Magnifying glass

A magnifying glass (called a hand lens in laboratory contexts) is a convex lens that is used to produce a magnified image of an object. The lens is usually mounted in a frame with a handle (see image). A magnifying glass can be used to focus light, such as to concentrate the sun's radiation to create a hot spot at the focus for fire starting.

A sheet magnifier consists of many very narrow concentric ring-shaped lenses, such that the combination acts as a single lens but is much thinner. This arrangement is known as a Fresnel lens.

The magnifying glass is an icon of detective fiction, particularly that of Sherlock Holmes.

Magnifying-glass-green-brass
Text seen through a magnifying glass
Magnifying-fresnel-lens
A plastic Fresnel lens sold as a TV-screen magnifier
Magnification power of a loupe
Diagram of a single lens magnifying glass.

History

"The evidence indicates that the use of lenses was widespread throughout the Middle East and the Mediterranean basin over several millennia".[1] The earliest explicit written evidence of a magnifying device is a joke in Aristophanes's The Clouds[2] from 424 BC, where magnifying lenses to start kindling were sold in a pharmacy, and Pliny the Elder's "lens",[3] a glass globe filled with water, used to cauterize wounds. (Seneca wrote that it could be used to read letters "no matter how small or dim").[4][5] A convex lens used for forming a magnified image was described in the Book of Optics by Ibn al-Haytham in 1021.[6] After the book was translated during the Latin translations of the 12th century, Roger Bacon described the properties of a magnifying glass in 13th-century England. This was followed by the development of eyeglasses in 13th-century Italy.[6]

Magnification

US Navy 030903-N-2143T-001 Aviation Structural Mechanic Airman John Watkins uses a magnifying glass to check for defects
Magnifying glass on an arm lamp

The magnification of a magnifying glass depends upon where it is placed between the user's eye and the object being viewed, and the total distance between them. The magnifying power is equivalent to angular magnification (this should not be confused with optical power, which is a different quantity). The magnifying power is the ratio of the sizes of the images formed on the user's retina with and without the lens.[7] For the "without" case, it is typically assumed that the user would bring the object as close to one eye as possible without it becoming blurry. This point, known as the near point, varies with age. In a young child, it can be as close as 5 cm, while, in an elderly person it may be as far as one or two metres. Magnifiers are typically characterized using a "standard" value of 0.25 m.

The highest magnifying power is obtained by putting the lens very close to one eye and moving the eye and the lens together to obtain the best focus. The object will then typically also be close to the lens. The magnifying power obtained in this condition is MP0 = (0.25 m)Φ + 1, where Φ is the optical power in dioptres, and the factor of 0.25 m represents the assumed near point (¼ m from the eye). This value of the magnifying power is the one normally used to characterize magnifiers. It is typically denoted "m×", where m = MP0. This is sometimes called the total power of the magnifier (again, not to be confused with optical power).

However, magnifiers are not always used as described above because it is more comfortable to put the magnifier close to the object (one focal length away). The eye can then be a larger distance away, and a good image can be obtained very easily; the focus is not very sensitive to the eye's exact position. The magnifying power in this case is roughly MP = (0.25 m)Φ.

A typical magnifying glass might have a focal length of 25 cm, corresponding to an optical power of 4 dioptres. Such a magnifier would be sold as a "2×" magnifier. In actual use, an observer with "typical" eyes would obtain a magnifying power between 1 and 2, depending on where lens is held.

Alternatives

Loupe-triplet-30x-0a
A 30× Hastings triplet magnifier

Magnifying glasses typically have low magnifying power: 2×–6×, with the lower-power types being much more common. At higher magnifications, the image quality of a simple magnifying glass becomes poor due to optical aberrations, particularly spherical aberration. When more magnification or a better image is required, other types of hand magnifier are typically used. A Coddington magnifier provides higher magnification with improved image quality. Even better images can be obtained with a multiple-lens magnifier, such as a Hastings triplet. High power magnifiers are sometimes mounted in a cylindrical or conical holder with no handle. This is called a loupe.

