Optical devices for guiding illumination are provided each having a body of optical material with staircase or acutely angled ramp structures on its top surface for distributing light inputted from one end of the device from the front exit faces of such structures along certain angular orientations,...http://www.google.se/patents/US20070189701?utm_source=gb-gplus-sharePatent US20070189701 - Optical devices for guiding illumination
