Corner cube prism

A corner cube prism, also known as a retroreflector, a CCR, or a trihedral prism, is an optical prism  that sends an incoming beam

of light directly towards its point of origin while translating it spatially. It does this regardless of the angle of entry, which makes it 

very useful for applications in spectroscopy, satellites, or battlefield technology. Corner cube prisms are also used in land surveying, 

laser resonator cavities, electronic distance measurement, and space vessel docking.

Applications of corner cube prisms