Abstract: A liquid crystal cell (5) comprises a layer (4) of cholesteric liquid crystal material; and a retarder (3) disposed in an optical path through the layer (4) of cholesteric liquid crystal material. The cholesteric liquid crystal material is switchable between a first state in which it cooperates with the retarder (3) to provide a first viewing angle range and a second state in which it cooperates with the retarder (3) to provide a second viewing angle range which is smaller than the first viewing angle range. The pitch of the cholesteric liquid crystal material is greater than an intended wavelength of operation of the liquid crystal cell divided by the average refractive index of the liquid crystal material. The liquid crystal cell may be used as a Viewing Angle Restriction (VAR) element, to enable another component, such as a display panel (6), to be operated in either a wide viewing mode or a narrow viewing mode.

Abstract: A display is provided for switching between a narrow or private viewing mode and a wide or public viewing mode. The display comprises a display device which is controlled to provide display of a desired image or sequence of images. This is associated with a liquid crystal device having at least one liquid crystal layer whose molecules are switchable between a first state providing a first angular viewing range and a second state providing a second angular viewing range which is within and smaller than the first angular viewing range. With the molecules in the second state, the device at least partially blocks light propagating towards part of the first angular viewing range outside the second angular viewing range. The or each liquid crystal layer is in contact with at least one alignment surface, the or each of which comprises a uniform non-patterned alignment surface.

Abstract: A liquid crystal cell (5) comprises a layer (4) of cholesteric liquid crystal material; and a retarder (3) disposed in an optical path through the layer (4) of cholesteric liquid crystal material. The cholesteric liquid crystal material is switchable between a first state in which it cooperates with the retarder (3) to provide a first viewing angle range and a second state in which it cooperates with the retarder (3) to provide a second viewing angle range which is smaller than the first viewing angle range. The pitch of the cholesteric liquid crystal material is greater than an intended wavelength of operation of the liquid crystal cell divided by the average refractive index of the liquid crystal material. The liquid crystal cell may be used as a Viewing Angle Restriction (VAR) element, to enable another component, such as a display panel (6), to be operated in either a wide viewing mode or a narrow viewing mode.

Abstract: An illumination system (32) is provided for producing output light having a variable angular illumination range for illuminating a display panel (31) in a display device (30). The illumination system (32) comprises first and second light sources (34 and 36) and is operable selectively in a first mode in which the output light comprises light derived from the first light source (34) with substantially no light derived from the second light source (36), and in a second mode in which the output light comprises light derived from at least the second light source (36). The output light derived from the first light source (34) has a first angular illumination range and the output light derived from the second light source (36) has a second angular illumination range wider than the first angular illumination range. The first mode can be used as a private mode and the second mode can be used as a public mode.

Abstract: A display is provided for providing a restricted viewing mode, for example a private viewing mode where the display may be viewed from a limited region of space by a single viewer and not by other people outside the viewing region. The display comprises a source of polarised light and an output polariser. Between these are provided a controllable pixellated spatial polarisation modulating layer, for example of the liquid crystal type. Also, a polarisation modifying layer is provided between the polarisers and is spaced from the modulating layer. The modifying later comprises a plurality of sets of regions with the regions of each set having the same polarisation modifying effect and the regions of different sets having different polarisation modifying effects. The light path between the modulating layer and the modifying layer is polariser-free.

Abstract: A method is provided that allows simultaneous control of macroscopic azimuthal and zenithal liquid crystal alignment (?, ?) across a liquid crystal layer by controlling the area ratios between first, second and third different types of alignment region (T1, T2, T3) in a patterned alignment layer, the three different types of alignment region (T1, T2, T3) tending to induce liquid crystal alignment in the liquid crystal layer in three different respective, non-coplanar, principal orientations (z, x, y). In the illustrated example, the first type of alignment region (T1) tends to induce substantially homeotropic alignment (in the z direction) and the second and third types of alignment region (T2, T3) tend to induce substantially planar alignment in different, orthogonal, principal orientations (in the x and y directions).

Abstract: An OCB device comprises upper and lower substrates, each provided with an alignment layer. A liquid crystal layer is provided between the substrates. The lower substrate has a low pre-tilt in regions A and C, so that an H-state is stable in these regions when no voltage is applied across the liquid crystal layer. Region B has a high pre-tilt on the lower substrate, so that a HAN state is stable in region B under zero applied voltage. When a voltage is applied across the liquid crystal lever, a V-state is formed at the interface between the HAN-state and the H-states. This V-state then displaces the H-states in regions A and C. The high pre-tilt region, region B, is acting as a nucleation region. The V-state forms at a lower applied voltage than if the nucleation region is not provided.