diopter
noun
Forms diopters dioptra dioptre dioptry
- noun 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.
- noun The dioptre adjustment mechanism of a pair of binoculars or of a camera viewfinder.
- noun (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".
- noun (obsolete) Any lens system, such as a telescope.
- noun (obsolete) A theodolite or similar surveyor’s angle measuring device.
- noun (obsolete) An alidade.
- noun (obsolete) A surgical speculum.
- noun (obsolete) An instrument for drawing the skull by projections.
Synonyms
Etymology
From Latin dioptra, from Ancient Greek διόπτρα (dióptra).
Webster’s 1913
- noun An optical instrument, invented by Hipparchus, for taking altitudes, leveling, etc.
Etymology [L. dioptra, fr. Gr. Dioptric.]
Sources: Wiktionary · WordNet 3.0 · Webster’s 1913 — from the Wiktionary entry “diopter”, CC BY-SA 4.0. Details