diopter

See also: Diopter

English

Alternative forms

Etymology

From Latin dioptra, from Ancient Greek διόπτρα (dióptra).[1]

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(Can this(+) etymology be sourced?)

Noun

diopter (plural diopters)

  1. A unit of measure of the power of a lens or mirror, equal to the reciprocal of its focal length in meters. Myopia is diagnosed and measured in diopters.
  2. The dioptre adjustment mechanism of a pair of binoculars or of a camera viewfinder.
  3. (photography, dated) A lens element attached to the front of a photographic lens to shorten the lens's minimum focus distance; also called a "close-up filter".
  4. (obsolete) Any lens system, such as a telescope.
  5. (obsolete) A theodolite or similar surveyor’s angle measuring device.
  6. (obsolete) An alidade.
  7. (obsolete) A surgical speculum.
  8. (obsolete) An instrument for drawing the skull by projections.

Translations
alidade — see alidade
speculum — see speculum

References
  1. Oxford Dictionaries

Anagrams
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