Skip to main content
Select Source:

Binocular

Binocular

Background

Modern binoculars consist of two barrel chambers with an objective lens, eyepiece, and a pair of prisms inside. The prisms reflect and lengthen the light, while the objective lenses enhance and magnify images due to stereoscopic vision.

History

Man has been experimenting with glass since its advent sometime around 3500 b.c. These experiments soon became known for their ocular implications. The designs of early optical instruments, like the telescope, were not recorded. It is assumed that these instruments were studied and perfected by Galileo Galilei. Early binoculars were actually called binocular telescopes, and are thought to be based on Galileo's discoveries and designs of prisms.

Early telescopic lenses were full of bubbles and other imperfections. They were also slightly green due to the iron content in the glass. Polishing techniques were crude, and although lenses were of good quality in the center, the peripheral shape was poor resulting in a restricted aperture. As telescopes were improved, binoculars evolved. The first patent application for binocular telescopes was filed early in the seventeenth century by Jan Lippershey in present day Holland. Lippershey primarily used quartz crystal, which is hard to manipulate. The first hand-held binocular originated in 1702 with Johann Zahn's small binocular of two tubes with a lithe connection.

A patent application submitted in 1854 by Ignatio Porro began the use of the modern prism binocular called the Porro prism erecting system. This optical system consisted of an objective lens and ocular lens (eyepiece) with two facing, right angle prisms arranged to invert and correct the orientation of the image. The two most commonly used prism systems are the porro prism and the roof prism design. The roof system uses prisms positioned one over the other resulting in a more compact design.

An other major breakthrough occurred in 1894 when Carl Zeiss, a German optical specialist, developed binoculars with convex lenses and delta prisms to correct the inverted image. In a porro design, the light is bent in a "Z" shape before reaching the eye, allowing the distance between the eyepiece and the objective lens to be compacted. This enables the size and weight of binoculars to be reduced.

Reductions in the weight of the binoculars occurred with the use of aluminum or polycarbonate housings instead of the heavier metal alloys used in pre-civil war binoculars. Performance of smaller and larger binoculars has improved with the introduction of coatings to render the lenses non-reflective and reduce the amount of scattered light. The quality of prisms has also improved over the years, resulting in a reduction of the bubbling effect of optical glass. In the early 1970s, nitrogen filled, waterproof binoculars were developed. A decade later the arrival of infrared transmitters capable of seeing in the dark further transformed binocular technology. Variable magnification models were also developed allowing the user to adjust the level of magnification.

Raw Materials

Early binocular models had brass housing covers and were relatively heavy and expensive to produce. Subsequent leather or hard rubber covers were replaced in Germany during the World War I by a cover of black lacquered cardboard. Galvanized steel replaced the heavier brass in the housing covers. In the 1930s, nearly all of the metal parts of the service glasses were made of aluminum to save brass and reduce the weight.

Modern-day binocular tubes are primarily made out of aluminum coated with silicon or a leather-like material called gutta-percha. The lenses and prisms are made from glass and coated with an anti-reflective coating.

Design

With the exception of the optical glass and some rubber seals, the majority of binocular component parts can be manufactured using a Computer Assisted Design and Manufacturing (CAD/CAM) system that downloads the designs to a variety of Computer Numerically Controlled (CNC) devices (multi-axis mill turn and milling machines as well as vertical and horizontal machining centers, lathes, etc.). Using CAD software provides both drawing, dimensioning, and visualization capabilities. These lead to improvements in the binoculars final design.

