An LED light source is received in a groove portion provided in a light guide plate. The groove portion is covered with a base member, and the circumferential edge of the base member is bonded to the light guide plate. Concave portions or convex portions having desired shapes are provided in a surface...http://www.google.de/patents/US6889456?utm_source=gb-gplus-sharePatent US6889456 - Illumination apparatus
