binocular

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Related to binocularly: monocular, binoculars

binocular,

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.

Bibliography

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

binocular

[bī′näk·yə·lər]
(biology)
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.
(optics)
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 ?
Normal values are reported as 8cpm binocularly and llcpm monocularly in adults when flippers comprising -2.
This P training involved repetitive and systematic alternation of the flippers every 15 to 20 s monocularly and binocularly, without any spherical lens power changes (i.
Because acquired visual dysfunction can be unilateral, all tests were administered separately for each eye, except for the Farnsworth D-15 (Bowman 1982), which was administered binocularly.
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It is comprised of a single lens mounted binocularly with dual, teardrop-shaped lenses and a bridge over the nose, which improves vision.
Although his visual acuity was reduced at 6/24 (20/80) binocularly by means of preferential looking using Cardiff cards; that is, he saw at 6 meters (about 20 feet) what someone with typical vision would see at 24 meters (about 79 feet), his visual difficulties were greater than expected for his level of visual acuity.
While working on humans towards the quantification of eye movements as an index of brain activity, Aserinsky and Kleitman (1) stumbled upon a stage within the state of sleep during which the behavioural observation and electro-oculographic recordings showed rapid, jerky and binocularly symmetrical eye movements with low voltage fast waves in the electroencephalogram (EEG).
Visual acuity was assessed for each eye separately as well as binocularly.
Acuity was measured binocularly for both high- and low-contrast scales with subjects wearing their best correction at a test distance of 4 m.
Although stereophotographic slides were used, participants in the study could choose at any time to view the slides monocularly (similar to an image obtained with a monocular direct opthalmoscope) or binocularly (similar to an image obtained with an indirect ophthalmoscope).
A patient may find it easier to keep the fellow eye open if it is fogged, rather than occluded, which also gives the opportunity to balance the vision binocularly at the same time.