OPTICAL ELEMENT AND COLOR COMBINER

摘要

Optical elements, color combiners using the optical elements, and image projectors using the color combiners are described. The optical element includes light recycling stacks, a polarizing beam splitter, and a color-selective stacked retardation polarizing filter. The polarizing beam splitter includes a first reflective polarizer aligned to a first polarization direction. Each light recycling stack includes a second reflective polarizer aligned to the first polarization direction, and a retarder aligned at 45 degrees to the first polarization direction. The color combiner includes partially reflective light sources coupled to the optical element. Un-polarized light having different colors can enter the color combiner through the light recycling stacks, and combined light of a desired polarization state can exit the color combiner. Light having an undesired polarization state can be recycled to the desired polarization state within the color combiner, so that light utilization efficiency is increased. The image projector includes a color combiner coupled to an imaging source and projection elements, so that a first portion of the combined light is directed to the projection element, and a second portion of the combined light is recycled back into the color combiner.