Penta-prism

pentaprism

[pen-tuh-priz-uhm]
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.
Also, penta prism.


Origin:
1935–40; penta- + prism

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World English Dictionary
pentaprism (ˈpɛntəˌprɪzəm)
 
n
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

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