The illumination system (21) includes two radiation sources (23, 25) and an optical system for concentrating the radiation into beams, a common polarizing system (11) for splitting the beams (b.sub.I, b.sub.II) into linearly polarized sub-beams, and at least one polarization-rotating element (35). The...http://www.google.com.au/patents/US6018214?utm_source=gb-gplus-sharePatent US6018214 - Illumination system for an image projection device
