Patent ID: 6106128
Filing Date: 2000-08-22
Classification: G02B

Abstract:
An illumination system for distributing light rays from a light source, said illumination system comprising:a waveguide for propagating light rays from the light source and having a first refractive index that is greater than 1;a light extracting structure having a light extracting feature defined thereon for facilitating the egress of light rays directly from said solid waveguide through said light extracting structure, said light extracting feature, when viewed in cross-section, having a wide side and a narrow side, said wide side of said light extracting feature being located closer to said solid waveguide than said narrow side of said light extracting feature; andan interface for coupling said light extracting structure with approximately 100% contact to said solid waveguide, said interface having a second refractive index that is less than said first refractive index of said solid waveguide, wherein said second refractive index determines, at least in part, a cut-off angle for light output from said illumination system, said second refractive index being determined by the equation:n2.ltoreq.(n1.sup.2 -(cos(C)).sup.2).sup.1/2where n2 is said second refractive index, n1 is said first refractive index, and C is said cut-off angle of light output from said illumination system.