Dioptre vs. Diopter

Dioptrenoun

A unit employed by oculists in numbering glasses according to the metric system; a refractive power equal to that of a glass whose principal focal distance is one meter.

Dioptre

A dioptre (British spelling) or diopter (American spelling) is a unit of measurement of the optical power of a lens or curved mirror, which is equal to the reciprocal of the focal length measured in metres. (1 dioptre = 1 m−1.) It is thus a unit of reciprocal length.

Diopternoun

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.

Diopternoun

The dioptre adjustment mechanism of a pair of binoculars or of a camera viewfinder.

Diopternoun

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".

Diopternoun

(obsolete) Any lens system, such as a telescope.

Diopternoun

(obsolete) A theodolite or similar surveyor’s angle measuring device.

Diopternoun

(obsolete) An alidade.

Diopternoun

(obsolete) A surgical speculum.

Diopternoun

(obsolete) An instrument for drawing the skull by projections.

Diopternoun

An optical instrument, invented by Hipparchus, for taking altitudes, leveling, etc.

Diopternoun

a unit of measurement of the refractive power of a lens which is equal to the reciprocal of the focal length measured in meters