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.
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.