Various embodiments involving structures and methods for illumination can be employed, for example, in projectors, head-mounted displays, helmet-mounted displays, back projection TVs, flat panel displays as well as other optical systems. Certain embodiments may include prism elements for illuminating,...http://www.google.co.uk/patents/US20050018309?utm_source=gb-gplus-sharePatent US20050018309 - Apparatus and methods for illuminating optical systems
