High Efficiency Diffractive Incouplers for Light Guides

摘要

High efficiency diffractive light incouplers for light guides are described. We show that it is possible to couple white LED light into light guide with good white balance and high incoupling efficiency by using binary radial grating structures. Furthermore, a double-sided perpendicularly oriented grating configuration at opposite sides of a thin light guide is shown to provide significantly higher overall efficiency than one sided grating. This is a configuration that can be used in many mobile backlighting applications. In addition, a double grooved binary grating is introduced which can produce theoretically up to 100% incoupling efficiencies by using monochromatic light sources. This high efficiency is comparable to the slanted gratings. Replication techniques and incoupling efficiency simulations for slanted gratings are introduced by using a high refractive index material (n=1.71@525 nm).