Definition of diopter in English:

diopter

Syllabification: di·op·ter
Pronunciation: /dīˈäptər
 
/

noun

A unit of refractive power that is equal to the reciprocal of the focal length (in meters) of a given lens.
More example sentences
  • The focusing power of a lens is measured in dioptres.
  • Refractive error is measured in dioptres, and myopia is designated with a minus sign.
  • The difference between the focusing powers of these two axes, measured in dioptres, is the astigmatism.

Origin

late 16th century (originally denoting an alidade): from French, from Latin dioptra, from Greek, from di- 'through' + optos 'visible'. The term was used in the early 17th century to denote an ancient form of theodolite; the current sense dates from the late 19th century.

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