Abstract: Apparatus and methods are described for of measuring amplitude and phase variations in a spatially coherent beam of light. A beam of coherent light is made incident upon a spatial array of phase modulating elements displaying a pixellated first phase distribution. In a measuring region of said spatial array, the phase distribution is changed to a new value while retaining the first phase distribution outside the measuring region, for example by flashing a single pixel. The change in intensity resulting from the change in phase distribution is then determined.

Abstract: A beam steering device uses a liquid crystal with an array of back electrodes. Voltages are applied to the array to cause a desired phase distribution across the array, the distribution being selected to steer a beam incident upon the array into a desired direction. Reflective elements are disposed to reflect light incident in the spaces between the electrodes to reduce losses and to smooth the transitions in phase between adjacent electrodes.

Abstract: To operate an optical device comprising an SLM with a two-dimensional array of controllable phase-modulating elements groups of individual phase-modulating elements are delineated, and control data selected from a store for each delineated group of phase-modulating elements. The selected control data are used to generate holograms at each group and one or both of the delineation of the groups and the selection of control data is/are varied. In this way upon illumination of the groups by light beams, light beams emergent from the groups are controllable independently of each other.

Abstract: To operate an optical device comprising an SLM with a two-dimensional array of controllable phase-modulating elements groups of individual phase-modulating elements are delineated, and control data selected from a store for each delineated group of phase-modulating elements. The selected control data are used to generate holograms at each group and one or both of the delineation of the groups and the selection of control data is/are varied. In this way upon illumination of the groups by light beams, light beams emergent from the groups are controllable independently of each other.

Abstract: To operate an optical device comprising an SLM with a two-dimensional array of controllable phase-modulating elements groups of individual phase-modulating elements are delineated, and control data selected from a store for each delineated group of phase-modulating elements. The selected control data are used to generate holograms at each group and one or both of the delineation of the groups and the selection of control data is/are varied. In this way upon illumination of the groups by light beams, light beams emergent from the groups are controllable independently of each other.

Abstract: An optical switch uses two ferroelectric liquid crystal spatial light modulators (10, 11) with an interconnect region in between. The switch uses bulk lenses (2, 8) to focus light from an input fibre array (1) to a first spatial light modulator (10), and from the second spatial light modulator (11) to an output array (9). Each spatial light modulator displays a respective hologram selected from a previously calculated set, to cause a desired switching of light from the input fibre array to the output array.

Abstract: An optical switch uses a polarization insensitive spatial light modulator operating by a double pass through a liquid crystal cell. The switch includes two such modulators in a cross bar arrangement. Different embodiments employing techniques for reducing cross talk are described.

Abstract: An optical fiber has a core, an inner cladding and an outer cladding on. In a first region the inner cladding refractive index has a first value which differs from the core refractive index by about 0.0045. The inner cladding refractive index changes along said fiber from the first value to a second value at a free-space end. The second value matches the core refractive index, so that the effective diameter of the core at the free-space end is that of the core plus the inner cladding. Hence the outer cladding acts to constrain the light in the end region. The spot-size and the V number (normalized frequency) are increased, thereby increasing offset tolerances.

Abstract: A powdered coating composition comprises a thermosetting resin which consists of two components. The first component includes an acid reactive material comprising a polyepoxide or &bgr;-hydroxyalkylamide compound. The second component is an acid terminated resin which reacts with the first component. A curing agent including a polycarboxylic acid having a functionality of at least 3 and a source of tertiary or quanternary nitrogen is present to react with an excess of the first component, thereby curing thermosetting resin.

Abstract: Process for the selective hydrogenation of alphatic or aromatic substrates under supercritical or near critical conditions. Hydrogenation is effected using a heterogeneous catalyst in a continuous flow reactor containing a supercritical or near critical reaction medium and selectively of product formation is achieved by varying one or more of the temperature, pressure, catalyst and flow rate.

Abstract: A device for detecting ultraviolet radiation comprises a measuring head (101) to receive the ultraviolet radiation and comprising a filter (112) which emits fluorescent light in an amount dependent on the amount of ultraviolet radiation. The fluorescent light emitted is monitored to obtain a measure of the amount of ultraviolet radiation. A means (115) may be included to compensate for the temperature dependence of the filter.

Abstract: The solidification characteriztics of a solidifiable liquid film are monitored by effecting relative movement between a stylus and the film and monitoring the resistance to movement of the stylus through the film as the film is solidifying. The film may be subjected to ultraviolet radiation or elevated temperature to cause solidification. The resistance to movement may be monitored electrically in which case it may be recorded as a trace or a chart recorder.

Abstract: The pot life of a mixture of an epoxide resin and a curing agent comprising a compound containing a plurality of amine groups is improved by carbonating the curing agent.