pentaprism

or pen·ta prism

[ pen-tuh-priz-uh m ]
/ ˈpɛn təˌprɪz əm /

noun

a prism that has five faces, a pair of which are at 90° to each other; a ray entering one of the pair emerges from the other at an angle of 90° to its original direction: used especially in single-lens reflex cameras to reverse images laterally and reflect them to the viewfinder.

Origin of pentaprism

First recorded in 1935–40; penta- + prism

British Dictionary definitions for pentaprism

pentaprism
/ (ˈpɛntəˌprɪzəm) /

noun

a five-sided prism that deviates light from any direction through an angle of 90°, typically used in single-lens reflex cameras between lens and viewfinder to present the image the right way round