Patent attributes
An imaging directional backlight apparatus including a waveguide, a light source array, for providing large area directed illumination from localized light sources. The waveguide may include a stepped structure, in which the steps may further include extraction features optically hidden to guided light, propagating in a first forward direction. Returning light propagating in a second backward direction may be refracted, diffracted, or reflected by the features to provide discrete illumination beams exiting from the top surface of the waveguide. A rear reflector is arranged to receive light transmitted by the features and to provide polarization recirculation. Viewing windows are formed through imaging individual light sources and hence defines the relative positions of system elements and ray paths. Retarder stack arrangements are provided to increase the efficiency of polarization recirculation, reduce the visibility to damage and to reduce color changes with viewing angle.
