Copyright © Philip M. Parker, INSEAD. Terms of Use.
Definition: LENSES |
LENSESPlural1. Of Lens |
Date "LENSES" was first used in popular English literature: sometime before 1844. (references) |
| Domain | Definition |
Health | Pieces of glass or other transparent materials used for magnification or increased visual acuity. (references) |
Source: compiled by the editor from various references; see credits. | |
(From Wikipedia, the free Encyclopedia)
This is about the optical device. For other uses, see Lens (disambiguation).
A lens is a device for either concentrating or diverging light, usually formed from a piece of shaped glass. Analogous devices used with other types of electromagnetic radiation are also called lenses: for instance, a microwave lens can be made from paraffin wax.
In its usual form, a lens consists of a slab of glass or other optically transparent material (such as perspex) with two shaped surfaces of a particular curvature. It is the refractive index of the lens material and the curvature of the two surfaces that give a particular lens its particular properties. A lens works by refracting (bending) the light that passes through it, in a similar manner to a prism.
Lens construction
The most common type of lenses are spherical lenses, which are formed from surfaces that have spherical curvature, that is, the front and back surfaces of the lens can be imagined to be part of the surface of two spheres of given radii, R1 and R2, which are called the radius of curvature of each surface. The sign of R1 gives the shape of the front surface of the lens: if R1 is positive, the surface is convex (bulging outwards from the lens). If R1 is negative, the front surface is concave (bulging into the lens). If R1 is infinite, the surface is flat, or has zero curvature, and is said to be plane. The same is true for the back surface of the lens, except that the sign conversion is reversed: if R2 is positive, it is concave, and if R2 is negative,the back surface is convex. 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.
Lens are classified by the curvature of these two surfaces. A lens is biconvex if both surfaces are convex, likewise, a lens with two concave surfaces is biconcave. If one of the surfaces is flat, the lens is termed plano-convex or plano-concave depending on the curvature of the other surface. A lens with one convex and one concave side is termed convex-concave, and in this case if both curvatures are equal it is a meniscus lens.
If the lens is biconvex or plano-convex, a collimated or parallel beam of light passing along the lens axis and 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.
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.
If the lens is convex-concave, whether it is converging or diverging depends on the relative curvatures of the two surfaces. If the curvatures are equal (a meniscus lens), then the beam is neither converged or diverged.
The value of the focal length f for a particular lens can be calculated from the lensmaker's equation:
where n is the refractive index of the lens material and d is the distance along the lens axis between the two surfaces (known as the thickness of the lens). If d is small compared to R1 and R2, then the thin lens assumption can be made, and f can be estimated as:
- ,
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 power of the lens, and so meniscus lenses are said to have zero power. Lens power is measured in dioptres, which have units of inverse meters (m-1).
- .
Lenses are also reciprocal; i.e. they have the same focal length when light travels from the front to the back as when light goes from the back to the front (although other properties of the lens, such as the aberration [see below] are not necessarily the same in both directions).
Imaging properties
As mentioned above, a positive or converging lens 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 light) is focused to an image at the focal point of the lens. In the later, an object at the focal length distance from the lens is imaged at infinity.
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 they are found 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.
- .
Note that if S1 < f, S2 becomes negative, and the image is apparently positioned in front of the lens. 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.
The magnification of the lens is given by:
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=∞, we have 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 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.
Aberrations
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 minimised.
There are several different types of aberration. Spherical aberration is caused 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, which are complex to make and often extrememly expensive. 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.
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, if follows that different wavelengths of light will be focused to different positions. Chromatic aberration of a lens is seen as fringes of color 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 developement of the optical microscope.
Other kinds of aberration include coma, field curvature, barrel and pincushion distortion, and astigmatism.
Multiple lenses
Lenses may be combined to form more complex optical systems. The simplest case is when lenses are placed in contact: if the lenses of focal lengths f1 and f2 are "thin", the combined focal length F of the lenses can be calculated from:
Since 1/f is the power of a lens, it can be seen that the powers of thin lenses in contact are additive.
- .
Uses of lenses
One important use of lenses is as a prosthetic for the correction of visual impairments such as myopia and farsightedness. See corrective lens, contact lens, eyeglasses.
Another use is in imaging systems such as telescopes, microscopes, and cameras.
See also
- Aberration in optical systems
- Photographic lens
- F-number
- Numerical aperture
- Telescope
- Microscope
- Fresnel lens.
- Lens coatings
- Gradient index lens
- History of lensmaking
- Zoom lens
Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Lens."
