Abstract: An Electrically Switchable Bragg Grating (ESBG) despeckler device comprising at least one ESBG element recorded in a hPDLC sandwiched between transparent substrates to which transparent conductive coatings have been applied. At least one of said coatings is patterned to provide a two-dimensional array of independently switchable ESBG pixels. Each ESBG pixel has a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.

Abstract: An Electrically Switchable Bragg Grating (ESBG) despeckler device comprising at least one ESBG element recorded in a hPDLC sandwiched between transparent substrates to which transparent conductive coatings have been applied. At least one of said coatings is patterned to provide a two-dimensional array of independently switchable ESBG pixels. Each ESBG pixel has a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.

Abstract: An Electrically Switchable Bragg Grating (ESBG) despeckler device comprising at least one ESBG element recorded in a hPDLC sandwiched between transparent substrates to which transparent conductive coatings have been applied. At least one of said coatings is patterned to provide a two-dimensional array of independently switchable ESBG pixels. Each ESBG pixel has a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.

Abstract: An Electrically Switchable Bragg Grating (ESBG) despeckler device comprising at least one ESBG element recorded in a hPDLC sandwiched between transparent substrates to which transparent conductive coatings have been applied. At least one of said coatings is patterned to provide a two-dimensional array of independently switchable ESBG pixels. Each ESBG pixel has a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.

Abstract: An apparatus for recording a holographic device comprises: a master hologram comprising a multiplicity of holographic elements each characterized by one of a predefined set of grating prescriptions; a transparent substrate supporting a layer of holographic material; and a light source. Each holographic element diffracts source light onto a predefined region of the layer. Each prescription modulates at least one of phase, amplitude, and angle of the light. There is further provided a method of recording a holographic device, comprising the steps of: providing said apparatus; exposing the master to illumination from the source; and diffracting light from each holographic element onto a predefined region of the layer.

Abstract: An apparatus for recording a holographic device comprises: a master hologram comprising a multiplicity of holographic elements each characterized by one of a predefined set of grating prescriptions; a transparent substrate supporting a layer of holographic material; and a light source. Each holographic element diffracts source light onto a predefined region of the layer. Each prescription modulates at least one of phase, amplitude, and angle of the light. There is further provided a method of recording a holographic device, comprising the steps of: providing said apparatus; exposing the master to illumination from the source; and diffracting light from each holographic element onto a predefined region of the layer.

Abstract: An internal device having a lightguide which cooperates with an internal light source. A first light coupling element couples an external light source to the lightguide and a second light coupling element extracts the total internal reflection (TIR) from the lightguide. Between the first and second lightguides, an angular grating device and phase grating device are imposed. The angular grating device applies angular diversity to the rays of the TIR light, while the phase grating device applies phase diversity to the rays of the TIR light. Each of the grating devices has a plurality of electrically switchable grating pixels having a unique first and second diffracting state which varies based on the applied voltage.

Abstract: An Electrically Switchable Bragg Grating (ESBG) despeckler device comprising at least one ESBG element recorded in a hPDLC sandwiched between transparent substrates to which transparent conductive coatings have been applied. At least one of said coatings is patterned to provide a two-dimensional array of independently switchable ESBG pixels. Each ESBG pixel has a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.

Abstract: An Electrically Switchable Bragg Grating (ESBG) despeckler device comprising at least one ESBG element recorded in a hPDLC sandwiched between transparent substrates to which transparent conductive coatings have been applied. At least one of said coatings is patterned to provide a two-dimensional array of independently switchable ESBG pixels. Each ESBG pixel has a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.

Abstract: An internal device having a lightguide which cooperates with an internal light source. A first light coupling element couples an external light source to the lightguide and a second light coupling element extracts the total internal reflection (TIR) from the lightguide. Between the first and second lightguides, an angular grating device and phase grating device are imposed. The angular grating device applies angular diversity to the rays of the TIR light, while the phase grating device applies phase diversity to the rays of the TIR light. Each of the grating devices has a plurality of electrically switchable grating pixels having a unique first and second diffracting state which varies based on the applied voltage.

Abstract: An Electrically Switchable Bragg Grating (ESBG) despeckler device comprising at least one ESBG element recorded in a hPDLC sandwiched between transparent substrates to which transparent conductive coatings have been applied. At least one of said coatings is patterned to provide a two-dimensional array of independently switchable ESBG pixels. Each ESBG pixel has a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.

