A lighting system includes a housing, a light-transmitting top member positioned across an open top of the housing, a light source positioned in the housing, a helical fiber biased between the light source and the top member, and an adjustment means for adjusting the compression of the helical fiber....http://www.google.es/patents/US7618175?utm_source=gb-gplus-sharePatente US7618175 - LED lighting system with helical fiber filament
