Patent ID: 10330843

Abstract:
An imaging directional backlight apparatus includes a waveguide and a light source array for providing large area directed illumination from localized light sources. The waveguide may include a stepped structure. The steps may 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, providing discrete illumination beams exiting from the top surface of the waveguide. Viewing windows are formed through imaging individual light sources and define the relative positions of system elements and ray paths. The uncorrected system creates non-illuminated void portions when viewed off-axis preventing uniform wide angle 2D illumination modes. The input end may have microstructures arranged to remove this non uniformity at wide angles. The microstructures may have reduced reflectivity for parts of the input end that contribute to stray light in privacy and autostereoscopic modes.