コーナーキューブプリズム

This prism has three mutually perpendicular intersected surface and a hypotenuse face. The three intersected surfaces are coated for high internal reflection. When light enters through the hypotenuse, it is reflected by each of the three surface in turn and emerges through the hypotenuse face parallel to the entering beam with a shift. The prism thus retro-reflects the beam to the source, regardless the orientation of the prism. It has a wider field of view. They are ideal in applications where orientation is difficult or impossible to control.

These is also an alternative form of the retro-reflector which consists of three perpendicular intersected mirrors in a holder. This is much lighter than the prism form but demands accurate assembly.