Optical films

An optical film structure for backlit displays having two films, both in "prisms up" configuration. The first film, closer to the light guide, has an array of generally symmetric 90-degree prisms facing the viewer. The second film, farther from the light guide, has an array of generally asymmetric prisms facing the viewer, with one face of the prisms inclined at about 45 degrees and the other face generally perpendicular to the plane of the backlight. The prisms of the first and second films may have an azimuthal angle between them, and may have different pitches from each other. The film structure "recycles" a portion of the light from the light guide, thereby helping to increase uniformity over the area of the display. The film structure also "compresses" the light emerging from the light guide, thereby providing a more sharply peaked brightness distribution for the viewer.