US Patent 8727581 Optics for axially-transverse light emission

Apparatus, for illuminating a feature on a transparent light transmitting substrate or window, including an optical arrangement secured to one of the surfaces of the substrate for directing light into the substrate at an incident angle selected for propagation of light via total internal reflection (TIR) along the substrate. The optical arrangement has a rotationally symmetrical optic for surrounding a light source, a planar output surface, and an input surface divided into at least one curved zone bounded by a surface discontinuity, and at least one coupling material, with a refractive index greater than air, to optically and physically couple the output surface to the substrate.