Abstract: An Electrically Switchable Bragg Grating (ESBG) despeckler device comprising at least one ESBG element recorded in a hPDLC sandwiched between transparent substrates to which transparent conductive coatings have been applied. At least one of said coatings is patterned to provide a two-dimensional array of independently switchable ESBG pixels. Each ESBG pixel has a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.

Abstract: An Electrically Switchable Bragg Grating (ESBG) despeckler device comprising at least one ESBG element recorded in a hPDLC sandwiched between transparent substrates to which transparent conductive coatings have been applied. At least one of said coatings is patterned to provide a two-dimensional array of independently switchable ESBG pixels. Each ESBG pixel has a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.

Abstract: An Electrically Switchable Bragg Grating (ESBG) despeckler device comprising at least one ESBG element recorded in a hPDLC sandwiched between transparent substrates to which transparent conductive coatings have been applied. At least one of said coatings is patterned to provide a two-dimensional array of independently switchable ESBG pixels. Each ESBG pixel has a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.

Abstract: An Electrically Switchable Bragg Grating (ESBG) despeckler device comprising at least one ESBG element recorded in a hPDLC sandwiched between transparent substrates to which transparent conductive coatings have been applied. At least one of said coatings is patterned to provide a two-dimensional array of independently switchable ESBG pixels. Each ESBG pixel has a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.

Abstract: An Electrically Switchable Bragg Grating (ESBG) despeckler device comprising at least one ESBG element recorded in a hPDLC sandwiched between transparent substrates to which transparent conductive coatings have been applied. At least one of said coatings is patterned to provide a two-dimensional array of independently switchable ESBG pixels. Each ESBG pixel has a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.

Abstract: An Electrically Switchable Bragg Grating (ESBG) despeckler device comprising at least one ESBG element recorded in a hPDLC sandwiched between transparent substrates to which transparent conductive coatings have been applied. At least one of said coatings is patterned to provide a two-dimensional array of independently switchable ESBG pixels. Each ESBG pixel has a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.

Abstract: An optical device comprises a waveguide assembly having a number of core portions along which radiation can propagate from an input port to an output port and cladding portions abutting said core portions. Each core portion is adapted to receive a beam composed of a respective wavelength band of radiation. The device also comprises a demultiplexer for separating a signal comprising a plurality of channels into separate channel beams for input into the waveguide and/or a multiplexer fro receiving the beams from the waveguide and recombining them into a single signal. Preferably, the waveguide incorporates optical attenuation means operative on the beams. In one embodiment, the core portions and/or abutting cladding portions are comprised of a polymer-dispersed liquid crystal material whose refractive index can be varied by the application of an electrical stimulus.

Abstract: A layer of optically active material overlaps the mode filed of a single mode optical waveguide and has regions to which electric fields can be applied by way of respective electrodes so as to vary the refractive index of the layer in those regions. The regions are spaced apart longitudinally of the waveguide, and the fields are so arranged that they extend at different angles to an interface between the waveguide and the layer and act sequentially upon different polarisation components of radiation propagating along the waveguide. In one arrangement, the fields are orthogonal to one another. In an alternative arrangement, the third field can be applied to a further longitudinally-spaced region of the layer and the three fields are arranged at 120 degrees to one another.

Abstract: Light from an image displayed on a display screen 10 is transmitted to an observer's eye 11 by way of a dynamic optical element 12 (such as a spatial light modulator or an electrically switchable holographic composite) which acts as a lens. The characteristics of the dynamic optical element 12 can be altered so that it acts sequentially to direct light of different colors to the observer's eye. In one optional embodiment emitters 17 on the display screen 10 emit infra-red radiation which is projected by the dynamic lens 12 as a broad wash onto the eye 11. Infra-red radiation reflected back from the eye 11 is focussed by the dynamic lens 12 onto detectors 18 also provided on the display screen 10. The detectors 18 are thus able to sense the direction of eye gaze, and the dynamic lens 12 is controlled in dependence on this to create an area of high resolution in an area of interest centered on the direction of gaze, which is moved to follow the eye gaze as its direction alters.