varifocaladj.
/ˌvɛːrɪˈfəʊkl/, U.S. /ˌvɛriˈfoʊk(ə)l/ a. Having a focal length that can be varied.
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1945 Jrnl. Soc. Motion Picture Engineers 45 466 A new positive Vari-Focal view-finder for motion picture cameras.
1962 Jrnl. Optical Soc. Amer. 52 353/2 The two-lens varifocal system consists of a single movable component placed behind a fixed component.
1967 Appl. Optics VI. 1085 (heading) Stereoscopic display using rapid varifocal mirror oscillations.
1979 Appl. Optics XVIII. 5/1 We have used a varifocal lens to compensate for changes in refractive index of lens elements with wavelengths from 190 nm to 600 nm.
b. Ophthalmology. = omnifocal adj. and n. at omni- comb. form . Also elliptical.
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the world > health and disease > healing > ophthalmology or optometry > aids to defective vision > [noun] > spectacles > lens of spectacles > types of
pebble1688
distance lens1907
omnifocal1962
toric1962
varifocal1975
1975 L. S. Sasieni Princ. & Pract. Optical Dispensing (ed. 3) xii. 373 Varifocal lenses have two areas of specified powers, for distance and reading, and an intemediate region in which the power gradually changes, from one to the other.
1982 Ophthalmic & Physiol. Optics II. 75 (heading) Theoretical aspects of concentric varifocal lenses.
1982 Ophthalmic & Physiol. Optics II. 75 Substantial amounts of unwanted astigmatism in the transition zone are intrinsic to the design and to other forms of concentric varifocal.
This entry has not yet been fully updated (first published 1986; most recently modified version published online December 2021).
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adj.1945