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Aplanatic
In optics, spherical aberration (SA) is a type of optical aberration, aberration found in optical systems that have elements with spherical surfaces. Lens (optics), Lenses and curved mirrors are prime examples, because this shape is easier to manufacture. Light rays that strike a spherical surface off-centre are refraction, refracted or reflection (physics), reflected more or less than those that strike close to the centre. This deviation reduces the quality of images produced by optical systems. Overview A spherical lens has an Optical aberration#Aberration of elements, i.e. smallest objects at right angles to the axis, aplanatic point (i.e., no spherical aberration) only at a radius that equals the radius of the sphere divided by the index of refraction of the lens material. A typical value of refractive index for crown glass is 1.5 (see List of refractive indices, list), which indicates that only about 43% of the area (67% of diameter) of a spherical lens is useful. It is o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ritchey–Chrétien Telescope
A Ritchey–Chrétien telescope (RCT or simply RC) is a specialized variant of the Cassegrain telescope that has a hyperbolic primary mirror and a hyperbolic secondary mirror designed to eliminate off-axis optical errors (coma). The RCT has a wider field of view free of optical errors compared to a more traditional reflecting telescope configuration. Since the mid 20th century, a majority of large professional research telescopes have been Ritchey–Chrétien configurations; some well-known examples are the Hubble Space Telescope, the Keck telescopes and the ESO Very Large Telescope. History The Ritchey–Chrétien telescope was invented in the early 1910s by American astronomer George Willis Ritchey and French astronomer Henri Chrétien. Ritchey constructed the first successful RCT, which had an aperture diameter of in 1927 (e.g. Ritchey 24-inch reflector). The second RCT was a instrument constructed by Ritchey for the United States Naval Observatory; that telescope ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Aberration
In optics, aberration is a property of optical systems, such as lenses, that causes light to be spread out over some region of space rather than focused to a point. Aberrations cause the image formed by a lens to be blurred or distorted, with the nature of the distortion depending on the type of aberration. Aberration can be defined as a departure of the performance of an optical system from the predictions of paraxial optics. In an imaging system, it occurs when light from one point of an object does not converge into (or does not diverge from) a single point after transmission through the system. Aberrations occur because the simple paraxial theory is not a completely accurate model of the effect of an optical system on light, rather than due to flaws in the optical elements. An image-forming optical system with aberration will produce an image which is not sharp. Makers of optical instruments need to correct optical systems to compensate for aberration. Aberration can be an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Aberration
In optics, aberration is a property of optical systems, such as lenses, that causes light to be spread out over some region of space rather than focused to a point. Aberrations cause the image formed by a lens to be blurred or distorted, with the nature of the distortion depending on the type of aberration. Aberration can be defined as a departure of the performance of an optical system from the predictions of paraxial optics. In an imaging system, it occurs when light from one point of an object does not converge into (or does not diverge from) a single point after transmission through the system. Aberrations occur because the simple paraxial theory is not a completely accurate model of the effect of an optical system on light, rather than due to flaws in the optical elements. An image-forming optical system with aberration will produce an image which is not sharp. Makers of optical instruments need to correct optical systems to compensate for aberration. Aberration can be an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cartesian Oval
In geometry, a Cartesian oval is a plane curve consisting of points that have the same linear combination of distances from two fixed points ( foci). These curves are named after French mathematician René Descartes, who used them in optics. Definition Let and be fixed points in the plane, and let and denote the Euclidean distances from these points to a third variable point . Let and be arbitrary real numbers. Then the Cartesian oval is the locus of points ''S'' satisfying . The two ovals formed by the four equations and are closely related; together they form a quartic plane curve called the ovals of Descartes. Special cases In the equation , when and the resulting shape is an ellipse. In the limiting case in which ''P'' and ''Q'' coincide, the ellipse becomes a circle. When m = a/\!\operatorname(P, Q) it is a limaçon of Pascal. If m = -1 and 0 < a < \operatorname(P, Q) the equation gives a branch of a |
Ray Tracing (physics)
In physics, ray tracing is a method for calculating the path of waves or particles through a system with regions of varying propagation velocity, absorption characteristics, and reflecting surfaces. Under these circumstances, wavefronts may bend, change direction, or reflect off surfaces, complicating analysis. Ray tracing solves the problem by repeatedly advancing idealized narrow beams called '' rays'' through the medium by discrete amounts. Simple problems can be analyzed by propagating a few rays using simple mathematics. More detailed analysis can be performed by using a computer to propagate many rays. When applied to problems of electromagnetic radiation, ray tracing often relies on approximate solutions to Maxwell's equations that are valid as long as the light waves propagate through and around objects whose dimensions are much greater than the light's wavelength. Ray theory does not describe phenomena such as interference and diffraction, which require wave theory (invo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parabolic Reflector
