Abstract: An optical projector arrangement includes a light source. Light from the light source is formed into a collimated beam travelling along an axis by optics. The light is split into red, green and blue components travelling in different paths by a splitter. The components are subsequently recombined by a synthesizer to continue along the axis to a projection lens. A respective liquid crystal modulator is included in each different path. In order to increase the optical length of the path taken by the green component so that it is equal to the lengths of the paths taken by the red and blue components, a path length compensator is included in the path for the green component, which path would otherwise be along the axis for the whole of its length.

Abstract: An access control system for a public transport system comprises, at each entrance/exit location (1) of the transport system, at least one entrance gate (12) provided with a ticket reader (8), at least one exit gate (20) provided with a ticket reader (16), a ticket issuing machine (22) and a local data processor (10) with which the other items communicate. The local processors (10) communicate via a central processor (14). The tickets bear unique identification codes which are stored, upon issue, in the local processors (10) at the location (1) at which they are valid for entry. Upon entry using a ticket the relevant code is cancelled at all locations and then it is stored again in the local processors (10) at those locations (1) at which it is valid for exit. Upon exit using a ticket the relevant code is cancelled at all locations. If entry or exit is attempted at a location (1) at which the relevant code is not stored, the relevant gate (12 or 20) is barred.

Abstract: Apparatus for irradiating an area with a controllable pattern of light comprises a laser (2), which illuminates a spatial light modulator (6). The resulting spatially modulated light then passes to a cholesteric liquid crystal polymer beam-splitter (10) which reflects it to an image surface (13) of an endoscope (12). The endoscope relays it to another image surface (40) whence it is focussed on the area to be irradiated. This light may be used for photodynamic therapy.

Abstract: A matrix of bistable pixels defined by ferroelectric liquid crystal material situated at the areas of overlap of row and column electrodes is addressed by blanking the rows and subsequently setting selected pixels to the unblanked state row by row by applying a select waveform (21) to the relevant row electrode while applying charge-balanced data waveforms (35 or 37) in parallel to the column electrodes. One data waveform (35) leaves the corresponding pixel in the blanked state while the other (37) switches it to the unblanked state. Each data waveform comprises a pair of contiguous pulses (39, 41 or 45, 47) the transition between which coincides with the start of the select pulse (31). In order to prepare each pixel to be switched or non-switched the first pulse (39 or 45) of each pair is longer than the select pulse (31).

Abstract: An ammonia gas sensor 16 is housed within a container 14 partially immersed in a solution 2 containing ammonium ions. An electrochemical generator 6, 8, 10 generates hydroxyl ions in a region of the solution 2 adjacent the container 14. This converts ammonium ions to ammonia gas which is sensed by the sensor 16 having passed through a gas-permeable member 12. This sensing provides an indication of the concentration of ammonium ions in the solution 2.

Abstract: A plasma processing device is described which is modular and can be scaled up by assembly together with similar devices to provide a capability for large area processing. The device includes a housing which contains an array of RF coils and into which a process gas is fed. The article to be processed is disposed close to the housing and egress of the process gas from the housing to the process region is resisted so as to maintain a positive pressure differential between the housing and the process region.

Abstract: A finger guide (2) comprises first and second orthogonally-oriented portions (4,12) each comprising a pair of opposed converging surfaces (6,8;14,16) into which the end and the shank, respectively, of a finger for examination fit. Because of the relative orientation of the surfaces, movement of the finger relative to an examination surface (22) is reproducibly constrained.