Such magnifiers can reach up to about 30×, and at these magnifications the aperture of the magnifier becomes very small and it must be placed very close to both the object and the eye. For more convenient use or for magnification beyond about 30×, one must instead use a microscope.

Use as a symbol

The magnifying glass (i.e. Magnifying glass icon.svg, or U+1F50D in Unicode: 🔍) is commonly used as a symbolic representation for the ability to search or zoom, especially in computer software and websites.[8][9]

See also

References

  1. ^ Sines, George; Sakellarakis, Yannis A. (Apr 1987). "Lenses in Antiquity". American Journal of Archaeology. 91 (2): 191–6. doi:10.2307/505216.
  2. ^ Aristophanes, The Clouds, 765–70.
  3. ^ Pliny the Elder, Natural History, 36.67, 37.10.
  4. ^ Seneca, Natural Questions, 1.6.5–7.
  5. ^ The history of the telescope by Henry C. King, Harold Spencer Jones Publisher Courier Dover Publications, 2003 Pg 25 ISBN 0-486-43265-3, ISBN 978-0-486-43265-6
  6. ^ a b Kriss, Timothy C.; Kriss, Vesna Martich (April 1998). "History of the Operating Microscope: From Magnifying Glass to Micro neurosurgery". Neurosurgery. 42 (4): 899–907. doi:10.1097/00006123-199804000-00116. PMID 9574655.
  7. ^ Hecht, Eugene (1987). Optics (2nd ed.). Addison Wesley. pp. 186–188. ISBN 0-201-11609-X.
  8. ^ "Bing Search".
  9. ^ "Google Search".
A1689-zD1

A1689-zD1 is a galaxy in the Virgo constellation cluster. It was a candidate for the most distant and therefore earliest observed galaxy discovered as of February 2008, based on a photometric redshift.If the redshift, z~7.6, is correct, it would explain why the galaxy's faint light reaches us at infrared wavelengths. It could only be observed with Hubble Space Telescope's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) and the Spitzer Space Telescope's Infrared Array Camera exploiting the natural phenomenon of gravitational lensing: the galaxy cluster Abell 1689, which lies between Earth and A1689-zD1, at a distance of 2.2 billion light-years from us, functions as a natural "magnifying glass" for the light from the far more distant galaxy which lies directly behind it, at 700 million years after the Big Bang, as seen from Earth.

Chiffon (fabric)

Chiffon (French: [ʃi.fɔ̃]; English: , shif-ON (French chiffe cloth, or rag; Arabic شف šīff transparent, diaphanous, translucent fabric, or gauze; (عن 'an s.th.) to shimmer through, reveal) is a lightweight, balanced plain-woven sheer fabric, or gauze, woven of alternate S- and Z-twist crepe (high-twist) yarns. The twist in the crepe yarns puckers the fabric slightly in both directions after weaving, giving it some stretch and a slightly rough feel.

Early chiffon was made purely from silk. In 1938, however, a nylon version of chiffon was invented, and in 1958 polyester chiffon was invented and became immensely popular due to its resilience and low cost. Under a magnifying glass chiffon resembles a fine net or mesh which gives it some transparency.

Chiffon is most commonly used in evening wear, especially as an overlay, for giving an elegant and floating appearance to the gown. It is also a popular fabric used in blouses, ribbons, scarves and lingerie. Like other crêpe fabrics, chiffon can be difficult to work with because of its light and slippery texture. Due to this delicate nature, chiffon must be hand washed very gently.Since chiffon is a light-weight fabric that frays very easily, bound or French seams must be used to stop the fabric from fraying. Chiffon is smoother and more lustrous than the similar fabric georgette.

In African countries, such as Eritrea and Ethiopia, traditional ankle-length gowns are often made of chiffon which comes in many different designs and colors.In India, chiffon is a commonly used fabric for Sarees.