The Manufacturing
Process

  1. The lens material is poured into a lens mold, which has a spherical curved bottom. This results in a lens that is about 4 in (10.2 cm) in diameter and 1-1.5 in (2.4-3.8 cm) thick.
  2. The lenses are then removed from the molds and cut into specific pieces using a diamond saw to create the optical lenses.
  3. The lenses are placed into the grinding machine and polished.
  4. After they have been carefully machined, the lenses are anodized to reduce reflections in vacuum tanks. The more coatings applied, the less light absorbed.
  5. The ocular lenses (nearest the eyes) are also molded and carefully polished by auto-polish machines after which they are centered on diamond turning machines and finally cleaned by running through several different solvents in automated machinery.
  6. The objective lenses, those furthest from the eyes, are molded and then polished with polishing machines.
  7. These components are then manually assembled into a die cast body, which is often made from aluminum.
  8. Using a technique called physical vapor deposition, the optics are placed into a "plasma machine" and coated with dielectric coatings. The coatings are essential for high performance.
  9. The optics are then inspected and tested for clarity and defects using lasers in specially designed particulate free rooms.
  10. Next, the rod shaped prisms are cut by lasers into three-sided shapes depending on the type of prism being manufactured (i.e., roof prisms or porro prisms).
  11. The prisms are coated with dielectric materials (metal oxides) by physical vapor deposition inside a vacuum chamber.
  12. When all these components are assembled on a belt assembly line, the final assembly station collimates the binocular by hand, making the left side exactly parallel to the right, so only one image will be seen at a time.
  13. The binocular housing is then covered with a substance called gutta-percha, which looks like leather but is more durable and flexible. This covering is applied by hand using an adhesive and may be coated with a protective rubber covering.
  14. On the assembly line bare metal housing covers are covered with plastic or rubber.
  15. The prisms are placed by hand inside the binocular casing and manually screwed in place.
  16. The objective lenses are held in place by a metal or plastic ring and the eyepiece is fitted with a rubber eyecap.
  17. The focusing lenses are placed in the housing with screws mounted by hand.
  18. Waterproof binoculars must have orings at every orifice, be purged with nitrogen (injected through a seal), and sealed. The final step would be the packing of binoculars in cases with neck straps, most cases today being of a canvas-like material.

Quality Control

Binoculars that have been hermetically sealed (waterproof) and nitrogen charged (fogproof) are tested underwater. Most binoculars will withstand water immersion at 16.4(5 m) for five minutes. Both barrels of a binocular need to be optically parallel for the image to merge into one perfect circle and are carefully checked for alignment.

Byproducts/Waste

Lenses and prisms that have defects such as scratches or cracks are either discarded and melted down to be molded again, or they are recycled. If the casing is damaged during production, it is also either remolded or recycled.

The Future

Binoculars continue to advance with new technology. Their ability to see further with better focusing techniques enables the consumer to use the product for a wider variety of tasks. Binoculars are now tending to use the same stabilizing method used in video cameras that automatically stabilizes the prism system so that the image remains steady to the viewer. Some binoculars are also coming equipped with night scope vision. This would enable the consumer to see objects that are far away even at night. Technological advancements are continually made on these specialty binoculars, which are primarily used by the military or for surveillance.

Where to Learn More

Books

Bell, Louis. The Telescope. McGraw-Hill Book Company, Inc., 1922.

Von Rohr, Moritz. Die Binokularen Instrumente. Berlin: Springer, 1920.

Other

The United States Patent Office Web Page. November 2001. <http://www.uspto.gov/patft>.

Van Helden, Albert. The Telescope. 1995. November 2001. <http://es.rice.edu/ES/humsoc/GalileoiThings/telescope.html>.

BonnyMcClain

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Binocular." How Products Are Made. . Encyclopedia.com. 14 Nov. 2018 <https://www.encyclopedia.com>.

"Binocular." How Products Are Made. . Encyclopedia.com. (November 14, 2018). https://www.encyclopedia.com/manufacturing/news-wires-white-papers-and-books/binocular

"Binocular." How Products Are Made. . Retrieved November 14, 2018 from Encyclopedia.com: https://www.encyclopedia.com/manufacturing/news-wires-white-papers-and-books/binocular

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

binocular

binocular, small optical instrument consisting of two similar telescopes 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).

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"binocular." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 14 Nov. 2018 <https://www.encyclopedia.com>.

