US Patent 7178949 Lighting equipment

The lighting device comprises a light source and an associated hollow reflector of transparent material having an internal surface and an external surface which are close to and far away from the source respectively. The inner surface of the reflector has in cross section at least one transverse plane passing through the source a discontinuous profile forming a plurality of adjacent steps each of which has a first face through which rays originating from the source can pass and a second face essentially parallel to the rays originating from the source. The outer surface of the reflector has a profile comprising one or more arcs of curves. The reflector is constructed and positioned in such a way that in the said transverse plane most of the rays emitted by the source are reflected through the first face of the steps on its inner surface and strike its outer surface undergoing total internal reflection and after passing back through the reflector emerge from it through the second faces of the steps on its inner surface undergoing a second refraction.