90° prisms, Brewster prisms, and other special shapes.
Prisms are optical elements with plane surfaces that are not arranged parallel to each other.
There are reflection and dispersion prisms. In reflection prisms, the effect of total reflection is used to deflect beams or rotate images. Dispersion prisms, in contrast, are used to disperse or spectrally separate light.
Right-angled Prism
Depending on the incidence of the beam, right-angled prisms are used to deflect a collimated beam by 90° or 180°.
Thanks to the total reflection, very high reflection values are achieved. These prisms can serve as broadband mirrors with a high reflection.
Dove Prism
Dove prisms are almost exclusively used in parallel light. They are used like right-angled prisms and are especially popular when a large distance between incoming and outgoing beams should be achieved. Additionally, these prisms are also used to rotate an image.
Penta Prism
Penta prisms are used to deflect beams by 90° without affecting the orientation of the image. These prisms are often used in rangefinders.
Retroreflector
The reflection of an incident beam occurs in retroreflectors on three surfaces, each perpendicular to the other.
The so-called cat’s eyes are used to deflect beams by 180° whereas the outgoing beam is always parallel to the incident beam. Because of their properties, these optics are preferred for optical adjustments.
Isosceles Brewster Prism
Isosceles Brewster prisms are mostly used to deflect beams. The apex angle is selected such that incident and outgoing beams lie at the Brewster angle in order to transmit without any loss. These prisms, therefore, do not require an AR coating.
Equilateral Prism
Equilateral prisms are used in spectral separation. Not only can white light be divided into the spectral colours, laser beams of different wavelengths can also be separated.
Anamorphic Pair of Prisms
By using a pair of prisms, elliptical beam cross-sections can be converted to round cross-sections. Here the fact that beam deflection only occurs in one direction – toward the short side of the elliptical beam profile – is taken advantage of.