A Dove prism is a type of reflective

prism PRISM is a code name for a program under which the United States National Security Agency (NSA) collects internet communications from various U.S. internet companies. The program is also known by the SIGAD . PRISM collects stored internet ...

which is used to invert an

image An image or picture is a visual representation. An image can be Two-dimensional space, two-dimensional, such as a drawing, painting, or photograph, or Three-dimensional space, three-dimensional, such as a carving or sculpture. Images may be di ...

. Dove prisms are shaped from a truncated right-angle

. The Dove prism is named for its inventor,

Heinrich Wilhelm Dove Heinrich Wilhelm Dove (6 October 1803 – 4 April 1879) was a Prussian physicist and meteorologist. Early years Dove was born in Liegnitz in the Kingdom of Prussia. Dove studied history, philosophy, and the natural sciences at the University o ...

. Although the shape of this prism is similar to the shape described by a

dovetail joint A dovetail joint or simply dovetail is a joinery technique most commonly used in woodworking joinery (carpentry), including furniture, cabinets, log buildings, and traditional timber framing. Noted for its resistance to being pulled apart, a ...

, the etymology of the two is unrelated. A beam of light travelling parallel to the longitudinal axis, entering one of the sloped faces of the prism, undergoes

total internal reflection In physics, total internal reflection (TIR) is the phenomenon in which waves arriving at the interface (boundary) from one medium to another (e.g., from water to air) are not refracted into the second ("external") medium, but completely refl ...

from the inside of the longest (bottom) face and emerges from the opposite sloped face. Images passing through the prism are flipped (mirrored), and because only one reflection takes place, the image is also inverted but not laterally transposed.

Refraction In physics, refraction is the redirection of a wave as it passes from one transmission medium, medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commo ...

at the entrance and exit surfaces results in substantial image

astigmatism Astigmatism is a type of refractive error due to rotational asymmetry in the eye's refractive power. The lens and cornea of an eye without astigmatism are nearly spherical, with only a single radius of curvature, and any refractive errors ...

when used in convergent light. Thus the Dove prism is used almost exclusively for images appearing at infinity. If the flat

hypotenuse In geometry, a hypotenuse is the side of a right triangle opposite to the right angle. It is the longest side of any such triangle; the two other shorter sides of such a triangle are called '' catheti'' or ''legs''. Every rectangle can be divided ...

surface of a Dove prism is cut into a roof shape, the result is an

Amici roof prism An Amici roof prism, named for its inventor, the Italian astronomer Giovanni Battista Amici, is a type of reflecting prism (optics), prism used to deviate a beam of light by 90° while simultaneously inverting the image. It is commonly used in t ...

Rotation

A reflection in one axis of a plane is always

equivalent Equivalence or Equivalent may refer to: Arts and entertainment *Album-equivalent unit, a measurement unit in the music industry *Equivalence class (music) *'' Equivalent VIII'', or ''The Bricks'', a minimalist sculpture by Carl Andre *'' Equiva ...

to a reflection and rotation in two other axes (with the angle between the source and image being twice the angle between the source and reflection axis of the prism). Thus, Dove prisms can be used to create ''beam rotators'', which have applications in fields such as

interferometry Interferometry is a technique which uses the ''interference (wave propagation), interference'' of Superposition principle, superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important inves ...

astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...

, and

pattern recognition Pattern recognition is the task of assigning a class to an observation based on patterns extracted from data. While similar, pattern recognition (PR) is not to be confused with pattern machines (PM) which may possess PR capabilities but their p ...

. Lesso and Padgett (1999) and Moreno et al. (2003, 2004) found that there is a change in the state of

polarization Polarization or polarisation may refer to: Mathematics *Polarization of an Abelian variety, in the mathematics of complex manifolds *Polarization of an algebraic form, a technique for expressing a homogeneous polynomial in a simpler fashion by ...

of a beam of light on passing through a rotated dove prism. Polarization rotation in the infrared has been known for much longer (Johnston 1977). The polarization-transforming properties of dove prisms are of particular interest because they can influence the signal measurement of the scientific instrument.

References

* * * *{{cite journal , first = L. H. , last = Johnston , year = 1977, title = Broadband polarization rotator for the infrared , journal = Applied Optics , volume = 16 , issue = 4 , pages = 1082–4 , doi = 10.1364/AO.16.001082 , pmid = 20168639 , bibcode = 1977ApOpt..16.1082J Prisms (optics)

Rotation

See also

References