A lens.

A lens (or lense) is an optical device with perfect or approximate axial symmetry which transmits and refracts light, concentrating or diverging the beam. A simple lens is a lens consisting of a single optical element. A compound lens is an array of simple lenses (elements) with a common axis; the use of multiple elements allows more optical aberrations to be corrected than is possible with a single element. Manufactured lenses are typically made of glass or transparent plastic. Elements which refract electromagnetic radiation outside the visual spectrum are also called lenses: for instance, a microwave lens can be made from paraffin wax. Look up lens in Wiktionary, the free dictionary. ... Image File history File links Download high resolution version (809x602, 34 KB) Summary eo Ebenkonveksa lenso. ... Image File history File links Download high resolution version (809x602, 34 KB) Summary eo Ebenkonveksa lenso. ... For the book by Sir Isaac Newton, see Opticks. ... In quantum field theory, chiral symmetry is a possible symmetry of the Lagrangian under which the left-handed and right-handed parts of Dirac fields transform independently. ... In the fields of optics and spectroscopy, transmittance is the fraction of incident light at a specified wavelength that passes through a sample. ... The straw seems to be broken, due to refraction of light as it emerges into the air. ... This article does not cite any references or sources. ... A simple lens is a lens consisting of a single simple element. ... Aberration in optical systems (lenses, prisms, mirrors or series of them intended to produce a sharp image) generally leads to blurring of the image. ... This article is about the material. ... See: transparency (optics) alpha compositing GIF#Transparency transparency (overhead projector) market transparency transparency (telecommunication) transparency (computing) For X11 pseudo-transparency, see pseudo-transparency. ... This article or section does not cite any references or sources. ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... This article is about the type of Electromagnetic radiation. ... Paraffin is a common name for a group of high molecular weight alkane hydrocarbons with the general formula CnH2n+2, where n is greater than about 20. ...

History

See also: History of optics

The oldest lens artefact is dated to c.640 BC, a rock crystal lens found at excavations in Niniveh. The earliest written records of lenses date to Ancient Greece, with Aristophanes' play The Clouds (424 BC) mentioning a burning-glass (a biconvex lens used to focus the sun's rays to produce fire). The writings of Pliny the Elder (23–79) also show that burning-glasses were known to the Roman Empire^[1], and mentions what is possibly the first use of a corrective lens: Nero was said to watch the gladiatorial games using an emerald^[2] (presumably concave to correct for myopia, though the reference is vague). Both Pliny and Seneca the Younger (3 BC–65) described the magnifying effect of a glass globe filled with water. // The Beginnings of Geometrical Optics The Greek term τα όπτικά referred specifically to matters of vision[1], and hence early optics was concerned with the problem of how we see. ... Centuries: 8th century BC - 7th century BC - 6th century BC Decades: 690s BC 680s BC 670s BC 660s BC 650s BC - 640s BC - 630s BC 620s BC 610s BC 600s BC 590s BC Events and Trends Assyrian king Ashurbanipal founds library, which includes our earliest complete copy of the Epic... For other uses, see Quartz (disambiguation). ... This article is about the ancient Middle Eastern city of Nineveh. ... Ancient Greece is the term used to describe the Greek-speaking world in ancient times. ... Sketch of Aristophanes Aristophanes (Greek: , ca. ... The Clouds (Νεφέλαι) is a comedy written by the Ancient Greek playwright Aristophanes lampooning the sophists and the intellectual trends of late fifth-century Athens. ... Centuries: 6th century BC - 5th century BC - 4th century BC Decades: 470s BC 460s BC 450s BC 440s BC 430s BC - 420s BC - 410s BC 400s BC 390s BC 380s BC 370s BC Years: 429 BC 428 BC 427 BC 426 BC 425 BC - 424 BC - 423 BC 422 BC... A burning-glass is a large convex lens that can concentrate the suns rays onto a small area, heating up the area and thus resulting in ignition of the surface exposed. ... An image that is partially in focus, but mostly out of focus in varying degrees. ... Sol redirects here. ... Pliny the Elder: an imaginative 19th Century portrait. ... Year 23 was a common year starting on Friday (link will display the full calendar) of the Julian calendar. ... This article is about the year 79. ... For other uses, see Roman Empire (disambiguation). ... A bifocal corrective eyeglasses lens A corrective lens is a lens worn on or before the eye, used to treat myopia, hyperopia, astigmatism, and presbyopia. ... For other uses, see Nero (disambiguation). ... For other uses, see Gladiator (disambiguation). ... This article or section does not cite its references or sources. ... Normal vision. ... Bust, traditionally thought to be Seneca, now identified by some as Hesiod. ... Events Births Seneca, Roman statesman Servius Sulpicius Galba, Roman emperor Jesus Christ born September 11 Deaths Imperial consort Fu Category: ... Headline text Events By place Roman Empire Gaius Calpurnius Piso conspires against Roman emperor Nero. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ...