Crosswords: LENSES |
| English words defined with "LENSES": Abbe condenser, Achromatic lens, Altiscope, aphakic ♦ bacon, bicylindrical, bridge ♦ compound lens, Compound microscope, Cosmorama ♦ Din Land, Dioptrics ♦ Edwin Herbert Land, enlarged, Erecting eyepiece, exaggerated, eyeglasses, eyepiece ♦ Field lens, Fresnel lens ♦ glasses ♦ Holophote ♦ jeweler's glass ♦ land ♦ magnified, Microphotograph ♦ nosepiece ♦ Object glass, objective, ocular, Opera glass, optical glass ♦ prescription ♦ Reflected vision, Refracted vision, Roger Bacon ♦ Scioptics, specs, spectacles, Stereomonoscope ♦ Terrestrial telescope. (references) |
| Specialty definitions using "LENSES": Contact Lenses, Extended-Wear, Contact Lenses, Hydrophilic ♦ glass for corrective lenses ♦ Lenses, Intraocular ♦ zoom lenses. (references) |
| Domain | Usage | |
Screenplays | Ok. First, get some contact lenses, cause those joints look like they could pick up cable (Men in Black II; writing credit: Lowell Cunningham; Robert Gordon) Well they'd be worth more if the lenses were intact (Star Trek IV: The Voyage Home; writing credit: Leonard Nimoy; Harve Bennett) | |
Source: compiled by the editor from various references; see credits. | ||
| Domain | Title | ||
References |
| ||
Books |
| ||
Periodicals |
| ||
Theater & Movies | |||
Music |
| ||
High Tech |
| ||
Source: compiled by the editor from various references; see credits. | |||
| Thumbnail | Description & Credit | Thumbnail | Description & Credit |
 | The automated inspection system compares pictures of each bird as viewed through a red filter and a green filter, to spot defective chickens. Here, agricultural engineer Yud-Ren Chen places a green filter on one of the lenses of the computerized, four-camera subsystem. P. Credit: USDA ARS News; photo by Keith Weller.. |  | A researcher prepares extracts from normal eye lenses and cataracts for scientific analysis. Credit: National Eye Institute, National Institutes of Health. |
 | A phoroptor measures the prescription for corrective lenses. Credit: National Eye Institute, National Institutes of Health. |  | Lenses placed in a trial frame help determine an eyeglass prescription. Credit: National Eye Institute, National Institutes of Health. |
 | Checking Of Goggle Lenses : School Of Aviation Medicine. Credit: National Library of Medicine. |  | Fitting the right lenses in his spectacles ... means he can once more see the world about him. / WHO p. Credit: National Library of Medicine; photo by N. Willard.. |
Source: pictures compiled by the editor from various references; see picture credits. | |||
 |
| "Fairy Dust" by Lynn Cummings Commentary: "Some digital lenses, in the right lighting, will render the effect of a star filter." |
Source: photographs selected by the editor, with permission from the photographers. |
| Subject | Topic | Quote |
Health | Frequent changes in your eyeglasses or contact lenses. (references) | |
These lenses let the doctor focus on the inner surfaces of the urinary tract. (references) | ||
Glasses or contact lenses are designed to compensate for the eye's imperfections. (references) | ||
Business | Pakistan imports high-tech, sophisticated products such as diagnostic equipment, electro-medical apparatus, laboratory equipment, and optical instruments and lenses from various sources such as the U.S., South Korea, Singapore, Germany, United Kingdom and Japan. (references) | |
Economic History | Ireland | A broad range of products are manufactured in Ireland including drug-delivery pumps, vascular and endoscopic devices, orthopaedic implants, ostomy products, pacemakers, diagnostic kits and contact lenses. (references) |
Korea | Products that present the best export prospects for U.S. exporters include various high-tech medical products, including sterilizers, rehabilitation equipment, respiration equipment, orthopedic joints, diagnostic ultrasound scanners, magnetic resonance imaging systems, patient monitors, computer tomography scanners, catheters, artificial kidneys and dialysis machines, suture, suture needles, general surgical instruments, operation tables, ophthalmic equipment, endoscopes, intraocular lenses, artificial heart valves and dental equipment and supplies. (references) | |
Source: compiled by the editor from ICON Group International, Inc.; see credits. | ||
| "LENSES" is generally used as a noun (plural) -- approximately 94.13% of the time. "LENSES" is used about 375 times out of a sample of 100 million words spoken or written in English. Its rank is based on over 700,000 words used in the English language. Some parts-of-speech are not covered due to the samples used by the British National Corpus. (note: percents less than one-hundredth of one percent have been omitted) |
| Parts of Speech | Percent | Usage per 100 Million Words | Rank in English |
| Noun (plural) | 94.13% | 353 | 15,179 |
| Lexical Verb (-s form) | 5.6% | 21 | 76,261 |
| Noun (proper) | 0.27% | 1 | 339,140 |
| Total | 100.00% | 375 | N/A |
Source: compiled by the editor from several corpora; see credits.
