Diopter (disambiguation)

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