Abstract: The invention relates to optical beam steering. There is described an optical beam steering apparatus, comprising: a splitter arranged to split an optical beam into at least a first part having a first polarisation and a second part having a second polarisation, said first and second polarisations being substantially mutually orthogonal; a first liquid crystal device region arranged to receive said first part and to have director orientation substantially aligned to said first polarisation; and a second liquid crystal device region arranged to receive said second part and to have director orientation substantially aligned to said second polarisation.

Abstract: A method of forming an image comprising providing a device for imparting respective phase shifts to different regions of an incident wavefront, wherein the phase shifts give rise to an image in a replay field, and causing zero-order light to be focused into a region between the replay field and the device.

Abstract: A method of displaying a video image comprises receiving sequential image frames at a processor. Each image frame is processed to obtain a kinoform. A programmable diffractive element such as an SLM represents the sequence of kinoforns allowing reproduction of the image using a suitable illumination beam.

Abstract: A smart pixel is comprised by a chiral smectic liquid crystal light modulator (45) (ferro-electric or electroclinic) disposed on a semiconductor substrate and having associated therewith electronic circuitry (41-44) formed in the semiconductor substrate in particular a single crystal silicon VLSI substrate, which circuitry is such as to provide localised intelligence (electrical signal processing and conditioning, pointwise operations, logic functions) at the modulator. The circuitry may comprise photodetector/threshold circuitry (FIG. 7) or digital-to-analogue conversion (FIGS. 3 or 4), for example.

Abstract: A neural plane, which can form the basis of a neural network or a component thereof, is comprised by an optical modulator, an electrical non-linearity circuit and an optical detector interconnected whereby in use the non-linearity circuit controls the modulator in dependence on the detector output. There are parallel arrays (10, 11, 12) of such modulators, non-linearity circuits and detectors (M, T, D, 30, 33, 34). The modulator, non-linearity circuits and detectors have components formed in a common semiconductor substrate (20), for example by VLSI techniques with a silicon substrate, the modulators (30) may be comprised by liquid crystal on silicon in that case (FIGS. 4, 7).

Abstract: An optical logic device consists of a bistable liquid crystal layer (BOD 1) of the thermally-induced birefringent (TIB) type settable by one or more write beams and rfead by a beam of a different wavelength or different light polarization. Thus the read and write beams are optically decoupled. Two such devices (BOD 1 and BOD 2) in tandem form a 3-input AND gate. Here beams A and B are write beams for the first device, (BOD 1), and beam C is the read beam for the first device. For the second device (BOD 2) the write beams are the output of the first device (BOD 1) and beam D, the read beam being beam E. The two read beams have different wavelengths from the write beam. In a second version, the liquid crystal layer is on the base of a prism via which the beams reads it. Write beams go right through the layer, while a read beam is "reflected" from the layer but is modulated by the state thereof. This is an OR gate. Logic assemblies can use combinations of such AND or OR gates.

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: 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`.