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small optical instrument consisting of two similar telescopestelescope,
traditionally, a system of lenses, mirrors, or both, used to gather light from a distant object and form an image of it. Traditional optical telescopes, which are the subject of this article, also are used to magnify objects on earth and in astronomy; other types of
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 mounted on a single frame so that separate images enter each of the viewer's eyes. As with a single telescope, distant objects appear magnified, but the binocular has the additional advantage that it substantially increases the range of depth perception of the viewer because the magnified images are seen with both eyes. The frame of a binocular is usually hinged to permit adjustment of the distance between the telescopes. Focusing can be done by means of a wheel on the central axis between the telescopes; turning the wheel changes the distance from the objective lenses of the telescopes to the eyepieces. Separate focusing of each telescope from the eyepiece may be provided in some types of binocular. The term binocular now usually refers to the prism binocular, in which light entering each telescope through its objective lens is bent first one way and then the other by a pair of prisms before passing through one or more additional lenses in the eyepiece. The prisms aid in reducing the length of the instrument and in enhancing the viewer's depth perception by increasing the distance between the objective lenses. Other types of binocular include the opera glass and the field glass; both use Galilean telescopes, which do not employ prisms and which usually have less magnifying power than the telescopes in prism binoculars. A binocular is often specified by an expression such as "7×35" or "8×50"—the first number indicates how many times the binocular magnifies an object and the second number is the diameter of either objective lens in millimeters. The size of an objective lens is a measure of how much light it can gather for effective viewing.


See J. T. Kozak, Deep-Sky Objects for Binoculars (1988).


Of, pertaining to, or used by both eyes.
Of a type of visual perception which provides depth-of-field focus due to angular difference between the two retinal images.
Any optical instrument designed for use with both eyes to give enhanced views of distant objects, whose distinguishing performance feature is the depth perception obtainable.
References in periodicals archive ?
The patients' age, gender, AHP type, AHP degree ([degrees]), best corrected visual acuity, amount of deviation (prism diopters [PD]), ocular motility findings, and binocularity were recorded.
The principal focus of this article is on Jean Th[acute{e}]ophile Desaguliers (1683-1744), who carried out experiments on colour an d binocularity early in the century, and also made speculations about the mechanism of accommodation.
Bishop, president and chief executive officer of SOLA, stated, "With its full-width visual field and near perfect binocularity, AO PRO Easy offers wearers an exceptional balance of comfort and utility.
Laser blended vision, which is offered on certain laser platforms, is an enhanced form of monovision which controls the postoperative spherical aberration in order to increase depth of focus; this essentially enhances the intermediate vision in both the distance and near eye which aids binocularity and improves tolerance.
Tests for latent and manifest squint, binocularity and testing for near point of convergence as well as near point of accommodation were done and causes of eyestrain identified.
Postoperative binocularity in adults with longstanding strabismus.
Binocular attachments are available in relatively low powers to approximately 3x; single lens clip attachments are available in higher powers to approximately 7x where binocularity is not a priority (see Figure 6).
The association between nonstrabismic anisometropia, amblyopia, and subnormal binocularity.
26,27) Many of these newer approaches have, at their core, an attempt to develop binocularity.
This is important not just to optimise binocularity in anisometropia but also because of the need to encourage cortical use of the monocular input from each eye.
Post-natally, binocular connections develop in V1 (leading eventually to stereopsis), and this binocularity also allows nasal to temporal motion sensitivity to develop, which is relayed to the opposite MST via the corpus callosum.
However, this might also be related to the development of foveal tracking of objects moving in depth requiring the development of binocularity (see below).