dioptre
dioptre
[dʌɪˈɒptə]
(美 diopter)
noun
[dʌɪˈɒptə]
(美 diopter)
noun
- a unit of refractive power, which is equal to the reciprocal of the focal length (in metres) of a given lens
屈光度，折光度
- late 16th cent. (originally as diopter, denoting an alidade): from French, from Latin dioptra, from Greek, from di- 'through' + optos 'visible'. The term was used in the early 17th cent. to denote an ancient form of theodolite; the current sense dates from the late 19th cent
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