Abstract: A transparent solar concentrator is provided for converting solar energy into electrical energy. The solar concentrator includes a first light transmissive substrate, a plurality of solar cells for receiving solar energy and converting the solar energy into electrical energy, the plurality of solar cells positioned relative to the first substrate, and a plurality of light redirecting elements arranged in the first light transmissive substrate. Each of the plurality of light redirecting elements is configured to direct light incident on a first side of the first light transmissive substrate to a respective one of the plurality of solar cells on an opposite side of the first light transmissive substrate.

Abstract: A display comprises: a single-view image display panel (6); and a parallax optic (8) disposed over a display face of the image display panel for restricting the angular spread of light output from the display face of the image display panel. This enables light to be concentrated in a desired viewing angle range (66), and avoids a user (56) seeing unwanted reflections that may occur as a result of a greater viewing angle range (64) if the parallax optic (8) is not provided. The display may be used, as an example, in a motor vehicle to prevent unwanted reflections from the windscreen (62) of the vehicle.

Abstract: A low concentration solar apparatus for collecting solar radiation and concentrating it to a receiving device such as a photovoltaic cell or thermovoltaic cell, comprising a non-tracked waveguide concentrator with integral light turning element. It is thus possible to provide a solar apparatus for generating power in a very cost effective manner compared to conventional solar apparatus such as photovoltaic modules.

Abstract: A backlight for illuminating a liquid crystal display in which LEDs are arranged in an array in a backlight cavity. The LEDs are arranged such that the emission from the LEDs is in a lateral direction into the backlight cavity. The emission from the LEDs is shaped so as to match the cross-sectional shape of the backlight cavity thus achieving a high degree of spatial uniformity for a relatively small backlight cavity thickness.

Abstract: A transflective liquid crystal display (70) comprises a liquid crystal cell (38) disposed between a front substrate (40) and a rear substrate (36), a front polarizer (46) located in front of the front substrate (40) and a rear polarizer (32) located behind the rear substrate (36), a front retarder (42, 44) located between the front substrate (40) and the front polarizer (46), a rear retarder (62, 64) located between the rear substrate (36) and the rear polarizer (32), and a light source (30) located behind the rear polarizer (32). A transflective display having a number of differently colored sequentially flashing backlights is also provided.

Abstract: A display comprises: a single-view image display panel (6); and a parallax optic (8) disposed over a display face of the image display panel for restricting the angular spread of light output from the display face of the image display panel. This enables light to be concentrated in a desired viewing angle range (66), and avoids a user (56) seeing unwanted reflections that may occur as a result of a greater viewing angle range (64) if the parallax optic (8) is not provided. The display may be used, as an example, in a motor vehicle to prevent unwanted reflections from the windscreen (62) of the vehicle.

Abstract: An optical device comprises an input polarizer 4, a patterned retarder 5 and an output polarizer 12. The retarder 5 has regions 8 and 9, at least one of which alters the polarization of light from the input polarizer 4. The output polarizer 7 has a transmission axis 12 such that light passing through the regions 8 and 9 of the retarder 5 and through the output polarizer 7 is matched in amplitude, phase and polarization. Such a device may be used as a switchable parallax barrier with an LCD 2 to provide a display which is switchable between an autostereoscopic 3D mode and a 2D mode with the 2D mode having more uniform intensity across the display.

Abstract: A transflective liquid crystal display (70) comprises a liquid crystal cell (38) disposed between a front substrate (40) and a rear substrate (36), a front polariser (46) located in front of the front substrate (40) and a rear polariser (32) located behind the rear substrate (36), a front retarder (42, 44) located between the front substrate (40) and the front polariser (46), a rear retarder (62, 64) located between the rear substrate (36) and the rear polariser (32), and a light source (30) located behind the rear polariser (32). A transflective display having a number of differently coloured sequentially flashing backlights is also provided.

Abstract: A transflective liquid crystal display (70) comprises a liquid crystal cell (38) disposed between a front substrate (40) and a rear substrate (36), a front polariser (46) located in front of the front substrate (40) and a rear polariser (32) located behind the rear substrate (36), a front retarder (42, 44) located between the front substrate (40) and the front polariser (46), a rear retarder (62, 64) located between the rear substrate (36) and the rear polariser (32), and a light source (30) located behind the rear polariser (32). A transflective display having a number of differently coloured sequentially flashing backlights is also provided.

Abstract: A polarization rotator is provided for rotating the polarization direction of linearly polarized light by any arbitrary angle other than 90°. The device comprises a layer of liquid crystal material disposed between alignment surfaces. In one mode, a 90° twist is induced in the liquid crystal director. An expression is provided for relating the retardation of the layer to the amount of polarization rotation and the angle between the polarization direction of incident light and the alignment direction at the input side of the liquid crystal layer.

Abstract: A liquid crystal device such as a display comprises a twisted liquid crystal layer whose surface director orientation at a first surface is oriented in a first direction and whose surface director orientation at a second surface is oriented in a second different non-perpendicular direction. The layer is disposed, for instance, between a linear polarizer and a reflector. A retarder is disposed between the layer and the polarizer and compensates for residual retardation of the layer at a first voltage across the layer. For instance, the retarder has a retardation substantially equal to the residual retardation and an optic axis perpendicular to the bisectrix of the orientations.

