.

Abstract: A method is provided for laminating optical substrates and in particular for manufacturing a thin combiner for an optical display that preserves the flatness of the component parts and ensures an even separation of layers, in particular an optical substrate and a thin cover plate that is to be bonded to the substrate. In the method, spacer particles in a predetermined size range are included within a glue layer at a required density to ensure cover plate flatness and uniform separation during assembly.

Abstract: A projection display (60) includes a first waveguide (64) incorporating a grating structure (74) and second waveguide (66) incorporating an exit grating (84). The first and second waveguides (64, 66) are arrange to expand an image in orthogonal directions. The second waveguide (66) includes a first layer (86) with a first predetermined refractive index and/or first predetermined thickness, a second layer (88) with a second predetermined refractive index and/or second predetermined thickness. The exit grating (84) is arranged to direct at least some impinging light out of the second waveguide(66) and to provide at least some beam splitting of light passing through the exit grating (84). The first and second layers (86, 88) are arranged to abut one another such that the exit grating (84) is therebetween.

Abstract: An imaging device, particularly but not exclusively for use in a targeting sensor for missile seekers. The imaging device including at least one lens; a substantially planar sensor having a plurality of pixels; a light guiding arrangement for directing light received via said lenses toward said sensor; in which said light guiding arrangement includes a plurality of light guides.

Abstract: A retroreflective device comprising a substantially spherical graded refractive index lens, referred to as a GRIN-sphere lens (2), a reflective part for retroreflecting (6) a radiation beam (B) passing through the graded refractive index lens and, at least partially surrounding the lens, a transparent material (4) having a substantially uniform refractive index.