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A Schmidt–Pechan prism is a type of optical prism used to rotate an image by 180°. These prisms are commonly used in binoculars as an image erecting system. The Schmidt–Pechan prism makes use of a roof prism section (from the German: "Dachkante", lit. roof edge ).
Abbe-Koenig prisms are significantly longer than Schmidt–Pechan prisms, and were and are rarely used except in large roof prism type binoculars, where light weight, compact size and cost are less important than ultimate light-gathering power.
The distinction between a roof prism and a Porro prism is that for the roof prism the roof edge lies in the same plane as entrance and exit beam, while for a Porro prism the (left out) roof edge is orthogonal to the plane formed by the beams.
Binoculars using either a Schmidt–Pechan roof prism, Abbe–Koenig roof prism or an Uppendahl roof prism benefit from phase coatings that compensate for a loss of resolution and contrast caused by the interference effects that occur in untreated roof prisms.
A roof prism, also called a Dachkanten prism or Dach prism (from German: Dachkante, lit. "roof edge"), is a reflective prism containing a section where two faces meet at a 90° angle, resembling the roof of a building and thus the name. Reflection from the two 90° faces returns an image that is flipped laterally across the axis where the faces ...
BAK-4 barium crown glass (glass code 569560) has a higher index of refraction than BK7, and is used for prisms in high-end binoculars. In that application, it gives better image quality and a round exit pupil. An achromatic doublet, which combines crown glass and flint glass.
An Amici roof prism, named for its inventor, the Italian astronomer Giovanni Battista Amici, is a type of reflecting prism used to deviate a beam of light by 90° while simultaneously inverting the image. It is commonly used in the eyepieces of telescopes as an image erecting system.
With short-focal length instruments, a mirror diagonal is preferred over a prism. Prism diagonals. A prism diagonal uses a simple 90°-angle prism, pentaprism, or an Amici roof prism rather than a mirror to bend the optical path.
A Perger prism or Perger–Porro prism system is a prism, that is used to invert (rotate by 180°) an image. The special feature of this prism is that, like a traditional double Porro prism system, it manages this with only four beam deflections and has neither a roof edge with the accompanying phase correction problems, a mirrored surface or ...
Dielectric phase-correction prism coatings are applied in a vacuum chamber with maybe 30 different superimposed vapor coating layers deposits, making it a complex production process. In a roof prism without a phase-correcting coating, s-polarized and p-polarized light each acquire a different geometric phase as