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Meniscus Corrector
A MENISCUS CORRECTOR is a negative meniscus lens that is used to correct spherical aberration in image-forming optical systems such as catadioptric telescopes . It works by having the equal but opposite spherical aberration of the objective it is designed to correct (usually a spherical mirror ). CONTENTS * 1 Types * 2 Invention * 3 See also * 4 References * 5 Further reading TYPESMeniscus correctors are used as full aperture correctors, most commonly in a Maksutov telescope sub type called the Gregory or “spot” Maksutov–Cassegrain telescope . They are also used in the Bouwers meniscus telescope . There are Maksutov variations that use the same principle but place the meniscus lens as a sub-aperture corrector near the focus of the objective
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Dennis Gabor
DENNIS GABOR CBE , FRS (/ˈɡɑːbɔːr, ɡəˈbɔːr/ ; Hungarian : Gábor Dénes; 5 June 1900 – 9 February 1979) was a Hungarian -British electrical engineer and physicist , most notable for inventing holography , for which he later received the 1971 Nobel Prize in Physics
Physics
. CONTENTS * 1 Life and career * 2 Awards and honors * 2.1 In popular culture * 3 References * 4 External links LIFE AND CAREERGabor was born as GüNSZBERG DéNES, into a Jewish family in Budapest , Hungary. In 1918, his family converted to Lutheranism
Lutheranism
. Dennis was the first-born son of Günszberg Bernát and Jakobovits Adél. Despite having a religious background, religion played a minor role in his later life and he considered himself agnostic. In 1902, the family received permission to change their surname from Günszberg to Gábor. He served with the Hungarian artillery in northern Italy during World War I
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Schmidt Camera
A SCHMIDT CAMERA, also referred to as the SCHMIDT TELESCOPE, is a catadioptric astrophotographic telescope designed to provide wide fields of view with limited aberrations . The design was invented by Bernhard Schmidt in 1930. Some notable examples are the Samuel Oschin telescope (formerly Palomar Schmidt), the UK Schmidt Telescope and the ESO Schmidt; these provided the major source of all-sky photographic imaging from 1950 until 2000, when electronic detectors took over. A recent example is the Kepler spacecraft exoplanet finder. Other related designs are the Wright Camera and Lurie–Houghton telescope
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Spherical Aberration
Tilt Spherical aberration Astigmatism Coma Distortion Petzval field curvature Chromatic aberration
Chromatic aberration
SPHERICAL ABERRATION is an optical effect observed in an optical device (lens , mirror , etc.) that occurs due to the increased refraction of light rays when they strike a lens or a reflection of light rays when they strike a mirror near its edge, in comparison with those that strike nearer the centre. It signifies a deviation of the device from the norm, i.e., it results in an imperfection of the produced image. On top is a depiction of a perfect lens without spherical aberration: all incoming rays are focused in the focal point . The bottom example depicts a real lens with spherical surfaces, which produces spherical aberration: The different rays do not meet after the lens in one focal point
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Coma (optics)
Tilt Spherical aberration Astigmatism Coma Distortion Petzval field curvature Chromatic aberration Coma of a single lens In optics (especially telescopes ), the COMA, or COMATIC ABERRATION, in an optical system refers to aberration inherent to certain optical designs or due to imperfection in the lens or other components that results in off-axis point sources such as stars appearing distorted, appearing to have a tail (coma ) like a comet . Specifically, coma is defined as a variation in magnification over the entrance pupil . In refractive or diffractive optical systems, especially those imaging a wide spectral range, coma can be a function of wavelength , in which case it is a form of chromatic aberration
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Astigmatism (optical Systems)
Tilt Spherical aberration
Spherical aberration
Astigmatism Coma Distortion Petzval field curvature Chromatic aberration
Chromatic aberration
An optical system with ASTIGMATISM is one where rays that propagate in two perpendicular planes have different foci . If an optical system with astigmatism is used to form an image of a cross , the vertical and horizontal lines will be in sharp focus at two different distances. The term comes from the Greek α- (a-) meaning "without" and στίγμα (stigma), "a mark, spot, puncture"
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Special
SPECIAL or SPECIALS may refer to: CONTENTS * 1 Music * 2 Film and television * 3 Other uses * 4 See also MUSIC * Special (album) , a 1992 album by Vesta Williams * "Special" (Garbage song) , 1998 * "Special" (Mew song) , 2005 * "Special" (Stephen Lynch song) , 2000 * The Specials
The Specials
, a British band * "Special", a song by Violent Femmes on The Blind Leading the Naked * "Special", a song on
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Chromatic Aberration
Tilt Spherical aberration
Spherical aberration
Astigmatism Coma Distortion Petzval field curvature Chromatic aberration
Chromatic aberration
Photographic example showing high quality lens (top) compared to lower quality model exhibiting lateral chromatic aberration (seen as a blur and a rainbow edge in areas of contrast.) In optics , CHROMATIC ABERRATION (abbreviated CA; also called CHROMATIC DISTORTION and SPHEROCHROMATISM) is an effect resulting from dispersion in which there is a failure of a lens to focus all colors to the same convergence point. It occurs because lenses have different refractive indices for different wavelengths of light . The refractive index of transparent materials decreases with increasing wavelength in degrees unique to each
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Mangin Mirror
In optics , a MANGIN MIRROR is a negative meniscus lens with the reflective surface on the rear side of the glass forming a curved mirror that reflects light without spherical aberration . This reflector was invented in 1876 by a French officer Alphonse Mangin as an improved catadioptric reflector for search lights and is also used in other optical devices. CONTENTS * 1 Description * 2 Applications * 3 Notes * 4 External links DESCRIPTIONThe Mangin mirror's construction consists of a concave (negative meniscus ) lens made of crown glass with spherical surfaces of different radii with the reflective coating on the shallower rear surface. The spherical aberration normally produced by the simple spherical mirror surface is canceled out by the opposite spherical aberration produced by the light traveling through the negative lens. Since light passes through the glass twice, the overall system acts like a triplet lens
