trifocal

trifocal
Having three foci. See t. lens.

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tri·fo·cal (')trī-'fō-kəl adj
1) having three focal lengths
2) of an eyeglass lens having one part that corrects for near vision, one for intermediate vision (as at arm's length), and one for distant vision
trifocal n
1) a trifocal glass or lens
2) trifocals pl eyeglasses with trifocal lenses

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tri·fo·cal (tri-foґ-) (triґfo-kəl) 1. having three foci. 2. containing one part for near vision, one for intermediate, and a third for distant vision; see under lens.

Medical dictionary. 2011.

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  • trifocal — ☆ trifocal [trī fō′kəl; ] also, and for n. usually [, trī′fō΄kəl ] adj. adjusted to three different focal lengths n. a lens like a bifocal but with an additional narrow area ground to adjust the intermediate focus for objects at c. 76 cm ( c. 30… …   English World dictionary

  • trifocal — I. adjective Date: 1826 having three focal lengths II. noun Date: 1899 1. plural eyeglasses with trifocal lenses 2. a trifocal glass or lens …   New Collegiate Dictionary

  • Trifocal — Trifocals are eyeglasses where the lenses have 3 regions to correct for distance, intermediate (arm s length), and near vision. They are mostly used by people with advanced presbyopia who have been prescribed 2 diopters or more of reading… …   Wikipedia

  • trifocal — /truy foh keuhl, truy foh /, adj. 1. Optics. having three foci. 2. (of an eyeglass lens) having three portions, one for near, one for intermediate, and one for far vision. n. 3. trifocals, eyeglasses with trifocal lenses. [1945 50; TRI + FOCAL] * …   Universalium

  • trifocal — adjective (of a pair of glasses) having lenses with three parts with different focal lengths. noun (trifocals) a pair of trifocal glasses …   English new terms dictionary

  • trifocal — tri•fo•cal [[t]traɪˈfoʊ kəl, ˈtraɪˌfoʊ [/t]] adj. 1) opt (of a lens) having three foci 2) (of an eyeglass lens) having three portions, one for near, one for intermediate, and one for far vision 3) trifocals, eyeglasses with trifocal lenses •… …   From formal English to slang

  • trifocal — adj. & n. adj. having three focuses, esp. of a lens with different focal lengths. n. (in pl.) trifocal spectacles …   Useful english dictionary

  • Trifocal tensor — In computer vision, the trifocal tensor can be considered as the generalization of the fundamental matrix in three views. It is a tensor thatincorporates all projective geometric relationships between three views andis independent of the scene… …   Wikipedia

  • trifocal glasses — glasses with trifocal lenses …   Medical dictionary

  • trifocal lens — a lens that has three segments with different refractive powers, ordinarily with the upper for distant, the middle for intermediate, and the lower for near vision; used in trifocal glasses …   Medical dictionary

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