Abbe prism

The Abbe prism , named after the German physicist Ernst Abbe , is a special dispersion prism that, like the Pellin-Broca prism, causes a constant beam deflection (60 °).

In a broader sense, the term Abbe prism denotes various prisms developed and used by Ernst Abbe . In addition to the dispersion prism, this includes the non-dispersive reflection prisms such as the Porro prism of the 2nd type and the Abbe-König prism, as well as their variants.

Structure and functionality

Beam path in a dispersive Abbe prism

The shape of the Abbe prism is a geometric prism with a right-angled triangle with interior angles of 30 °, 60 ° and 90 ° as its base . It is usually made of glass or some other transparent material. The light is usually radiated onto the shorter side surface and refracted into the prism. It then hits the second side of the cathetus , where it is totally reflected (assuming the appropriate choice of material that enables total reflection), and then exits the prism at the third edge.

The prism is designed for a defined wavelength of light and deflects it by exactly 60 ° from the original beam path. All other wavelengths are deflected by larger or smaller angles. The wavelength is selected by rotating the prism in the plane of the base and is non-linear to the angle of rotation due to the course of the dispersion.

To improve the optical properties, the Abbe prism can be composed of various individual prisms, for example two half prisms and a reflection prism . The use of more refractive materials (for the reflection prism), which enable total reflection in a larger spectral range, is advantageous here. The two half prisms made of lower refractive index material reduce the reflection losses. Due to the combination of several individual prisms, the basic shape no longer necessarily has to be a triangle. Therefore, other geometries can be found in the literature, which are referred to as Abbe prism.

Web links

• Abbe prism. In: Lexicon of Physics. Spektrum Akademischer Verlag, accessed on August 22, 2011 . 

Individual evidence

1. ↑ Heinz Haferkorn: Optics: Physico-technical basics and applications . Wiley-VCH, 2003, ISBN 978-3-527-40372-1 , pp. 388 .