Retroreflectors are trihedral prisms, Commonly referred to as corner cubes, the prisms most sold available in three different sizes (Ø10.0 mm, Ø25.4 mm, or Ø50.0 mm). Retroreflectors reflect an image or beam back toward its original direction via three total internal reflections (TIR). The beam or image will be inverted and reflected through 180° even if the angle of incidence is not zero. The insensitivity of the alignment of the prism makes it an ideal retroreflecting optic. For these retroreflecting prisms, the incident and reflected beams will be parallel to within 2 arc sec to 6 arc min as required. However, unless the incident and reflected beams strike the exact center of the optic, they will not overlap but rather be shifted with respect to each other. For example, if the incident beam strikes the optic 3 mm to the right of center, the retroreflected beam will emerge 3 mm to the left of center.
Additionally, the retroreflected beam will experience a change in its polarization state when propagated through a solid retroreflector.
These prisms are fabricated from N-BK7, UV fused silica, Ge etc
They can be AR coated on the incidence face and metal coated with black painting on the three reflective faces.