diopter

Noun
Synonyms: dioptre

WordNet 3.0

Noun (1)

  1. a unit of measurement of the refractive power of a lens which is equal to the reciprocal of the focal length measured in meters; used by oculistsSynonyms: dioptre
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Webster's Dictionary (GCIDE)

Diopter \Di*op"ter\, Dioptra \Di*op"tra\, n. [L. dioptra, fr. Gr. ?. See 2d Dioptric.] An optical instrument, invented by Hipparchus, for taking altitudes, leveling, etc. [1913 Webster]
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