US Patent 7695179 Illuminating device

An illuminating device has a light pipe that is elongate in shape and has a light-emitting face running in the direction of a longitudinal axis. A light-reflecting face is disposed opposite the light-emitting face, and the light-reflecting face has a plurality of prismatic cuts. Each prismatic cut includes a front face oriented at an angle B from a normal axis, the normal axis being 90 degrees from the longitudinal axis of the light pipe. The angle B is in the range of about 5 degrees to about 45 degrees and is such that it allows light to refract through at least one prismatic cut and then be internally reflected.