Dove prism
Encyclopedia
A Dove prism is a type of reflective prism
Prism (optics)
In optics, a prism is a transparent optical element with flat, polished surfaces that refract light. The exact angles between the surfaces depend on the application. The traditional geometrical shape is that of a triangular prism with a triangular base and rectangular sides, and in colloquial use...

which is used to invert an image
Image
An image is an artifact, for example a two-dimensional picture, that has a similar appearance to some subject—usually a physical object or a person.-Characteristics:...

. Dove prisms are shaped from a truncated right-angle prism
Prism (geometry)
In geometry, a prism is a polyhedron with an n-sided polygonal base, a translated copy , and n other faces joining corresponding sides of the two bases. All cross-sections parallel to the base faces are the same. Prisms are named for their base, so a prism with a pentagonal base is called a...

. A beam of light entering one of the sloped faces of the prism undergoes total internal reflection
Total internal reflection
Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary and the incident angle is...

 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 is inverted but not laterally transposed.

Dove prisms have an interesting property that when they are rotated along their longitudinal axis, the transmitted image rotates at twice the rate of the prism. This property means they can rotate a beam of light by an arbitrary angle, making them useful in beam rotators, which have applications in fields such as interferometry
Interferometry
Interferometry refers to a family of techniques in which electromagnetic waves are superimposed in order to extract information about the waves. An instrument used to interfere waves is called an interferometer. Interferometry is an important investigative technique in the fields of astronomy,...

, astronomy
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...

, and pattern recognition
Pattern recognition
In machine learning, pattern recognition is the assignment of some sort of output value to a given input value , according to some specific algorithm. An example of pattern recognition is classification, which attempts to assign each input value to one of a given set of classes...

.

Lesso and Padgett (1999) and Moreno et al. (2003, 2004) found that there is a change in the state of polarization of a beam of light on passing through a rotated dove prism. The polarization-transforming properties of dove prisms are of particular interest because they can influence the signal measurement of the scientific instrument.
The Dove prism is named for its inventor, Heinrich Wilhelm Dove
Heinrich Wilhelm Dove
Heinrich Wilhelm Dove was a Prussian physicist and meteorologist. He was the father of Alfred and Richard Dove.-Early Years:...

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