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User:Paul_Pot

Schematic drawing of a binocular with porro-prisms

Reflective prisms are a type of prisms in which a light beam traveling through the prism is reflected on at least one surface in the prism. The reflection can be either through total internal reflection or a mirrorized surface, with total internal reflection minimizing reflection losses.

A typical usage for reflective prisms is to erect the image in optical systems such as binoculars or single-lens reflex cameras – without the prisms the image would be upside down for the user.

Depending on the number of reflective surfaces, their location to each other and to the beam a reflective prism does one or more of the following: It flips, inverts, rotates, deviates or displaces the beam traveling through it. Furthermore some reflective prisms change the handedness of the beam. With the dove prism being the notable exception, reflective prism are usually constructed so that the beam enters and leaves the prism at an 90° angle in order to avoid the dispersion of light. This is in contrast to dispersive prisms which are used to break light up into its constituent spectral colors – dispersive prisms usually work without reflection on an face of the prism. Another type of prism that does not take advantage of reflections are deflecting prisms (such as wedge prisms), which are used to deflect or shape a beam of light for applications such as beam steering^[1] and beam shaping^[2].

Types of Reflective prisms

Simple reflective prism

The simplest reflective prism makes use of one reflection. It

Porro prism

Double porro prism

Lore ipsum

Double Porro prisms are commonly used in binoculars as an image erecting system.

Porro–Abbe prism

Porro-Abbe prism

Instead of a double Porro prism, sometimes Porro-Abbe prims are used in "Porro" type binoculars as an image erecting system.

Amici roof prism

The Amici prism is the simplest type of roof prism. This prism typically utilizes total internal reflection to deviate a beam of light by 90° while simultaneously inverting the image. The handedness of the image is unchanged and no deviation is introduced.

The roof faces of the prism are sometimes coated to provide mirror surfaces. This allows the prism to be constructed with other beam deviate angles besides 90° without being limited by total internal reflection.

It is commonly used in the eyepieces of telescopes as an image erecting system.

Pentaprism

Roof pentaprism

A typical pentaprism deviates a beam by 90°, and neither invertes nor reverses the image.^[3]

A roof-pentaprism has replaced one reflective surface with a roof section in order to flip the image horizontally. Roof pentaprisms are commonly used in single-lens reflex cameras as an image erecting system for the view-finder, with the reflex-mirror flipping the image vertically and the roof-pentaprism flipping the image horizontally.

Schmidt–Pechan prism

Schmidt-Pechan prisms are used in "roof" type binoculars as an image erecting system.

Abbe–Koenig prism

Instead of Schmidt-Pechan prisms, sometimes Abbe-Koenig prims are used in "roof" type binoculars as an image erecting system.

Bauernfeind prism

Retroreflector prism

Dove prism

Usages

Overview of reflective prisms
Fernglas Dialyt von
M. Hensoldt & Söhne in Wetzlar (1905) mit Dachkant-Pentaprisma mit dritter reflektierender Fläche
Geradsichtiges Fernglas von Hensoldt (1905) mit Abbe-König-Prisma

References

[1] ttp://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=147

[2] ttp://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=149

[3] ttp://www.newport.com/Penta-Prisms/141105/1033/info.aspx

[1]

[2]

[3]

User:Paul Pot/Reflective prism

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