diopter

Meaning

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.
• The dioptre adjustment mechanism of a pair of binoculars or of a camera viewfinder.
• 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".
• Any lens system, such as a telescope.
• A theodolite or similar surveyor’s angle measuring device.
• An alidade.
• A surgical speculum.
• An instrument for drawing the skull by projections.

Origin

• From Latin dioptra, from Ancient Greek διόπτρα.