| 释义 |
diopter|daɪˈɒptə(r)|
Also in Lat. form dioptra.
[a. F. dioptre (1547 in Hatz.-Darm.), ad. L. dioptra, a. Gr. δίοπτρα an optical instrument for measuring heights, levelling, etc.; cf. also Gr. δίοπτρον spying-glass, f. δι-, δια- through + stem ὀπ- to see + instrumental suffix, -τρα, -τρον.]
1. An ancient form of theodolite, or instrument for taking angles.
1613M. Ridley Magn. Bodies 112 Make a hole as in a Diopter, that the Sunne may shine in at it. 1641W. Gascoigne in Rigaud Corr. Sci. Men (1841) I. 51 Two dioptraes..fitted with glasses, hair, and moveable rims. 1851Otté tr. Humboldt's Cosmos III. 53 Long tubes..employed by Arabian astronomers.. to the extremities of which ocular and object diopters were attached. 1857Whewell Hist. Induct. Sc. I. 354 He wrote..a treatise on the Dioptra..an instrument for taking angles.
2. The index-arm of a graduated circle; = alidad.
1594Blundevil Exerc. iv. xx. (ed. 7) 476 Having set the Diopter of your Astrolabe at that Altitude. 1662J. Davies tr. Olearius' Voy. Ambass. 192, I took the Horizon with my Astrolabe, and having put my Dioptra into it, I turn'd my self towards the Sea..and could easily discern it. 1874Knight Dict. Mech. I. 172/1 To measure an angle with the astrolabe, the latter is placed with its center over the vertex of the angle, and turned until the fixed diopters sight in the direction of one side. The movable strip with its diopters is then sighted in the direction of the other side, and the angle contained between the two strips is read off.
†3. A surgical speculum. Obs.
1706Phillips (ed. Kersey), Dioptra..a Surgeon's Instrument. 1727–51Chambers Cycl., Dioptra, among surgeons, denotes an instrument whereby to dilate the matrix, or anus, and inspect any ulcers therein; called also speculum matricis, and dilatatorium. 1872Thomas Dis. Women 37 If therefore, says Paul of ægina, the ulceration be within reach, it is detected by the dioptra.
4. An instrument for obtaining drawings of the skull by projections.
1878Bartley tr. Topinard's Anthrop. ii. iii. 269.
5. A unit of measurement for lenses; = dioptric n. 2.
Usu. spelt dioptre in the U.K.
1890Gould New Med. Dict. 133/1 Diopter or Dioptric. |