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Ludwig Schupmann
LUDWIG IGNAZ SCHUPMANN (23 January 1851 in Geseke (Westphalia ), Germany – 2 October 1920 also in Geseke ) was a German professor of architecture and an optical designer. He is principally remembered today for his Medial and Brachymedial telescopes, types of catadioptric reflecting-refracting telescopes with Mangin mirrors that eliminate chromatic aberrations while using common optical glasses. Used in early lunar studies, they are used now in double-star work
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Spherical Mirror
A CURVED MIRROR is a mirror with a curved reflecting surface. The surface may be either convex (bulging outwards) or concave (bulging inwards). Most curved mirrors have surfaces that are shaped like part of a sphere , but other shapes are sometimes used in optical devices. The most common non-spherical type are parabolic reflectors , found in optical devices such as reflecting telescopes that need to image distant objects, since spherical mirror systems, like spherical lenses , suffer from spherical aberration . Distorting mirrors are used for entertainment. They have convex and concave regions that produce deliberately distorted images
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Objective (optics)
In optical engineering , the OBJECTIVE is the optical element that gathers light from the object being observed and focuses the light rays to produce a real image . Objectives can be a single lens or mirror , or combinations of several optical elements. They are used in microscopes , telescopes , cameras , slide projectors , CD players and many other optical instruments. Objectives are also called OBJECT LENSES, OBJECT GLASSES, or OBJECTIVE GLASSES. CONTENTS* 1 Types * 1.1 Microscope
Microscope
* 1.2 Photography and imaging * 1.3 Telescope
Telescope
* 2 See also * 3 References TYPESMICROSCOPEThe objective lens of a microscope is the one at the bottom near the sample. At its simplest, it is a very high-powered magnifying glass , with very short focal length . This is brought very close to the specimen being examined so that the light from the specimen comes to a focus inside the microscope tube
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Image-forming Optical System
In optics , an IMAGE-FORMING OPTICAL SYSTEM is a system capable of being used for imaging . The diameter of the aperture of the main objective is a common criterion for comparison among optical systems, such as large telescopes. The two traditional systems are mirror -systems (catoptrics ) and lens -systems (dioptrics ), although in the late twentieth century, optical fiber was introduced. Catoptrics and dioptrics have a focal point , while optical fiber transfers an image from one plane to another without an optical focus. Isaac Newton is reported to have designed what he called a catadioptrical phantasmagoria, which can be interpreted to mean an elaborate structure of both mirrors and lenses. Catoptrics and optical fiber have no chromatic aberration , while dioptrics need to have this error corrected. Newton believed that such correction was impossible, because he thought the path of the light depended only on its color
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Argunov–Cassegrain Telescope
The ARGUNOV CASSEGRAIN TELESCOPE is a catadioptric telescope design first introduced in 1972 by P. P. Argunov. All optics are spherical , and the classical Cassegrain secondary mirror is replaced by a sub-aperture secondary corrector group consisting of three air-spaced elements, two lenses and a Mangin mirror
Mangin mirror
(the element farthest from the primary mirror). Argunov systems only employ spherical surfaces and avoid the practical difficulties of making and testing aspheres . However, this seeming benefit is marginal, as it is almost as difficult to make a true, zone-free sphere of precise radius of curvature as it is to make an asphere of equivalent precision. Also since multiple surfaces are involved, creating a design with good aberration correction can be very complex. SEE ALSO * Klevtsov–Cassegrain telescope
Klevtsov–Cassegrain telescope
* List of telescope types REFERENCES * P. P
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Maksutov Telescope
The MAKSUTOV (also called a "MAK") is a catadioptric telescope design that combines a spherical mirror with a weakly negative meniscus lens in a design that takes advantage of all the surfaces being nearly "spherically symmetrical". The negative lens is usually full diameter and placed at the entrance pupil of the telescope (commonly called a "corrector plate" or "meniscus corrector shell "). The design corrects the problems of off-axis aberrations such as coma found in reflecting telescopes while also correcting chromatic aberration . It was patented in 1941 by Russian optician Dmitri Dmitrievich Maksutov . Maksutov based his design on the idea behind the Schmidt camera
Schmidt camera
of using the spherical errors of a negative lens to correct the opposite errors in a spherical primary mirror . The design is most commonly seen in a Cassegrain variation, with an integrated secondary, that can use all-spherical elements, thereby simplifying fabrication
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Klevtsov–Cassegrain Telescope
The KLEVTSOV–CASSEGRAIN TELESCOPE is a type of catadioptric Cassegrain telescope that uses a spherical primary mirror and a sub-aperture secondary corrector group composed of a small lens and a Mangin mirror . CONTENTS * 1 Design * 2 See also * 3 References * 4 External links DESIGN Light path in a Klevtsov-Cassegrain reflector telescope In the Klevtsov-Cassegrain all of the optical surfaces are spherical or near-spherical. The secondary Mangin mirror (M 2 ) and the meniscus corrector (C) are held in place by a spider vane and the front of the telescope tube is otherwise open. These types of telescopes have the disadvantage of spider to hold the corrector causing diffraction artifacts and, since multiple surfaces are involved, achieving good aberration correction can be very complex. This design was originally envisaged by G. I. Popov with a practical implementation by Yuri A. Klevtsov
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