The unit of refracting power of lenses, denoting the reciprocal of the focal length expressed in meters. [G. dioptra, a leveling instrument]
- prism d. (p.d.) the unit of measurement of the deviation of light in passing through a prism, being a deflection of 1 cm at a distance of 1 m.
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di·op·ter or chiefly Brit di·op·tre dī-'äp-tər, 'dī-.äp- n a unit of measurement of the refractive power of a lens equal to the reciprocal of the focal length in meters
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di·op·ter (di-opґtər) [Gr. dioptra optical instrument for measuring angles] a unit of refractive power of lenses: the reciprocal of the focal length in meters is the refractive power in diopters. Symbol D.Medical dictionary. 2011.