Patent ID: 8259068

Claim:
An optical navigation input device comprising: a light source to emit a light beam having a substantially elliptical or substantially circular cross section; and a light guide positioned relative to the light source to receive the light beam from the light source in a first direction and to redirect the light beam in a second direction toward an illumination surface at a non-zero angle of incidence, wherein the light guide is configured to direct the light beam through a refraction interface configured to illuminate a substantially circular area on the illumination surface, wherein the light guide comprises: a light input interface to receive the light beam from the light source; and a reflection surface to internally reflect the light beam according to total internal reflection (TIR) toward the refraction interface, wherein the reflection surface comprises a first planar surface at a first angle, q tir , relative to a surface normal of the illumination surface; wherein the refraction interface comprises a second planar surface at a second angle, q tlt , relative to the surface normal of the illumination surface; wherein the first angle, q tir , of the reflection surface is between about 22 to 30 degrees, and the second angle, q tlt , of the refraction interface is between about 23 to 3 degrees.