Dove prisms are shaped from a truncated right-angle prism. A beam of light entering one of the sloped faces of the prism undergoes total internal reflection from the inside of the longest (bottom) face and emerges from the opposite sloped face. Images passing through the prism are flipped, and because only one reflection takes place, the image's handedness is changed to the opposite sense. Dove prisms have an interesting property - when they are rotated along their longitudinal axis, the transmitted image rotates at twice the rate of the prism.
+/-30 arc min
Upon customers' request