"binocular." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (November 14, 2018). https://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/binocular

"binocular." The Columbia Encyclopedia, 6th ed.. . Retrieved November 14, 2018 from Encyclopedia.com: https://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/binocular

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

binoculars

binoculars Optical device, used with both eyes simultaneously, which produces a magnified image of a distant object or scene. It consists of a pair of identical telescopes, one for each eye, both containing an objective lens, an eyepiece lens, and an optical system (usually prisms), to form an upright image. Binoculars are classified by two numbers, such as 8×30, with the first number indicating the magnification and the second being the diameter of the objective lens (nearest to the object) in millimetres. Field glasses are a common type of binoculars.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"binoculars." World Encyclopedia. . Encyclopedia.com. 14 Nov. 2018 <https://www.encyclopedia.com>.

"binoculars." World Encyclopedia. . Encyclopedia.com. (November 14, 2018). https://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/binoculars

"binoculars." World Encyclopedia. . Retrieved November 14, 2018 from Encyclopedia.com: https://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/binoculars

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

binocular

binocular (bin-ok-yoo-ler) adj. relating to or involving the use of both eyes. b. vision the acquired ability to focus both eyes on an object at the same time, so that only one image is seen.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"binocular." A Dictionary of Nursing. . Encyclopedia.com. 14 Nov. 2018 <https://www.encyclopedia.com>.

"binocular." A Dictionary of Nursing. . Encyclopedia.com. (November 14, 2018). https://www.encyclopedia.com/caregiving/dictionaries-thesauruses-pictures-and-press-releases/binocular

"binocular." A Dictionary of Nursing. . Retrieved November 14, 2018 from Encyclopedia.com: https://www.encyclopedia.com/caregiving/dictionaries-thesauruses-pictures-and-press-releases/binocular

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

binocular

bin·oc·u·lar / biˈnäkyələr/ • adj. adapted for or using both eyes: a binocular microscope.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"binocular." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 14 Nov. 2018 <https://www.encyclopedia.com>.

"binocular." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (November 14, 2018). https://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/binocular-0

"binocular." The Oxford Pocket Dictionary of Current English. . Retrieved November 14, 2018 from Encyclopedia.com: https://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/binocular-0

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

binocular

binocular adapted to both eyes XVIII; sb. pl. field or opera glasses XIX. f. L. bīnī two together (cf. BI-) + oculus EYE, after OCULAR.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"binocular." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. 14 Nov. 2018 <https://www.encyclopedia.com>.

"binocular." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. (November 14, 2018). https://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/binocular-1

"binocular." The Concise Oxford Dictionary of English Etymology. . Retrieved November 14, 2018 from Encyclopedia.com: https://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/binocular-1

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

binocular

binocularampulla, bulla, fuller, Müller, pula, puller •titular • Weissmuller • wirepuller •incunabula, tabular •preambular • glandular • coagula •angular, quadrangular, rectangular, triangular •Dracula, facula, oracular, spectacular, vernacular •cardiovascular, vascular •annular, granular •scapula • capsular • spatula •tarantula • nebula • scheduler •calendula •irregular, regular •Benbecula, molecular, secular, specular •cellular • fibula • Caligula • singular •auricular, curricula, curricular, diverticula, funicular, lenticular, navicular, particular, perpendicular, testicular, vehicular, vermicular •primula •insular, peninsula •fistula, Vistula •globular •modular, nodular •binocular, jocular, ocular •oscular •copula, popular •consular • formula • tubular • uvula •jugular •avuncular, carbuncular •crepuscular, majuscular, minuscular, muscular •pustular •circular, semicircular, tubercular •Ursula

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"binocular." Oxford Dictionary of Rhymes. . Encyclopedia.com. 14 Nov. 2018 <https://www.encyclopedia.com>.

"binocular." Oxford Dictionary of Rhymes. . Encyclopedia.com. (November 14, 2018). https://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/binocular

"binocular." Oxford Dictionary of Rhymes. . Retrieved November 14, 2018 from Encyclopedia.com: https://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/binocular

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

Binocular

Binocular

Binoculars, sometimes called binocular telescopes, are hand-held optical instruments that are used to magnify distant objects. However, before the early 1800s they did not exist. In 1823, a new optical instrument began to appear in French opera houses that allowed patrons in the distant (and less expensive) seats to view the opera as if they were in the front row. Called opera glasses, the device combined telescope lenses with stereoscopic prisms to provide a magnified, three-dimensional view. After many years (but relatively few modifications), opera glasses have evolved into binoculars.