The Arabian mathematician Ibn Sahl (c.940–c.1000) used what is now known as Snell's law to calculate the shape of lenses.^[3] Ibn al-Haitham (965–1038) wrote the first major optical treatise, the Book of Optics, which described how the lens in the human eye formed an image on the retina. Islamic mathematics is the profession of Muslim Mathematicians. ... Ibn Sahl - Wikipedia, the free encyclopedia /**/ @import /skins-1. ... Events Births Brian Boru, high king of Ireland Abul-Wafa, iranian mathematician Deaths ar-Radi (Caliph of Baghdad) Athelstan, who was succeeded by his half-brother, Edmund Categories: 940 ... Europe in 1000 The year 1000 of the Gregorian Calendar was the last year of the 10th century as well as the last year of the first millennium. ... Refraction of light at the interface between two media of different refractive indices, with n2 > n1. ... Ibn al-Haytham depicted in an Iraqi 10,000-dinar note. ... March 1 - Pope Leo VIII is restored in place of Pope Benedict V October 1 - Pope John XIII succeeds Pope Leo VIII as the 133rd pope. ... Events Independent declaration of Western Xia. ... For the book by Sir Isaac Newton, see Opticks. ... The title page of a 1572 Latin manuscript of Ibn al-Haythams Book of Optics The Book of Optics (Arabic: Kitab al-Manazir, Latin: De Aspectibus or Perspectiva) was a seven volume treatise on optics written by the Iraqi Muslim scientist Ibn al-Haytham (Latinized as Alhacen or Alhazen... Light from a single point of a distant object and light from a single point of a near object being brought to a focus by changing the curvature of the lens. ... For other uses, see Eye (disambiguation). ... Human eye cross-sectional view. ...

Excavations at the Viking harbour town of Fröjel, Gotland, Sweden discovered in 1999 the rock crystal Visby lenses, produced by turning on pole-lathes at Fröjel in the 11th to 12th century, with an imaging quality comparable to that of 1950s aspheric lenses. The Viking lenses concentrate sunlight enough to ignite fires. For other uses, see Viking (disambiguation). ...   is a county, province and municipality of Sweden and the second largest island in the Baltic Sea after Zealand. ... The Visby lenses are ten lens-shaped rock crystals found in a viking grave in Gotland dating from the 10th century. ...

Widespread use of lenses did not occur until the use of reading stones in the 11th century and the invention of spectacles, probably in Italy in the 1280s. Nicholas of Cusa is believed to have been the first to discover the benefits of concave lenses for the treatment of myopia in 1451. A reading stone was an approximately hemispherical transparent object placed on top of text to magnify the letters so that people with presbyopia could read the text more easily. ... Glasses, spectacles, or eyeglasses are frames bearing lenses worn in front of the eyes, sometimes for purely aesthetic reasons but normally for vision correction or eye protection. ... The 1280s is the decade starting January 1, 1280 and ending December 31, 1289. ... Nicholas of Cusa Nicholas of Cusa (1401– August 11, 1464) was a German cardinal of the Roman Catholic Church, a philosopher, jurist, mathematician, and an astronomer. ... Normal vision. ... // Events February 3 - Murad II, Sultan of the Ottoman Empire dies and is succeeded by his son Mehmed II. April 11 - Celje acquires market-town status and town rights by orders from the Celje count Frederic II. June 30 - French troops under the Comte de Dunois invade Guyenne and capture...

The Abbe sine condition, due to Ernst Abbe (1860s), is a condition that must be fulfilled by a lens or other optical system in order for it to produce sharp images of off-axis as well as on-axis objects. It revolutionized the design of optical instruments such as microscopes, and helped to establish the Carl Zeiss company as a leading supplier of optical instruments. Abbe sin condition was the masterwork of Ernest Abbe. ... Ernst Karl Abbe Ernst Karl Abbe (January 23, 1840 in Eisenach – January 14, 1905 in Jena), was a German physicist. ... A microscope (Greek: micron = small and scopos = aim) is an instrument for viewing objects that are too small to be seen by the naked or unaided eye. ... Carl Zeiss (September 11, 1816 – December 3, 1888) was an optician commonly known for the company he founded, Zeiss. ...

