Holographic optical elements (HOEs) can be used in systems and methods for providing illumination and for projecting images. The HOEs may be switchable HOEs, whose diffractive properties can be controlled. Described herein is a method of combining light from two or more illumination sources. In one embodiment,...http://www.google.ca/patents/US6211976?utm_source=gb-gplus-sharePatent US6211976 - Holographic projection system
