Abstract: Optical four wave mixing is provided by interfering two waves on a liquid crystal layer (1) temperature stabilized just beneath its nematic/isotropic phase change transition temperature. The liquid crystal incorporates a guest dye to absorb the light producing a holographic thermal image which is accompanied by a holographic phase image. Once this phase image starts to build up it is illuminated with a `third wave` of light that is not absorbed so as to produce the required holographically diffracted `fourth wave`.

Abstract: Bistable operation of ferroelectric liquid crystal smectic I* or smectic F* cells is disclosed which uses a greater liquid crystal layer thickness than is achievable with smectic C* material while yet retaining bistability of operation. One or more such cells are employed in two-dimensional information processing apparatus.

Abstract: The data processing terminal comprises a smectic liquid crystal flat panel display module (2) which is supported by a support module (1). The terminal also includes a keyboard (4). The display module (2) may be removed from the support module (1) and has its own central processor, memory, control means and power source to enable it to operate independently of the support module, which contains its own central processor, memory, control means, and interface means and is mains operated. The display module may incorporate a touch sensitive overlay to permit the manipulation of the contents of the display. The support unit may incorporate a telephone interface unit.

Abstract: A laser beam addressed smectic display in which the laser beam is used to write clear tracks in an optically scattering field employs an anisotropic conductivity dopant in the liquid crystal filling so that the cell can be electrically set into the scattering state by means of dynamic scattering effects. This requires the use of a laser light absorbing dye that is not only photochemically stable, but also stable against the effects of the relatively high fields and currents present when the cell is being set into the scattering state.

Abstract: A ferro-electric liquid crystal display in which the individual pixels are addressed via an address matrix that includes one field effect transistor for each pixel, and a plurality of row and column conductors whereby data is written into each pixel to change or to maintain its display condition.

Abstract: Optical four wave mixing is provided by interfering two waves on a liquid crystal layer (1) temperature stabilized just beneath its nematic/isotropic phase change transition temperature. The liquid crystal incorporates a guest dye to absorb the light producing a holographic thermal image which is accompanied by a holographic phase image. Illumination of this phase image with a `third wave` of different wavelength is then used to produce the required holographically diffracted `fourth wave`.

Abstract: A relatively shallow arrangement for providing illumination for a light scattering type display cell employs a transparent sheet in optical contact with the front surface of the cell and a matte black sheet out of contact with the rear surface. The assembly acts as a light guide for light launched into at least one of the transparent sheet from at least one strip lamp. The only light escaping from the display, etc. in the direction of the observer is a proportion of that scattered into non-guided directions by regions of liquid crystal layer selectively set into a scattering state.

Abstract: A coherent light image generator for signal processing such as image correlation directs laser light onto a specularly reflecting matrix addressed dyed nematic liquid crystal display device having a liquid crystal layer sandwiched between a transparent electroded front plate and an active single crystal silicon wafer incorporating NMOS circuitry.

Abstract: A co-ordinate matrix addressing system is used to address a liquid crystal display cell containing a positive dielectric anisotropy smectic material. For this purpose one or more direct voltage pulses are applied across selected elemental volumes of the display to convert them from a focal-conic scattering state to a homeotropically aligned state. Prior to this all elements are electrically driven into the turbulent scattering state which relaxes into the focal-conic scattering state upon removal of the driving field. The driving field may also take the form of direct voltage pulses. Unselected elemental volumes may be refreshed to substantially their original level of focal-conic scattering by means of a suitable blanking potential applied to both selected and unselected elemental volumes which nevertheless leaves previously restored elemental volumes in the homeotropically aligned state.

Abstract: A curtailed drive scheme for a matrix array liquid crystal display cell in which the field developed across each picture element is maintained for only a fraction of the time interval between consecutive addressings. This reduces the effects of differences in time constants across the display for addressing schemes in which the average time constant is short compared with this time interval between consecutive addressings.

Abstract: A co-ordinate matrix addressing system is used to address a liquid crystal display cell containing a positive dielectric anisotropy smectic material. For this purpose one or more direct voltage pulses are applied across selected elemental volumes of the display to convert them from a focal-conic scattering state to a homeotropically aligned state. Prior to this all elements are electrically driven into the turbulent scattering state which relaxes into the focal-conic scattering state upon removal of the driving field. The driving field may also take the form of direct voltage pulses.

Abstract: An internally electroded smectic liquid crystal display cell having a layer of a smectic material sandwiched between two electroded plates having electrodes that overlap at least in part wherein each said electrode is covered with an electrically insulating coherent layer whose surface has been treated to provide it with a rough texture provides a liquid crystal display cell of low voltage threshold characteristics.

Abstract: In a liquid crystal cell parallel homogeneous alignment of the liquid crystal molecules is provided by rubbing a silica or silica containing film produced by firing a silica containing organic coating applied in liquid form. The alignment provided by this process can withstand firing temperatures in the range 450.degree. to 500.degree. C. normally employed for making fused glass frit perimeter seals. By incorporating titania into the film the refractive index can be matched with that of the underlying electrodes and so render them substantially invisible.

Abstract: A liquid crystal display cell provides more than two contrasting colors that operates in a storage mode which has a positive dielectric anisotropy smectic liquid layer between electroded plates treated to produce parallel homogeneous alignment with a very large tilt angle. The tilt angle can be progressively increased by increasing the strength of an applied alternating potential thereby producing Newtonian colors when viewed through crossed polarizers. When pseudo-homogeneous zero tilt alignment is provided, a pleochroic dye may be mixed with the smectic to provide a color when the layer is in the pseudo-homogeneous alignment state. An applied electric field converts this to homeotropic alignment.

Abstract: A liquid crystal temperature indicator that gives a visual indication of whether the device is at a temperature above or below one or more threshold values has a homeotropically aligned nematic or smectic layer incorporating a pleochroic dye. The color of the cell changes as the dye will only absorb normally incident light when the temperature causes the liquid to go isotropic. Electrodes may be provided to provide electronic detection of the passage of the liquid through the threshold temperature.

Abstract: A method for preparing and operating dynamic scattering liquid crystal display cells having internal electrodes and containing a smectic liquid having positive dielectric anisotropy and incorporating a homeotrophic alignment inducing medium for the smectic liquid filling. The cell can be switched off to make the transition from dynamic scattering to static scattering for providing indefinite storage properties.

Abstract: A method of controlling the spacing between the panels in large area liquid crystal cells consisting of the application of an array of spacer dots on one panel and an array of tie dots on the other panel. Upon firing the panels, the spacer dots remain rigid to define the spacing whereas the tie dots soften and deform.

Abstract: A cholesteric filled liquid crystal cell has one surface homeotropically aligned and the opposite surface homogeneous parallel aligned. Plane polarized light incident upon the homogeneous parallel aligned surface with its polarization plane parallel with or orthogonal to the alignment direction has its plane of polarisation rotated by an amount controllable by the application of an electric potential across the cell. This forms the active element of a simulated rotating pointer meter display having no moving parts and only a single pair of electrical inputs.