In their simplest form, binoculars are a pair of small refracting telescope lenses, one for each eye. The brain assembles the two views, one from each lens, into a single picture. Because each eye sees its own view, the final image has depth; this is not so with conventional telescopes, which possess only one eyepiece and, therefore, a two-dimensional image.

While some simple binoculars can be found, most quality binoculars possess a more intricate design. In complex binoculars, there is a system of prisms between the large front lens, called the objective lens, and the smaller eyepiece. These prisms serve two important functions. First, they bend the light so that the final image is both upright and non-reversed. In a common telescopic view, the image is both reversed and upside-down. Second, the bending produced by the prisms lengthens the overall light path, which allows for much greater magnification while staying within the binoculars short tube. Without prisms, average-powered binoculars would need to be more than one foot (0.305 m) in length.

In order to enhance the stereoscopic, or three-dimensional, effect, the binoculars two objective lenses are placed further apart than the viewers eyes. When the two views are then assembled by the brain, a greater impression of depth and clarity results.

Many different factors influence the quality of a binocular. For the majority of users, the most important of these is magnifying power. Binocular magnification usually ranges from six to twenty timesthat is, the object appears six to twenty times larger in the binoculars than it would with the unaided eye. Magnification is usually expressed as X, whereby six times magnification would be written 6 X.

Another factor governing a binoculars quality is the size of the two object lenses, called the aperture. Larger aperture sizes are valued, because they collect a greater amount of light. This is crucial, because an image becomes fainter as the magnification increases. Thus, high magnifications are usually coupled with wide apertures. While object lenses of 30 to 80 mm (1 to 3 in) are common, apertures as large as 150 mm (6 in) have been designed. These binoculars, however, are used chiefly in military reconnaissance. Binocular makers generally express the quality of their instruments in terms of both magnification and aperture size. A common rating is 7 × 50, which describes a magnification of seven power and an aperture of 50 mm (2 in).

Professional users of binoculars, such as astronomers and military personnel, also consider the size of the light beam that exits the eyepiece, called the exit pupil. The closer this light beam is to the width of the viewers own pupil, the more efficient the binocular. This is a tricky factor because the size of a human pupil varies: in bright light (such as daylight) the pupil is only 0.078 in (2 mm) across, while in dim light (such as moonlight) it opens to almost 0.273 in (7 mm). Thus, binoculars with a small exit pupil are best for daytime use, while those with a wider exit pupil are essential for nighttime observing.

Yet another factor affecting the quality of a binocular is the straightness of its beams. In a perfectly adjusted instrument, the two beams entering each eye will be parallel. If these beams are offset even slightly, a doubled image will be produced. Such a poorly adjusted view is uncomfortable and bad for the eyes. In order to fix the image, the binoculars should be collimated so that the beams are parallel.

Although they are inferior to telescopes in magnification, binoculars are often better devices for viewing the night sky. Because of their wider object lenses, binoculars can collect more light than telescopes; this makes objects such as distant stars or planetary satellites appear much brighter than they would in many telescopes. Even household binoculars are sufficient for viewing the moon and the visible planets, and they are usually much less expensive than a telescope.

Obviously unable to be held by human hands (which is part of the definition of binoculars), the Large Binocular Telescope Observatory (LBTO) located in Arizona is a gigantic version of the binocular. As a joint effort of Germany, Italy, and United States, the LBTOonce fully operationalwill use two 8.4-meter reflector telescopes mounted on a common base (thus the name binocular) for studies in the optical range of the electromagnetic spectrum. As of May 2006, the binocular telescope is under construction, with only one of the telescopes being operational. However, sometime at the end of 2006 or in early 2007, the second telescope is expected to become operational.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Binocular." The Gale Encyclopedia of Science. . Encyclopedia.com. 14 Nov. 2018 <https://www.encyclopedia.com>.

