The Dove prism is made from a truncated right-angled prism. When a beam impinges upon one sloped face, such that the beam is parallel to the longest face, at this sloped face the beam is refracted such that it strikes the longest face at a angle that the beam is TIR reflected. Following this reflection the beam is refracted out of the prism by the second sloped face. The beam is parallel and coincident with the input beam but the image is inverted. A feature of this prism is that when the Dove is rotated about the long axis the output image is rotated at twice the rotation speed. This means that the prism can rotate the image by any arbitrary angle and therefore they are useful as beam rotators in interferometry, astronomy, and image recognition. The prism is also used for the rotation of the polarization state of the beam.