Construction of simple lenses

Image of the city of Seattle as seen through a lens.

Most lenses are spherical lenses: their two surfaces are parts, with the same axis as each other, of the surfaces of spheres. Each surface can be convex (bulging outwards from the lens), concave (depressed into the lens), or planar (flat). The line joining the centres of the spheres making up the lens surfaces is called the axis of the lens; in almost all cases the lens axis passes through the physical centre of the lens. Image File history File linksMetadata Download high-resolution version (3504x2336, 2658 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Lens (optics) Metadata This file contains additional information, probably added from the digital camera or scanner used to... Image File history File linksMetadata Download high-resolution version (3504x2336, 2658 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Lens (optics) Metadata This file contains additional information, probably added from the digital camera or scanner used to... City nickname Emerald City City bird Great Blue Heron City flower Dahlia City mottos The City of Flowers The City of Goodwill City song Seattle, the Peerless City Mayor Greg Nickels County King County Area   - Total   - Land   - Water   - % water 369. ...

Types of simple lenses

Lenses are classified by the curvature of the two optical surfaces. A lens is biconvex (or double convex, or just convex) if both surfaces are convex, A lens with two concave surfaces is biconcave (or just concave). If one of the surfaces is flat, the lens is plano-convex or plano-concave depending on the curvature of the other surface. A lens with one convex and one concave side is convex-concave or meniscus.

If the lens is biconvex or plano-convex, a collimated or parallel beam of light travelling parallel to the lens axis and passing through the lens will be converged (or focused) to a spot on the axis, at a certain distance behind the lens (known as the focal length). In this case, the lens is called a positive or converging lens. Image File history File links This is a lossless scalable vector image. ... Collimated light is light whose rays are parallel. ... This article is about focal length related to lenses and systems of lenses. ...

Image File history File links Lens1. ... Convex lens Taken by fir0002 File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...

If the lens is biconcave or plano-concave, a collimated beam of light passing through the lens is diverged (spread); the lens is thus called a negative or diverging lens. The beam after passing through the lens appears to be emanating from a particular point on the axis in front of the lens; the distance from this point to the lens is also known as the focal length, although it is negative with respect to the focal length of a converging lens.

Image File history File links Lens1b. ... Concave lens Taken by fir0002 File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...

If the lens is convex-concave (a meniscus lens), whether it is converging or diverging depends on the relative curvatures of the two surfaces. If the curvatures are equal, then the beam is neither converged nor diverged.

Lensmaker's equation

The focal length of a lens in air can be calculated from the lensmaker's equation:^[4]

where

f is the focal length of the lens,

n is the refractive index of the lens material,

R₁ is the radius of curvature of the lens surface closest to the light source,

R₂ is the radius of curvature of the lens surface farthest from the light source, and

d is the thickness of the lens (the distance along the lens axis between the two surface vertices).

The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. ... The cardinal points and the associated cardinal planes are a set of special points and planes in an optical system, which help in the analysis of its paraxial properties. ...

Sign convention of lens radii R₁ and R₂

Main article: Radius of curvature (optics)

The signs of the lens' radii of curvature indicate whether the corresponding surfaces are convex or concave. The sign convention used to represent this varies, but in this article if R₁ is positive the first surface is convex, and if R₁ is negative the surface is concave. The signs are reversed for the back surface of the lens: if R₂ is positive the surface is concave, and if R₂ is negative the surface is convex. If either radius is infinite, the corresponding surface is flat. The term radius of curvature has specific meaning and sign convention in optical design. ... In physics, a sign convention is a choice of the signs (plus or minus) of a set of quantities, in a case where the choice of sign is arbitrary. ... The infinity symbol ∞ in several typefaces. ...

Thin lens equation

If d is small compared to R₁ and R₂, then the thin lens approximation can be made. For a lens in air, f is then given by A lens can be considered a thin lens if d << f. ...

