High efficiency flat illuminator for liquid crystal micro-display

摘要

An illumination system for a flat panel micro-display device includes a flat panel edge lit lightguide having a polarizing layer on a major surface and a polarization rotator and reflector proximate to an edge face of the lightguide. The polarization rotator changes the polarization state of light that is initially reflected from the polarization layer to a desired polarization state from an undesired polarization state and the reflector reflects the light back to the polarization layer. The rotated and reflected light propagating within the lightguide passes though the polarizing layer and illuminates a LCD panel of the micro-display. The combination of the polarization rotator and the reflector provide a controlled system in which most of the initially reflected light is utilized to illuminate the LCD panel. In an embodiment, the polarizing layer is a polarizing film that passes P polarized incoming light and reflects S polarized incoming light, the polarization rotator is a quarter wave plate that rotates light by a quarter wave, and the reflector is a mirror that reflects light without changing the polarization state of the light.