"Binocular." The Gale Encyclopedia of Science. . Encyclopedia.com. (November 14, 2018). https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/binocular

"Binocular." The Gale Encyclopedia of Science. . Retrieved November 14, 2018 from Encyclopedia.com: https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/binocular

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

Binocular

Binocular

In 1823, a new optical instrument began to appear in French opera houses that allowed patrons in the distant (and less expensive) seats to view the opera as if they were in the front row. Called opera glasses, the device combined telescope lenses with stereoscopic prisms to provide a magnified, three-dimensional view. After many years (but relatively few modifications), opera glasses have evolved into the binocular.

In their simplest form, binoculars are a pair of small refracting telescope lenses, one for each eye . The brain assembles the two views, one from each lens , into a single picture. Because each eye sees its own view, the final image has depth; this is not so with conventional telescopes, which possess only one eyepiece and, therefore, a two-dimensional image.

While some simple binoculars can be found, most quality binoculars possess a more intricate design. In more complex binoculars, there is a system of prisms between the large front lens, called the objective lens, and the smaller eyepiece. These prisms serve two important functions. First, they bend the light so that the final image is both upright and nonreversed. In a common telescopic view, the image is both reversed and upside-down. Second, the bending produced by the prisms lengthens the overall light path, which allows for much greater magnification while staying within the binocular's short tube. Without prisms, average-powered binoculars would need to be more than one foot (0.305 m) in length.

In order to enhance the stereoscopic, or three-dimensional, effect, the binocular's two objective lenses are placed further apart than the viewer's eyes. When the two views are then assembled by the brain, a greater impression of depth and clarity results.

Many different factors influence the quality of a binocular. For the majority of users, the most important of these is magnifying power. Binocular magnification usually ranges from six to twenty times—that is, the object appears six to twenty times larger in the binoculars than it would with the unaided eye. Magnification is usually expressed as "X," whereby six times magnification would be written 6 X.

Another factor governing a binocular's quality is the size of the two object lenses, called the aperture. Larger aperture sizes are valued, because they collect a greater amount of light. This is crucial, because an image becomes fainter as the magnification increases. Thus, high magnifications are usually coupled with wide apertures. While object lenses of 30-80 mm (1-3 in) are common, apertures as large as 150 mm (6 in) have been designed; these, however, are used chiefly in military reconnaissance. Binocular makers generally express the quality of their instruments in terms of both magnification and aperture size. A common rating is 7 × 50, which describes a magnification of seven power and an aperture of 50 mm (2 in).

Professional users of binoculars, such as astronomers and military personnel, also consider the size of the light beam that exits the eyepiece, called the exit pupil. The closer this light beam is to the width of the viewer's own pupil, the more efficient the binocular. This is a tricky factor because the size of a human pupil varies: in bright light (such as daylight) the pupil is only 0.078 in (2 mm) across, while in dim light (such as moonlight) it opens to almost 0.273 in (7 mm). Thus, binoculars with a small exit pupil are best for daytime use, while those with a wider exit pupil are essential for nighttime observing.

Yet another factor affecting the quality of a binocular is the straightness of its beams. In a perfectly adjusted instrument, the two beams entering each eye will be parallel . If these beams are offset even slightly, a doubled image will be produced. Such a poorly adjusted view is uncomfortable and bad for the eyes. In order to fix the image, the binoculars should be collimated so that the beams are parallel.

Although they are inferior to telescopes in magnification, binoculars are often better devices for viewing the heavens. Because of their wider object lenses, binoculars can collect more light than telescopes; this makes objects such as distant stars or planetary satellites appear much brighter than they would in many telescopes. Even household binoculars are sufficient for viewing the Moon and the visible planets, and they are usually much less expensive than a telescope.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Binocular." The Gale Encyclopedia of Science. . Encyclopedia.com. 14 Nov. 2018 <https://www.encyclopedia.com>.

"Binocular." The Gale Encyclopedia of Science. . Encyclopedia.com. (November 14, 2018). https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/binocular-0

"Binocular." The Gale Encyclopedia of Science. . Retrieved November 14, 2018 from Encyclopedia.com: https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/binocular-0

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.