^[5]

The focal length f is positive for converging lenses, negative for diverging lenses, and infinite for meniscus lenses. The value 1/f is known as the optical power of the lens, and so meniscus lenses are said to have zero power. Lens power is measured in dioptres, which are units equal to inverse meters (m⁻¹). Optical power or dioptric power or refractive power is the degree to which a lens or mirror converges or diverges light. ... A dioptre, or diopter, is a non-SI unit of measurement of the optical power of a lens or curved mirror, which is equal to the reciprocal of the focal length measured in metres (i. ...

Lenses have the same focal length when light travels from the back to the front as when light goes from the front to the back, although other properties of the lens, such as the aberrations are not necessarily the same in both directions. This article or section is in need of attention from an expert on the subject. ...

Imaging properties

As mentioned above, a positive or converging lens in air will focus a collimated beam travelling along the lens axis to a spot (known as the focal point) at a distance f from the lens. Conversely, a point source of light placed at the focal point will be converted into a collimated beam by the lens. These two cases are examples of image formation in lenses. In the former case, an object at an infinite distance (as represented by a collimated beam of waves) is focused to an image at the focal point of the lens. In the latter, an object at the focal length distance from the lens is imaged at infinity. The plane perpendicular to the lens axis situated at a distance f from the lens is called the focal plane. An image that is partially in focus, but mostly out of focus in varying degrees. ... Look up point source in Wiktionary, the free dictionary. ... It has been suggested that this article or section be merged into image (disambiguation). ...

Image File history File links Lens3. ...

If the distances from the object to the lens and from the lens to the image are S₁ and S₂ respectively, for a lens of negligible thickness, in air, the distances are related by the thin lens formula:

.

What this means is that, if an object is placed at a distance S₁ along the axis in front of a positive lens of focal length f, a screen placed at a distance S₂ behind the lens will have an image of the object projected onto it, as long as S₁ > f. This is the principle behind photography. The image in this case is known as a real image. Photography [fÓ™tÉ‘grÓ™fi:],[foÊŠtÉ‘grÓ™fi:] is the process of recording pictures by means of capturing light on a light-sensitive medium, such as a film or electronic sensor. ... Top: The formation of a real image using a convex lens. ...

Image File history File links Lens3b. ...

Note that if S₁ < f, S₂ becomes negative, the image is apparently positioned on the same side of the lens as the object. Although this kind of image, known as a virtual image, cannot be projected on a screen, an observer looking through the lens will see the image in its apparent calculated position. A magnifying glass creates this kind of image. Top: The formation of a virtual image using a concave lens. ... A magnifying glass is a single convex lens which is used to see girls better it is wonderful i love eating it is so tasty a mg is used also toproduce a magnified image of an object. ...

The magnification of the lens is given by: Magnification is the process of enlarging something only in appearance, not physical size. ...

,

where M is the magnification factor; if |M|>1, the image is larger than the object. Notice the sign convention here shows that, if M is negative, as it is for real images, the image is upside-down with respect to the object. For virtual images, M is positive and the image is upright.

In the special case that S₁ = ∞, then S₂ = f and M = −f / ∞ = 0. This corresponds to a collimated beam being focused to a single spot at the focal point. The size of the image in this case is not actually zero, since diffraction effects place a lower limit on the size of the image (see Rayleigh criterion). The intensity pattern formed on a screen by diffraction from a square aperture Diffraction refers to various phenomena associated with wave propagation, such as the bending, spreading and interference of waves passing by an object or aperture that disrupts the wave. ... Resolving power is the ability of a microscope or telescope to measure the angular separation of images that are close together. ...

Image File history File links Lens4. ...

The formulas above may also be used for negative (diverging) lens by using a negative focal length (f), but for these lenses only virtual images can be formed.

For the case of lenses that are not thin, or for more complicated multi-lens optical systems, the same formulas can be used, but S₁ and S₂ are interpreted differently. If the system is in air or vacuum, S₁ and S₂ are measured from the front and rear principal planes of the system, respectively. Imaging in media with an index of refraction greater than 1 is more complicated, and is beyond the scope of this article. Look up Vacuum in Wiktionary, the free dictionary. ... The cardinal points and the associated cardinal planes are a set of special points and planes in an optical system, which help in the analysis of its paraxial properties. ...

Aberrations

Main article: Aberration in optical systems

Lenses do not form perfect images, and there is always some degree of distortion or aberration introduced by the lens which causes the image to be an imperfect replica of the object. Careful design of the lens system for a particular application ensures that the aberration is minimized. There are several different types of aberration which can affect image quality. This article or section is in need of attention from an expert on the subject. ...

