Total Internal Reflection (TIR) is a lossless reflection of a light ray from a surface as a consequence from the underlying physical principles, when the ray hits the surface between media coming from the optically denser side above a certain critical angle (see Fig. 1). This effect is used in collimator lenses; bulk optics that are able to capture the emission of a light source, e. g., the hemispherical radiation of an LED and gain control over it (see Fig. 2). They exhibit lens-like features at the entrance and the exit surface and sometimes additional micro-, or Fresnel lenses for further beam shaping possibilities. The third optical collimator surface in between most commonly makes use of the TIR phenomenon to ensure highly efficient ray deflection. The ray directions become more aligned in a specific direction, the ray divergence is reduced, so that the spherical wavefronts from the point source become flatter and close to plane waves. However, due to the presence of diffraction, a perfectly collimated beam cannot be created in reality, but very narrow spots with beam angles below 5° are possible.
A collimator has the advantage to protect the light source from the surroundings when designed accordingly. One such optic that is made from Suprax glass by Auer Lighting is the LED collimator Bern, which provides a spot light with 12° beam angle.