An optical illumination system comprising a waveguide that accepts light generated by a diffuse light source and transmits the light via total internal reflection. Attached on one face of the waveguide is an array of microprisms, with each microprism having an light input surface parallel to a light...http://www.google.com.au/patents/US5555109?utm_source=gb-gplus-sharePatent US5555109 - Illumination system employing an array of microprisms
