Roof Prism

Roof Prism It is a right-angle prism whose hypotenuse has been replaced by a 90o TIR roof. The 90o deviation applies only to rays, which are precisely normal to the entrance and exit faces, other rays being deflected by other amounts. They are ideal for use in spotting scopes, and any optical instrument where it is desirable to take an inverted image from an objective, turn it right side up, and bent it through a 90o angle, to maintain the correct visual orientation.