Definition of "diopter" in Anglais

noun

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.