A ring-shaped light emitting unit comprising a ring-shaped light guiding member having a light emitting surface which continues in a direction in which the ring-shaped light guiding unit extends, and a light guiding path for introducing light of a light source into the ring-shaped light guiding member...http://www.google.fr/patents/US7147356?utm_source=gb-gplus-shareBrevet US7147356 - Ring-shaped light emitting unit
