Abstract: Apparatus for displaying an image suspended in space above a horizontal surface such as a tabletop or vehicle dash-board, of an original image below the surface, comprises a beam-splitter window in the surface and a retroreflector below the surface in a path for light reflected by the beamsplitter. The original image may for example be a VDU screen or vehicle instrument panel.

Abstract: A method of assaying for a ligand in a sample involves incubating the sample in contact with a specific binding partner for the ligand carried on one surface of an optical structure, irradiating the structure at a suitable angle or range of angles to the normal such that the resonance and/or total internal reflection of the radiation occurs within the optical structure and/or the layer of specific binding partner, and analyzing the radiation in order to determine whether, and if desired the extent to which and/or rate at which the generated radiation and/or optical characteristics of the optical structure are altered by complex formation.

Abstract: A border for a substantially two-dimensional image comprises an anterior pattern and a posterior pattern, the patterns being space one from the other and being arranged to form, when viewed together, a resultant apparent pattern in a different plane to that of the image. The patterns each comprise relatively brighter and relatively darker regions, but each usually has a different pitch. The posterior pattern may advantageously comprise an array of reflective dots printed onto a major surface of a light transmissive sheet which may be edge lit by a light source. The border brightness can then be independent of ambient light conditions and simple to manufacture.

Abstract: An imaging system for the generation of an apparent three-dimensional (3-D) image suspended in space for direct vieiwing includes a beamsplitter and a retroreflector. The optical property of reflecting light back along its original path enable the system to generate such an apparent 3-D image based on the perception of depth cues present in the original scene for viewing.

Abstract: A liquid crystal display comprises a liquid crystal material layer contained between transparent slides which carry electrodes arranged in lines and columns to form an x, y matrix with x, y intersections. The liquid crystal layer at the intersections are turned on line by line by a blanking voltage, turned off by application of a zero voltage, and held at a threshold voltage at other times. The voltages are applied from a two phase supply in the form of two sinusoidal waves spaced 60.degree. apart in phase. Threshold voltages at an intersection are maintained by applying one of the two waveforms to x electrodes and a zero voltage to y electrodes. A zero voltage at x, y intersections is arranged by applying the other of the two waveforms to both x, y electrodes.

Abstract: A liquid crystal display comprises a liquid crystal material layer contained between transparent slides which carry electrodes arranged in lines and columns to form an x, y matrix with x, y intersections. The liquid crystal layer at the intersections are turned on line by line by a blanking voltage, turned off by application of a zero voltage, and held at a threshold voltage at other times. The voltages are applied from a three phase supply by applying one phase to x electrodes a second phase to the y electrodes to maintain a threshold voltage at x, y intersections, and applying the third phase to both x, y electrodes for turning an intersection off. Alternatively the voltages may be applied from a two different frequency waveform supply.

Abstract: A liquid crystal device includes a sheet of plastic material having an open pore structure in which a liquid crystal material has been introduced. The liquid crystal material may be dichroic and contain one or more dyes which may be dichroic. The liquid crystal material may be nematic or cholesteric or a mixture of these two or a smectic material. Protective layers of plastic or glass may be arranged to enclose the sheet and the protective layer may carry electrodes. The liquid crystal may be applied to selected portions only of the sheet and the remaining parts of the sheet filled with a non-mesomorphic material.

Abstract: A liquid crystal guest-host display device includes a dye dissolved in the liquid crystal material. The invention is characterized in that the dye comprises three colored dye compounds mixed together to provide gray in the absence of an applied electric field. The compounds may be Sudan Black, Sudan Red and .beta.-carotene. The liquid crystal material preferably includes at least one 4'-alkyl- or -alkoxy-4'-cyanobiphenyl compound.

Abstract: A color display system, for example an electronic data display or a color television system incorporates a display screen, for example a cathode ray tube phosphor, and at least one liquid crystal color filter. The screen emits light in the form of visual information in at least two colors, and the filter is controlled electrically in such a way that the colors transmitted by the screen may be switched according to input signal used to energize the screen.