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Look up diopter in Wiktionary, the free dictionary.
In modern usage, diopter or dioptre is a measure of the refractive power of an optical system.
Diopter may also refer to:
- Historically, a dioptric lens
- Any lens system, such as a telescope
- A diopter sight
- A close-up lens used in photography
- A theodolite or similar surveyor's angle measuring device
- A dioptra, an old surveying device
- An alidade
- A surgical speculum
- An instrument for drawing the skull by projections