A light guide with optics accurately controls the light exiting the guide. The device achieves accurate control of the reflected light by extracting light from a limited area of the light guide. The configuration of the reflectors used for the selective extraction determines the nature of the output...http://www.google.com.hk/patents/US8152352?utm_source=gb-gplus-share專利 US8152352 - Optic system for light guide with controlled output