Expressions using "LENSES": camera mirror lenses ♦ cataract lenses ♦ contact lenses ♦ disposable contact lenses ♦ glass for corrective lenses ♦ mirror lenses ♦ wear contact lenses ♦ zoom lenses. Additional references. | |
| Hypenated Usage | |
Ending with "LENSES": contact-lenses, seeing-lenses, sun-lenses, zoom-lenses. | |
| Source: compiled by the editor from various references; see credits. | |
| Language | Translations for "LENSES"; alternative meanings/domain in parentheses. | |
Albanian | lente kontakti (contact lenses, contacts). (various references) | |
Arabic | عدسات لاصقة (contact lenses). (various references) | |
Bulgarian | контактни ленти (contact lenses). (various references) | |
Chinese | 透镜 (lens). (various references) | |
Czech | kontaktní èoèky (contact lenses). (various references) | |
Danish | sammenkitning af linser (cementing of lenses), blok (block, pad), brilleglas til korrektion af synsfejl (opthalmic lenses), glas til korrektionsbriller (glass for corrective lenses), indfattede linser (mounted lenses), kontaktlinser (contact lenses), objektiv (give an image of the object observed, objective, objective containing one or more lenses which, when directed optical systems towards an object), beskyttelsesbriller (goggles, protective goggles, protective lenses, safety goggles, safety spectacles), saafremt jordartens kornfordeling er saaledes,at der er tilstraekkelig smaa porer under isfrie forhold,vil der finde en betydelig vandtilstroemning sted,og der vil dannes horisontale islag eller islinser (if the particle-size distribution of the soil is such that there are sufficient small pores in an ice-free condition, then considerable migration of water takes place and horizontal layers or lenses of ice are formed), udgifter til vedligeholdelse af kontaktlinser (cost of maintaining contact lenses), staerbrille (cataract lenses), supplerende korrektionslinser (additional corrective lenses), supplerende linser (additional lenses), system af elektromagnetiske linser (system consisting of electromagnetic lenses), system af elektrostatiske linser (system consisting of electro-static lenses), traadkors til optiske instrumenter (hairline for telescope lenses), paa brudfladen i deformerede produkter ses fnug som lyse linser,hvis diameter ligger mellem 1 mm og nogle centimeter (the diameter of which varies from 1 mm to several centimetres, the flakes show up on the fracture surface of worked products as pale lenses). (various references) | |
Dutch | contactlenzen (contact lenses). (various references) | |
Finnish | piilolasit (contact lenses). (various references) | |
French | lentille additionnelle (additional lenses, auxiliary lens, supplementary lens), lentilles de contact (contact lenses, lens), lentilles montées (mounted lenses), les flocons apparaissent sur la cassure des produits corroyés comme des lentilles claires (the flakes show up on the fracture surface of worked products as pale lenses), lunettes pour aphaques (cataract lenses), objectif à miroir (camera mirror lenses, mirror lenses), bloc (block of lenses), cimentation de lentilles (cementing of lenses), collage de lentilles (cementing of lenses), fourniture de verres de contact (supply of contact lenses), frais d'entretien des lentilles de contact (cost of maintaining contact lenses), éléments correcteurs supplémentaires (additional corrective lenses), objectif (lems, lens), zoum (zoom lenses), objectifs interchangeables (interchangeable lenses), prescription de lentilles correctives (prescribing of corrective lenses), réticule d'instruments d'optique (hairline for telescope lenses), si la granularité du sol est telle qu'il y a suffisamment de petits pores en l'absence de glace,une importante quantité d'eau migre et des couches ou lentilles horizontales de glace se forment (then considerable migration of water takes place and horizontal layers or lenses of ice are formed), système de lentilles électromagnétiques (system consisting of electromagnetic lenses), système de lentilles électrostatiques (system consisting of electro-static lenses), verre de contact (contact lenses), verre de lunetterie médicale (glass for corrective lenses), verres de contact (contact lenses), verres de lunetterie médicale (opthalmic lenses), mise au point de lentilles correctives (fitting of corrective lenses). (various references) | |
