Definitions
1.nounA 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.nounThe dioptre adjustment mechanism of a pair of binoculars.
3.nounAny lens system, such as a telescope.
4.nounA theodolite or similar surveyor’s angle measuring device.
5.nounAn alidade.
6.nounA surgical speculum.
7.nounAn instrument for drawing the skull by projections.