Corner Cube Prism

Corner Cube prism has three mutually perpendicular surfaces and a hypotenuse face.  It operates on the principle of total internal reflectionTIR.  A beam entering the effective aperture is reflected by the three roof surfaces and emerges from the entrance/exit surface parallel to itself. This property is independent of direction of the retro-reflector, within acceptance angle limitations. 

For applications in which either the acceptance angle for TIR is exceeded, or the reflecting surfaces can not be kept sufficiently clean for TIR, a metal or dielectric coating can be applied to the reflecting surfaces.