Spherical aberration

Spherical aberration occurs because spherical surfaces are not the ideal shape with which to make a lens, but they are by far the simplest shape to which glass can be ground and polished and so are often used. Spherical aberration causes beams parallel to but away from the lens axis to be focused in a slightly different place than beams close to the axis. This manifests itself as a blurring of the image. Lenses in which closer-to-ideal, non-spherical surfaces are used are called aspheric lenses. These were formerly complex to make and often extremely expensive, although advances in technology have greatly reduced the cost of manufacture for these lenses. Spherical aberration can be minimised by careful choice of the curvature of the surfaces for a particular application: for instance, a plano-convex lens which is used to focus a collimated beam produces a sharper focal spot when used with the convex side towards the beam. Focal plane Longitudinal sections In optics, spherical aberration is an image imperfection that occurs due to the increased refraction of light rays that occurs when rays strike a lens or mirror near its edge, in comparison with those that strike nearer the center. ... An aspheric lens or asphere is a lens whose surfaces have a profile that is neither a portion of a sphere nor of a circular cylinder. ...

Image File history File links Lens5. ...

Coma

Another type of aberration is coma, which derives its name from the comet-like appearance of the aberrated image. Coma occurs when an object off the optical axis of the lens is imaged, where rays pass through the lens at an angle to the axis θ. Rays which pass through the centre of the lens of focal length f are focused at a point with distance f tan θ from the axis. Rays passing through the outer margins of the lens are focused at different points, either further from the axis (positive coma) or closer to the axis (negative coma). In general, a bundle of parallel rays passing through the lens at a fixed distance from the centre of the lens are focused to a ring-shaped image in the focal plane, known as a comatic circle. The sum of all these circles results in a V-shaped or comet-like flare. As with spherical aberration, coma can be minimised (and in some cases eliminated) by choosing the curvature of the two lens surfaces to match the application. Lenses in which both spherical aberration and coma are minimised are called bestform lenses. In optics (especially telescopes), the coma in an optical system refers to monochromatic aberration inherent to certain optical designs or due to imperfection in the lens or other components which results in off-axis point sources such as stars appearing distorted. ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ...

Image File history File links Lens-coma. ...

Chromatic aberration

Chromatic aberration is caused by the dispersion of the lens material, the variation of its refractive index n with the wavelength of light. Since from the formulae above f is dependent on n, it follows that different wavelengths of light will be focused to different positions. Chromatic aberration of a lens is seen as fringes of colour around the image. It can be minimised by using an achromatic doublet (or achromat) in which two materials with differing dispersion are bonded together to form a single lens. This reduces the amount of chromatic aberration over a certain range of wavelengths, though it does not produce perfect correction. The use of achromats was an important step in the development of the optical microscope. An apochromat is a lens or lens system which has even better correction of chromatic aberration, combined with improved correction of spherical aberration. Apochromats are much more expensive than achromats. Chromatic aberration is caused by the dispersion of the lens material, the variation of its refractive index n with the wavelength of light. ... Dispersion of a light beam in a prism. ... The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. ... Diagram of an achromatic lens (doublet). ... Apochromatic is a description of a photographic or other lens having a high degree of color correction. ...

Image File history File links Lens6a. ... Image File history File links Lens6b. ...

Other kinds of aberration include field curvature, barrel and pincushion distortion, and astigmatism. Aberration in optical systems (lenses, prisms, mirrors or series of them intended to produce a sharp image) generally leads to blurring of the image. ... Barrel Simulation Barrel distortion is a divergence from the rectilinear projection in geometric optics where image magnification decreases with increasing distance from the optical axis. ... Pincushion Simulation Pincushion distortion is a divergence from the rectilinear projection in geometric optics where image magnification increases with increasing distance from the optical axis. ... In optics, astigmatism is when an optical system has different foci for rays that propagate in two perpendicular planes. ...

Aperture diffraction

Even if a lens is designed to minimize or eliminate the aberrations described above, the image quality is still limited by the diffraction of light passing through the lens' finite aperture. A diffraction-limited lens is one in which aberrations have been reduced to the point where the image quality is primarily limited by diffraction under the design conditions. The intensity pattern formed on a screen by diffraction from a square aperture Diffraction refers to various phenomena associated with wave propagation, such as the bending, spreading and interference of waves passing by an object or aperture that disrupts the wave. ...

