Nicol prism

plural Nicol prisms

1. engineeringAn optical device used to generate polarized light.

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   “You are in mortal danger,” declared their Scientific Officer, Dr. Counterfly, a scholarly sort, bearded and bundled like the rest of them, his eyes concealed by a pair of ingenious goggles, whose lenses proved to be matched pairs of Nicol prisms which could be rotated so as to control precisely the amount of light admitted to each eye.

   2006, Thomas Pynchon, Against the Day, Vintage, published 2007, page 155