Pentagonal Prisms

Pentagonal prisms is one of the beam steering devices with fixed angle (90 °). It has two purposes: first, the outgoing light turns the incident light to a certain angle (90 °) regardless of the incident angle on the first side; Second, unlike a right angle prism, its image has neither rotation nor specular reflection. Pentaprism is commonly used in camera viewfinder, image observation system or measuring instrument.