An optical navigation input device with a light guide which acts as a beam shaping element. The optical navigation input device includes a light source and the light guide. The light source emits a light beam having a substantially elliptical or substantially circular cross section. The light guide is positioned relative to the light source to receive the light beam from the light source in a first direction. The light guide also redirects the light beam in a second direction toward an illumination surface at a non-zero angle of incidence. The light guide directs the light beam through a refraction interface in order to illuminate a substantially circular area on the illumination surface.