A parabolic (or paraboloid or paraboloidal) reflector (or dish or mirror) is a reflective surface used to collect or project energy such as light, sound, or radio waves. Its shape is part of a circular paraboloid, that is, the surface generated by a parabola revolving around its axis. The parabolic reflector transforms an incoming plane wave travelling along the axis into a spherical wave converging toward the focus. Conversely, a spherical wave generated by a point source placed in the focus is reflected into a plane wave propagating as a collimated beam along the axis. Parabolic reflectors are used to collect energy from a distant source (for example sound waves or incoming star light). Since the principles of reflection are reversible, parabolic reflectors can also be used to collimate radiation from an isotropic source into a parallel beam. In optics, parabolic mirrors are used to gather light in reflecting telescopes and solar furnaces, and project a beam of l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 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. Maksutov telescopes have been sold on the ama ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hubble Space Telescope
The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versatile, renowned both as a vital research tool and as a public relations boon for astronomy. The Hubble telescope is named after astronomer Edwin Hubble and is one of NASA's Great Observatories. The Space Telescope Science Institute (STScI) selects Hubble's targets and processes the resulting data, while the Goddard Space Flight Center (GSFC) controls the spacecraft. Hubble features a mirror, and its five main instruments observe in the ultraviolet, visible, and near-infrared regions of the electromagnetic spectrum. Hubble's orbit outside the distortion of Earth's atmosphere allows it to capture extremely high-resolution images with substantially lower background light than ground-based telescopes. It has recorded some of the most de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Achromatic Lens
An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration. Achromatic lenses are corrected to bring two wavelengths (typically red and blue) into focus on the same plane. The most common type of achromat is the achromatic doublet, which is composed of two individual lenses made from glasses with different amounts of dispersion. Typically, one element is a negative (concave) element made out of flint glass such as F2, which has relatively high dispersion, and the other is a positive (convex) element made of crown glass such as BK7, which has lower dispersion. The lens elements are mounted next to each other, often cemented together, and shaped so that the chromatic aberration of one is counterbalanced by that of the other. In the most common type (shown), the positive power of the crown lens element is not quite equalled by the negative power of the flint lens element. Together they form a weak positive lens that will ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gizmodo
''Gizmodo'' ( ) is a design, technology, science and science fiction website. It was originally launched as part of the Gawker Media network run by Nick Denton, and runs on the Kinja platform. ''Gizmodo'' also includes the subsite '' io9'', which focuses on science fiction and futurism. ''Gizmodo'' is now part of G/O Media, owned by private equity firm Great Hill Partners. History The blog, launched in 2002, was originally edited by Peter Rojas, who was later recruited by Weblogs, Inc. to launch their similar technology blog, ''Engadget''. By mid-2004, ''Gizmodo'' and ''Gawker'' together were bringing in revenue of approximately $6,500 per month. Gizmodo then launched in other locations: *In 2005, VNU and Gawker Media formed an alliance to republish ''Gizmodo'' across Europe, with VNU translating the content into French, German, Dutch, Spanish, Italian and Portuguese, and adding local European-interest material. *In 2006, ''Gizmodo Japan'' was launched by Mediagene, wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monterrey Institute Of Technology And Higher Education
Instituto Tecnológico y de Estudios Superiores de Monterrey (ITESM) ( en, Monterrey Institute of Technology and Higher Education), also known as Tecnológico de Monterrey or just Tec, is a secular and coeducational private university based in Monterrey, Mexico, which has grown to include 35 campuses throughout the country. One of only 45 universities in the World to be ranked with 5 QS Stars, it is widely recognized as one of the most prestigious universities in Latin America. Founded in 1943 by Eugenio Garza Sada, an MIT-educated industrialist, the university has always had close links with the Mexican business elite; as of 2019, it is the 15th university in the world with the highest number of billionaire alumni according to the '' Times Higher Education'' and the only university in Latin America to appear in the ranking. ITESM is also known as being the first university to be connected to the Internet in Ibero-America,The first connection from Spain was completed i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Autonomous University Of Mexico
The National Autonomous University of Mexico ( es, Universidad Nacional Autónoma de México, UNAM) is a public research university in Mexico. It is consistently ranked as one of the best universities in Latin America, where it's also the biggest in terms of enrollment. A portion of UNAM's main campus in Mexico City, known as '' Ciudad Universitaria'' (University City), is a UNESCO World Heritage site that was designed by some of Mexico's best-known architects of the 20th century and hosted the 1968 Summer Olympic Games. Murals in the main campus were painted by some of the most recognized artists in Mexican history, such as Diego Rivera and David Alfaro Siqueiros. With acceptance rates usually below 10%, and its research, especially in Artificial Intelligence, being recognized by UNESCO as one of the most impactful globally, UNAM is known for its high quality research and educational level. All Mexican Nobel laureates are either alumni or faculty of UNAM. UNAM was founded, i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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