Bauernfeind prism

A Bauernfeind prism is a type of reflecting prism used to deviate a beam of light by 45° to 60°, depending on its construction, while neither flipping nor rotating the image.

[1] It is named for its inventor, the German expert of geodesy Karl Maximilian von Bauernfeind.

Therefore, the prism requires a reflective coating for this surface to be usable in practice.

The Bauernfeind prism is commonly used in microscope tubes and in geodesy to deviate the path to the eyepiece in order make the device more ergonomic.

[5] More recent applications are glasses that deflect the viewing angle either downwards (for relaxed reading or watching TV[6]), or upwards (as in belay glasses for watching a climber while belaying).