image rotation prisms

From many kinds of prisms we can distinguish prisms that rotate input beam after few reflections inside. It means the output image is rotated about 180 degrees with respect to the input direction. The direction of the beam can be changed or unchanged.
Examples of image rotation prisms are:

  • ABBE-KOENIG prism, which is an image erector. It is set of prisms with roof faces for complete image reversal.
  • CORNER CUBE prism (Retroreflector; TRIHEDRAL prism). In the corner cube prism three reflecting surfaces are perpendicular each to the other (such as side walls of a cube). The input surface is perpendicular to the cube diagonal. Disregarding the angle of incidence the output beam is parallel to the input one, but it is of opposite direction. In set of several corner prisms, for better matching, their entrance – exit surface is often hexagonal. In case of this prisms the phenomenon of full internal reflection occurs so it is not necessary, (however it is possible) to put mirror coating on the reflecting faces.
  • DOVE prism (Image Rotator) – this prism rotates the image without changing the direction of input beam, which is parallel to the hypotenuse. Rotation of the prisms in relation to the subject causes double rotation of the image. DOVE prism should be used in a parallel beam.