Compound lenses

See also: Photographic lens, Doublet (lens), and Achromat

Simple lenses are subject to the optical aberrations discussed above. In many cases these aberrations can be compensated for to a great extent by using a combination of simple lenses with complementary aberrations. A compound lens is a collection of simple lenses of different shapes and made of materials of different refractive indices, arranged one after the other with a common axis. Photographic lens One of Canons most popular wide angle lenses - 17-40 f/4 L The zoom lens of the Canon Elph A photographic lens (or more correctly, objective) is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images... For other uses, see Doublet. ... Chromatic aberration is caused by the dispersion of the lens material, the variation of its refractive index n with the wavelength of light. ...

The simplest case is where lenses are placed in contact: if the lenses of focal lengths f₁ and f₂ are "thin", the combined focal length f of the lenses is: A lens can be considered a thin lens if d << f. ...

.

Since 1/f is the power of a lens, it can be seen that the powers of thin lenses in contact are additive.

If two thin lenses are separated by some distance d, the distance from the second lens to the focal point of the combined lenses is called the back focal length (BFL). This is given by:

.

Note that as d tends to zero, the value of the BFL tends to the value of f given for thin lenses in contact.

If the separation distance is equal to the sum of the focal lengths (d = f₁+f₂), the BFL is infinite. This corresponds to a pair of lenses that transform a parallel (collimated) beam into another collimated beam. This type of system is called afocal, since it produces no net convergence or divergence of the beam. Two lenses at this separation form the simplest type of optical telescope. Eight Inch refracting telescope. ...

Although the system does not alter the divergence of a collimated beam, it does alter the width of the beam. The magnification of the telescope is given by:

,

which is the ratio of the input beam width to the output beam width. Note the sign convention: a telescope with two convex lenses (f₁ > 0, f₂ > 0) produces a negative magnification, indicating an inverted image. A convex plus a concave lens (f₁ > 0 > f₂) produces a positive magnification and the image is upright.

Uses of lenses

A single convex lens mounted in a frame with a handle or stand is a magnifying glass. A magnifying glass is a single convex lens which is used to see girls better it is wonderful i love eating it is so tasty a mg is used also toproduce a magnified image of an object. ...

Lenses are used as prosthetic for the correction of visual impairments such as myopia, hyperopia, presbyopia, and astigmatism. See corrective lens, contact lens, eyeglasses. Most lenses used for other purposes have strict axial symmetry; eyeglass lenses are only approximately symmetric. They are shaped to fit in a usually roughly oval, not circular, frame; the optical centers are placed over the eyeballs; their curvature may not be axially symmetric to correct for astigmatism. Sunglasses lenses may be designed to attenuate light without refraction. A United States soldier demonstrates Foosball with two prosthetic limbs In medicine, a prosthesis is an artificial extension that replaces a missing part of the body. ... Visual impairment is the functional loss of vision. ... Normal vision. ... Hyperopia, also known as hypermetropia or colloquially as farsightedness or longsightedness, is a defect of vision caused by an imperfection in the eye (often when the eyeball is too short or when the lens cannot become round enough), causing inability to focus on near objects, and in extreme cases causing... Presbyopia (Greek word presbyteros (πρεσβύτερος), meaning elder) is the eyes diminished ability to focus that occurs with aging. ... In optics, astigmatism is when an optical system has different foci for rays that propagate in two perpendicular planes. ... A bifocal corrective eyeglasses lens A corrective lens is a lens worn on or before the eye, used to treat myopia, hyperopia, astigmatism, and presbyopia. ... A pair of contact lenses, positioned with the concave side facing upward. ... Glasses, spectacles, or eyeglasses are frames bearing lenses worn in front of the eyes, sometimes for purely aesthetic reasons but normally for vision correction or eye protection. ... In quantum field theory, chiral symmetry is a possible symmetry of the Lagrangian under which the left-handed and right-handed parts of Dirac fields transform independently. ... Wikipedia does not yet have an article with this exact name. ... In optics, astigmatism is when an optical system has different foci for rays that propagate in two perpendicular planes. ... Ray-Ban Wayfarer sunglasses (RB2132 901L) Sunglasses are a visual aid, variously termed spectacles or glasses, which feature lenses that are coloured or darkened to prevent strong light from reaching the eyes. ...

