right angle prisms
Right-angle prism is a glass block in shape of pentahedron with two non-active triangular surfaces and other 3 optically active surfaces. These prisms operate as reflectors and most often are used as mirrors to deflect the light beam. Depending on the input surface the image can be shifted by 90 degrees (hypotenuse is mirror coated) or 180 degrees in Porro type (short faces are mirror coated). It is also possible to utilize full internal reflection in place of mirror coating. Prisms offer a significant upside when compared to typical mirrors because they offer greater resistance to mechanical load and external stress. This makes them easier to mount and operate in applications with harsh conditions, making them a perfect substitute as reflectors.