German | Linsen (copy, peek, peep). (various references) | |
Greek | γυαλί για ιατρικά ματογυάλια (glass for corrective lenses), οι νιφάδες εμφανίζονται στην επιφάνεια της ρωγμής κατεργασμένων προϊόντων ως ανοικτόχρωμοι φακοί,η διάμετρος των οποίων ποικίλει απο 1 mm μ (the flakes show up on the fracture surface of worked products as pale lenses), Αν η κοκκομετρική σύνθεση του εδάφους είναι τέτοια ώστε να υπάρχουν αρκετοί μικροί πόροι πριν από την εμφάνιση πάγου,μια σημαντική ποσότητ (then considerable migration of water takes place and horizontal layers or lenses of ice are formed), αντικειμενικός φακός (give an image of the object observed, objective containing one or more lenses which, when directed optical systems towards an object), φακοί επαφής (contact lenses), προμήθεια φακών επαφής (supply of contact lenses), προσθετικός φακός (additional lenses), δικτυωτό νήμα οργάνων οπτικής (hairline for telescope lenses), κονιαματοποίηση φακών (cementing of lenses), γυαλιά οφθαλμιατρικής χρήσης (opthalmic lenses), γυαλιά επαφής (contact lenses), συμπληρωματικά διορθωτικά στοιχεία της όρασης (additional corrective lenses), συναρμολογημένοι φακοί (mounted lenses), σύστημα ηλεκτρομαγνητικών φακών (system consisting of electromagnetic lenses), σύστημα ηλεκτροστατικών φακών (system consisting of electro-static lenses), μπλόκ γυαλιού (block, block of lenses). (various references) | |
Hungarian | kontaktlencse (contact lens, contact lenses, contacts), lencserendszer-készlet (battery of lenses). (various references) | |
Italian | lente addizionale (additional lenses), lenti da contatto (contact lenses), lenti montate (mounted lenses), occhiali per afachici (cataract lenses), elementi correttori supplementari (additional corrective lenses), I fiocchi si presentano con aspetto lenticolare chiaro con diametri da 1 mm ad alcuni centimetri sulla superficie di frattura dei manufatti lavorati plasticamente (the diameter of which varies from 1 mm to several centimetres, the flakes show up on the fracture surface of worked products as pale lenses), Incollaggio delle lenti (cementing of lenses), blocco di lenti (block, block of lenses), obiettivo (lens, objective, target, unbiased), vetro per occhialeria medica (glass for corrective lenses), reticelle per strumenti d'ottica (hairline for telescope lenses), se nella componente granulometrica del terreno e diffusa una forte quantita di pori non contenenti ghiaccio,viene assorbita una rilevante quantita di acqua con formazione di strati o lenti orizzontali di ghiaccio (if the particle-size distribution of the soil is such that there are sufficient small pores in an ice-free condition, then considerable migration of water takes place and horizontal layers or lenses of ice are formed), sistema di lenti elettromagnetiche (system consisting of electromagnetic lenses), sistema di lenti elettrostatiche (system consisting of electro-static lenses), spese di manutenzione delle lenti a contatto (cost of maintaining contact lenses), vetri di occhialeria medica (opthalmic lenses), obiettivi intercambiabili (interchangeable lenses). (various references) | |
Japanese Kanji | 近眼鏡 (corrective lenses for myopia). (various references) | |
Japanese Katakana | きんがんきょう (corrective lenses for myopia). (various references) | |
Korean | 렌즈 (lens). (various references) | |
Pig Latin | enseslay.(various references) | |
Portuguese | lentes. (various references) | |
Portuguese Brazilian | lentes. (various references) | |
Russian | контактные линзы (contact lenses), контактные линза (contact lens, contact lenses). (various references) | |
Serbo-Croatian | kontaktna sočiva (contact lenses). (various references) | |
Spanish | lentes (glasses, specs, spectacles). (various references) | |
Swedish | linser. (various references) | |
Turkish | lensler (contact lenses), lens takmak (wear contact lenses), lens kullanmak (wear contact lenses), tek kullanımlık lensler (disposable contact lenses), kullanılıp atılabilir lensler (disposable contact lenses). (various references) | |