Another use is in imaging systems such as a monocular, binoculars, telescope, spotting scope, telescopic gun sight, theodolite, microscope, camera (photographic lens) and projector. Some of these instruments produce a virtual image when applied to the human eye; others produce a real image which can be captured on photographic film or an optical sensor. A monocular is a modified refracting telescope used to magnify the images of distant objects by passing light through a series of lenses and prisms; the use of prisms results in a lightweight telescope. ... Porro-prism binoculars with central focusing Binocular telescopes, or binoculars, (also known as field glasses) are two identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects. ... This article does not cite any references or sources. ... A spotting scope is a portable telescope, optimized for the observation of terrestrial objects. ... View through a 4x rifle scope A telescopic sight, commonly referred to as a scope, is a device used to give an accurate point of aim for a firearm. ... An optical theodolite, manufactured in the Soviet Union in 1958 and used for topographic surveying. ... Robert Hookes microscope (1665) - an engineered device used to study living systems. ... This article is about the photographing device. ... Photographic lens One of Canons most popular wide angle lenses - 17-40 f/4 L The zoom lens of the Canon Elph A photographic lens (or more correctly, objective) is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images... Projectors are used for displaying an image on a projection screen or similar surface for the view of an audience. ... Top: The formation of a virtual image using a concave lens. ... Top: The formation of a real image using a convex lens. ... This article or section does not cite its references or sources. ... Not to be confused with censure, censer, or censor. ...

Convex lenses produce an image of an object at infinity at their focus; if the sun is imaged, all the infrared energy incident on the lens is concentrated on the small image. A large lens will concentrate enough energy to heat an inflammable object on which the image falls to burning point. Such lenses, which do not need to be even approximately optically accurate, have been used as burning-glasses for hundreds of years. A modern application is the use of relatively large lenses to concentrate solar energy on relatively small photovoltaic cells, harvesting more energy without the need to use larger, more expensive, cells. Sol redirects here. ... A burning-glass is a large convex lens that can concentrate the suns rays onto a small area, heating up the area and thus resulting in ignition of the surface exposed. ... A photovoltaic cell is a device that turns light into electric energy. ...

Radio astronomy and radar systems often use dielectric lenses, commonly called a lens antenna to refract electromagnetic radiation into a collector antenna. The Square Kilometre Array radio telescope, scheduled to be operational by 2020[1], will employ such lenses to get a collection area nearly 30 times greater than any previous antenna. The Very Large Array, a radio interferometer in New Mexico, USA Radio astronomy is a subfield of astronomy that studies celestial objects in the radio frequency portion of the electromagnetic spectrum. ... For other uses, see Radar (disambiguation). ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... The Square Kilometre Array, once complete will be a radio telescope with a planned collecting area of a square kilometre. ... The 64 meter radio telescope at Parkes Observatory A radio telescope is a form of directional radio antenna most often used in radio astronomy and in tracking and collecting data from satellites and space probes (see Deep Space Network), and are also used in the SETI project. ...

See also

• Aberration in optical systems
• Anti-fogging treatment of optical surfaces
• Axicon
• Back focal plane
• Bokeh
• Corrective lens
• Eyepiece
• F-number
• Fresnel lens
• Gradient index lens
• Gravitational lens
• History of lensmaking
• Lens (anatomy)
• List of lens designs
• Microscope
• Numerical aperture
• Optical coatings
• Optical lens design
• Photochromic lens
• Photographic lens
• Prime lens
• Prism (optics)
• Superlens
• Telescope
• Zoom lens

