屈光度
Diopter \Di*op"ter\, Dioptra \Di*op"tra\, n. [L. dioptra, fr. Gr. ?. See 2d {Dioptric}.] An optical instrument, invented by Hipparchus, for taking altitudes, leveling, etc.
diopter n : a unit of measurement of the refractive power of a lens which is equal to the reciprocal of the focal length measured in meters