Abstract: A reflective liquid crystal device comprises in sequence a linear polarizer, a retarder arrangement comprising two retarders, and a reflector. A first of the retarders provides a retardation of m&lgr;/2 and a second of the retarders provides a retardation of n&lgr;/4, where m is an integer and n is an odd integer, and wherein at least one of the first and second retarders comprises a Bistable Twisted Nematic (BTN) liquid crystal. This BTN retarder is switchable between a first state in which the retarder provides a retardation of m&lgr;/2 or n&lgr;/4 and a second state in which the retardation is zero.

Abstract: A broadband optical retardation device, such as may be used for polarisation encoding of display information or in diffractive optical systems, includes a patterned uniform half wave plate retarder in combination with a non-patterned uniform quarter wave plate retarder having an optic axis oriented at 90° to the xz plane. The patterned retarder consists of alternating first and second regions having first and second optic axes at different orientations to a reference axis, for example at +22.5° and −22.5° to the xz plane. Considering light of wavelength &lgr;° incident on the retarder and linearly polarised in the xy plane, such light is differently polarised by the regions, and the light output by the device includes regions in which the light is right circularly polarised and regions in which the light is left circularly polarised.

Abstract: A liquid crystal display device comprises: a layer of a chiral liquid crystal material disposed between first and second substrates; and means for applying a voltage across the liquid crystal layer. A first region of the liquid crystal layer is an active region for display and a second region of the liquid crystal layer is a nucleation region for generating a desired liquid crystal state in the first region when a voltage is applied across the liquid crystal layer. The ratio of the thickness d of the liquid crystal layer to the pitch p of the liquid crystal material has a first value (d/p)A in the first region of the liquid crystal layer and has a second value (d/p)N different from the first value in the second region of the liquid crystal layer.

Abstract: A polarisation rotator is provided for rotating the polarisation direction of linearly polarised light by any arbitrary angle other than 90°. The device comprises a layer of liquid crystal material disposed between alignment surfaces. In one mode, a 90° twist is induced in the liquid crystal director. An expression is provided for relating the retardation of the layer to the amount of polarisation rotation and the angle between the polarisation direction of incident light and the alignment direction at the input side of the liquid crystal layer.

Abstract: To improve switching times, especially at low temperatures, one or more reactive liquid crystalline compounds is added to a liquid crystal mixture used in an electroptical system. The electroptical system comprises a PDLC film comprising a liquid crystal mixture forming micro-droplets in an optically isotropic, transparent polymer matrix between 2 electrode layers. The liquid crystal mixture comprises one or more compounds of the formula I wherein R, A1, A2, Z1, Z2, X1, X2, Q, Y and n are as defined herein.

Abstract: To improve switching times, especially at low temperatures, one or more reactive liquid crystalline compounds is added to a liquid crystal mixture used in an electrooptical system. The electrooptical system comprises a PDLC film comprising a liquid crystal mixture forming micro- droplets in an optically isotropic, transparent polymer matrix between 2 electrode layers. The reactive liquid crystalline compounds are of formula II, R′—G′—R″, wherein R′, G′ and R″ are as defined herein. The liquid crystal mixture comprises one or more compounds of the formula I wherein R, A1, A2, Z1, Z2, X1, X2, Q, Y and n are as defined herein.

Abstract: A reflective liquid crystal device comprises a polarizer and a mirror between which are disposed several retarder. At least one of the retarders is a variable liquid crystal element whose optic axis is switchable so as to switch the device between a reflective state and a non-reflective state. In the non-reflective state, the total retardance of the retarders between the polariser and the mirror is equal to an odd number of quarter wavelengths for a wavelength at or adjacent the middle of the visible spectrum.

Abstract: To improve switching times, especially at low temperatures, one or more reactive liquid crystalline compounds is added to a liquid crystal mixture used in an electrooptical system. The electrooptical system comprises a PDLC film comprising a liquid crystal mixture forming micro- droplets in an optically isotropic, transparent polymer matrix between 2 electrode layers, one of the refractive indices of the liquid crystal mixture is matched to the refractive index of the polymer matrix, the PDLC film exhibits an electrically switching transparency essentially independent of the polarization of the incident light, the precursor of the PDLC film comprises one or more monomers, oligomers and/or prepolymers and a photoinitiator, and is cured photoradically, the liquid crystal mixture comprises one or more compounds of the formula I  wherein R, A1, A2, Z1, Z2, X1, X2, Q, Y and n are as defined herein.

Abstract: A liquid crystal device such as a display comprises a twisted liquid crystal layer whose surface director orientation at a first surface is oriented in a first direction and whose surface director orientation at a second surface is oriented in a second different non-perpendicular direction. The layer is disposed, for instance, between a linear polarizer and a reflector. A retarder is disposed between the layer and the polarizer and compensates for residual retardation of the layer at a first voltage across the layer. For instance, the retarder has a retardation substantially equal to the residual retardation and an optic axis perpendicular to the bisectrix of the orientations.