This article or section is in need of attention from an expert on the subject. ... Anti-fog agents, also known as anti-fogging agents and treatments, prevent the condensation of water on a surface in the form of small droplets which resemble fog. ... There are very few or no other articles that link to this one. ... The cardinal points and the associated cardinal planes are a set of special points and planes in an optical system, which help in the analysis of its paraxial properties. ... The astounding bokeh of a Helios-40 lens A photograph of jonquil flowers with background bokeh Compare a photograph of jonquil flowers with low background bokeh Bokeh (from the Japanese boke ぼけ, blur) is a photographic term describing the subjective aesthetic qualities of out-of-focus areas in an image produced... A bifocal corrective eyeglasses lens A corrective lens is a lens worn on or before the eye, used to treat myopia, hyperopia, astigmatism, and presbyopia. ... A collection of different types of eyepieces. ... A 35mm lens set to f/11, as indicated by the white dot above the f-stop scale on the aperture ring In photography the f-number (focal ratio) expresses the diameter of the diaphragm aperture in terms of the effective focal length of the lens. ... Fresnel Lens displayed in the Musée national de la marine in Paris, France A Fresnel lens is a type of lens invented by Augustin-Jean Fresnel (pronounced fre-NELL in scientific and lighting applications, although often incorrectly pronounced FREZ-nell). ... Gradient index optics is the branch of optics covering optical effects produced by a gradual variation of the refractive index of a material. ... This article or section is in need of attention from an expert on the subject. ... This page is a candidate for speedy deletion. ... Light from a single point of a distant object and light from a single point of a near object being brought to a focus by changing the curvature of the lens. ... Singlet lens Biconvex Plano convex Convex concave Meniscus lens Plano concave Biconcave lens Doublet lens Triplet lens Dialyte lens Celor lens Chevalier lens Wollaston Landscape lens Field lens Fisheye lens Achromatic doublet Apochromatic doublet Cooke Triplet Tessar Lens Petzval lens Double-Gauss Lens Telephoto lens Microscope objective Eyepiece Categories: | | | ... Robert Hookes microscope (1665) - an engineered device used to study living systems. ... Numerical aperture is a technical term of multiple uses: Numerical aperture of optical telecommunication fiber Numerical aperture in microscopy This is a disambiguation page &#8212; a navigational aid which lists other pages that might otherwise share the same title. ... An optical coating is a thin layer of material placed on an optical component such as a lens or mirror which alters the way in which the optic reflects and transmits light. ... Optical lens design is the science/art of calculating the various lens construction parameters (variables) that will meet or at least approach desired performance requirements while staying within required constraint values. ... Photochromic lenses are lenses that darken on exposure to UV radiation. ... Photographic lens One of Canons most popular wide angle lenses - 17-40 f/4 L The zoom lens of the Canon Elph A photographic lens (or more correctly, objective) is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images... This Nikon 35mm wide-angle lens is a small, light-weight and fast prime lens with a maximum aperture of f/2 In film and photography, a prime lens is a photographic lens whose focal length is fixed, as opposed to a zoom lens, which has a variable focal length. ... If a shaft of light entering a prism is sufficiently narrow, a spectrum results. ... A superlens is a lens which is capable of subwavelength imaging. ... This article does not cite any references or sources. ... A Canon Inc. ...

References

General

• Hecht, Eugene (1987). Optics, 2nd ed., Addison Wesley. ISBN 0-201-11609-X.  Chapters 5 & 6.
• Greivenkamp, John E. (2004). Field Guide to Geometrical Optics, SPIE Field Guides vol. FG01, SPIE. ISBN 0-8194-5294-7. 

Footnotes

1. ^ Pliny the Elder, The Natural History (trans. John Bostock) Book XXXVII, Chap. 10.
2. ^ Pliny the Elder, The Natural History (trans. John Bostock) Book XXXVII, Chap. 16
3. ^ Rashed, R. (1990). "A pioneer in anaclastics: Ibn Sahl on burning mirrors and lenses." Isis, 81, 464–491.
4. ^ Greivenkamp, p.14; Hecht §6.1
5. ^ Hecht, § 5.2.3

Pliny the Elder: an imaginative 19th Century portrait. ...

External links

Wikimedia Commons has media related to:

Lens

• History of Optics (audio mp3) by Simon Schaffer, Professor in History and Philosophy of Science at the University of Cambridge, Jim Bennett, Director of the Museum of the History of Science at the University of Oxford and Emily Winterburn, Curator of Astronomy at the National Maritime Museum (recorded by the BBC).
• a chapter from an online textbook on refraction and lenses
• Thin Spherical Lenses on Project PHYSNET.
• Lens article at digitalartform.com
• Thin Lens Java applet
• Article on Ancient Egyptian lenses
• picture of the Ninive rock crystal lens
• Learning by Simulations - Concave and Convex Lenses

Image File history File links Commons-logo. ... The University of Cambridge (often Cambridge University), located in Cambridge, England, is the second-oldest university in the English-speaking world and has a reputation as one of the worlds most prestigious universities. ... The University of Oxford (usually abbreviated as Oxon. ... The National Maritime Museum, Greenwich The National Maritime Museum (NMM) is the leading maritime museum of the United Kingdom, and one of the most important in the world. ... For other uses, see BBC (disambiguation). ...