| Source: compiled by the editor from various translation references. | ||
Derivations | |
Words ending with "LENSES": flenses. (additional references) | |
| |
"LENSES" is suggested in spellcheckers for the following: Elsnet, Glenshesk, Leesas, lendes, Lenesta, lenez, lenfest, lennies, Lense, lensed, Lensi, leses, Lesne, Lesnes, Lesnik, Penskes. (additional references) | |
| Source: compiled by the editor, based on several corpora (additional references). | |
| # of Phoneme Matches | Pronunciation | Word(s) rhyming with "LENSES" (pronounced le"nzuz) |
| 4 | -n z u z | bronzes, extravaganzas, joneses, stanzas, summonses. |
| 3 | -z u z | accuses, advertises, advises, agonizes, amazes, amuses, analyzes, apologizes, appraises, arises, arouses, authorizes, confuses, blazes, bowses, breezes, bruises, brutalizes, buzzes, capitalizes, categorizes, causes, characterizes, chastises, cheeses, chooses, clauses, closes, composes, comprises, compromises, criticizes, cruises, decomposes, demilitarizes, despises, devises, Dieses, diffuses, discloses, diseases, disguises, disposes, dozes, dramatizes, eases, emphasizes, energizes, enfranchises, enterprises, epitomizes, espouses, excises, exercises, exposes, fantasizes, fertilizes, forecloses, formalizes, franchises, freezes, fuses, fuzes, galvanizes, gazes, glazes, guises, hoses, humanizes, idolizes, immortalizes, immunizes, imposes, infuses, institutionalizes, ironizes, jeopardizes, legitimizes, Lollapaloozas, loses, marginalizes, materializes, maximizes, mazes, minimizes, mises, misuses, monopolizes, muses, neutralizes, noises, noses, oozes, opposes, organizes, oversizes, paralyzes, pauses, penalizes, personalizes, phases, phrases, Plazas, pleases, polarizes, polymerizes, poses, praises, pressurizes, presupposes, primroses, prioritizes, prizes, proposes, quizzes, raises, realizes, reanalyses, recognizes, refuses, reorganizes, revises, rhapsodizes, rises, roses, ruses, satirizes, scrutinizes, seizes, sensationalizes, sizes, sneezes, specializes, squeezes, stabilizes, sterilizes, storehouses, subsidizes, summarizes, supervises, supposes, surmises, surprises, symbolizes, sympathizes, tantalizes, teases, terrorizes, theorizes, trivializes, utilizes, visas, warehouses, wheezes, whizzes. |
Source: compiled by the editor (additional references); see credits. | ||
Scrabble® Enable2K-Verified Anagrams | |
Direct Anagrams: lessen. | |
| Words within the letters "e-e-l-n-s-s" | |
-1 letter: lenes, lense, seels, sense. | |
-2 letters: eels, else, eses, lees, lens, less, ness, seel, seen, sees, sels, sene. | |
-3 letters: eel, els, ens, ess, lee, nee, see, sel, sen. | |
-4 letters: el, en, es, ne. | |
| Words containing the letters "e-e-l-n-s-s" | |
+1 letter: endless, enisles, ensiles, flenses, lessens, nestles, netless, seniles, spleens. | |
+2 letters: blueness, boneless, cleanses, encloses, enolases, enslaves, evilness, fellness, fernless, flensers, fresnels, glegness, haleness, idleness, keelsons, lameness, lateness, leanness, lensless, lessened, lessoned, lewdness, licenses, likeness, lineless, linseeds, liveness, loneness, maleness, maneless, nameless, neckless, needless, nestlers, newsless, noblesse, noseless, noteless, paleness, realness, reinless, salesmen, selenous, selfness, senseful, sensible, setlines, silences, sleekens, snellest, soleness, tentless, toneless, tuneless, unsteels, veinless, ventless, vileness, wellness, wineless, zoneless. | |
| Source: compiled by the editor from various references; see credits. SCRABBLE® is a registered trademark. All intellectual property rights in and to the game are owned in the U.S.A and Canada by Hasbro Inc., and throughout the rest of the world by J.W. Spear & Sons Limited of Maidenhead, Berkshire, England, a subsidiary of Mattel Inc. Mattel and Spear are not affiliated with Hasbro. | |
| 1. Definition 2. Crosswords 3. Usage: Modern 4. Usage: Commercial | 5. Images: Slideshow 6. Images: Photo Album 7. Images: Digital Art 8. Quotations: Non-fiction | 9. Usage Frequency 10. Expressions 11. Translations: Modern 12. Derivations | 13. Rhymes 14. Anagrams 15. Bibliography |
Copyright © Philip M. Parker, INSEAD. Terms of Use.
