Abstract: An optical device such as an overlay panel for a LCD display, comprises an element of light-transmitting material having a surface configured to form a stepped Fresnel prismatic structure. The light-transmitting material itself or ribbed light refracting element, said element incorporates an array of graded refractive index features adapted to impart light dispersing of diffusing characteristics to the light-transmitting material. In an alternative arrangement, the element of light-transmitting material has a layer configured to form a stepped Fresnel-type surface and an additional layer incorporating such an array of graded refractive index features.

Abstract: A light diffusing screen is made by exposing a photopolymerisable material to polymerising light through a mask having an array of light-transmitting apertures in an opaque background or vice versa, at least some of the light being directed obliquely onto the photopolymerisable material. The resulting photopolymerised material has asymmetric light diffusing properties. In some embodiments two beams of light directed onto the photopolymerisable material are equally and oppositely inclined to the perpendicular to the plane of the material. An analogous effect may be provided, in other embodiments, by exposing the photopolymerisable material to light converging conically on the photopolymerisable material.

Abstract: Screens having unique optical properties are produced according to the invention by crosslinking and stretching, or otherwise deforming, a sheet of light-diffusing material having symmetrical light diffusion characteristics under conditions sufficient to induce asymmetry. Screens made from the asymmetric light diffusing materials described herein exhibit enhanced brightness and clarity. Utilizing the present methods, optical materials having a desired view angle or improved optical characteristics can be achieved.

Abstract: In the manufacture of a screen suitable for use as a rear projection screen, a first layer (10) of a photopolymerisable monomer or oligomer which is tacky in its monomeric or oligomeric form and non-tacky in its polymerised form, is exposed to polymerising light, such as ultra-violet light, in a pattern comprising an array of spots of such light, and consequent selective polymerisation is allowed to take place in the first layer (10). There is then applied to the exposed surface of the first layer (10) a printing medium comprising an opaque pigment layer (28) on a supporting substrate (30) so that the pigment layer (28) contacts the exposed surface of the first layer (10) and sticks to the unpolymerised and therefore still tacky regions of the first layer (10), but not to the polymerised regions. The substrate (30) carrying the pigment layer (28) is then stripped from the first layer (10), leaving pigment (28) adhering only to the unpolymerised regions.

Abstract: Various forms of light-diffusing screen are disclosed comprising plastics sheets having surface texturing of some kind, adding to or modifying the diffusing effect. The plastics sheets may have bulk diffusing characteristics in addition to the surface texturing. The surface texturing may be produced by, for example, embossing or by molding the plastics against a textured surface such as a "brushed" surface or a ribbed or grooved surface imparting asymmetrical diffusion characteristics to the screen.