Coddington

Coddington could be

Coddington, Cheshire, United Kingdom

Coddington, Derbyshire, United Kingdom

Coddington, Herefordshire, United Kingdom

Coddington, Nottinghamshire, United Kingdom

Coddington, Wisconsin, United States

Coddington School, a historic school in Quincy, Massachusetts

Coddington magnifier, a single-lens magnifying glass

Coddington magnifier

A Coddington magnifier is a magnifying glass consisting of a single very thick lens with a central deep groove diaphragm at the equator, thus limiting the rays to those close to the axis, which again minimizes spherical aberration. This allows for greater magnification than a conventional magnifying glass, typically 10× up to 20×. Most single lens magnifiers are limited to 5× or so before significant distortion occurs. The drawback is that the diaphragm groove reduces the area seen through the magnifier.

Gemcutter

A gemcutter is a person who cuts, shapes, and polishes natural and synthetic gemstones. In historical use it usually refers to an artist who made hardstone carvings or engraved gems, a branch of miniature sculpture or ornament in gemstone.

Among a modern gemcutter's work are the following activities:

Positioning rough stone in a holder, and holding the stone against the edge of a revolving saw or lapidary slitter impregnated with diamond dust to cut and slit stone.

Removing cut stone and placing it in lapidary stick. A gemcutter then selects the shaping wheel and applies abrasive compound. They hold a lapidary stick against the revolving shaping wheel and lapidary disk to further shape stone and grind facets.

Examining stone for accuracy of cut, using a magnifying glass. A gemcutter polishes stone, using felt or canvas-covered polishing wheel, and polishing compounds, such as tripoli or jeweler's rouge.

Possibly using a mechanical facet-cutting device. A gemcutter may cut and polish diamonds for industrial purposes, and be designated as an Industrial-Diamond Polisher (jewelry-silver.).

Gyrodactylus salaris

Gyrodactylus salaris, commonly known as salmon fluke, is a tiny monogenean ectoparasite which lives on the body surface of freshwater fish. This leech-like parasite has been implicated in the reduction of Atlantic salmon populations in the Norwegian fjords. It also parasitises other species, including rainbow trout. G. salaris requires fresh water, but can survive in brackish water for up to 18 hours.The parasite is 0.5 mm (0.02 in) long, and cannot be seen with the naked eye, but it can be seen with a magnifying glass. On its posterior end is a haptor, a specialized organ for attaching to the host fish, which has sixteen hooks around its edge. The parasite is viviparous, that is, it produces live offspring.

The parasites give birth to live young nearly as big as themselves and at this time, a further generation is already growing inside the neonates.

Indigo Renderer

Indigo Renderer is a 3D rendering software that uses unbiased rendering technologies to create photo-realistic images. In doing so, Indigo uses equations that simulate the behaviour of light, with no approximations or guesses taken. By accurately simulating all the interactions of light, Indigo is capable of producing effects such as:

Depth of field, as when a camera is focused on one object and the background is blurred

Spectral effects, as when a beam of light goes through a prism and a rainbow of colours is produced

Refraction, as when light enters a pool of water and the objects in the pool seem to be “bent”

Reflections, from subtle reflections on a polished concrete floor to the pure reflection of a silvered mirror

Caustics, as in light that has been focused through a magnifying glass and has made a pattern of brightness on a surfaceIndigo uses methods such as Metropolis light transport (MLT), spectral light calculus, and virtual camera model. Scene data is stored in XML or IGS format.

Indigo features Monte-Carlo path tracing, bidirectional path tracing and MLT on top of bidirectional path tracing, distributed render capabilities, and progressive rendering (image gradually becomes less noisy as rendering progresses). Indigo also supports subsurface scattering and has its own image format (.igi).

Indigo was originally released as freeware until the 2.0 release, when it became a commercial product. The Indigo 3 series introduced many important features such as realtime editing capabilities, while version 4 of the software adds pure GPU rendering through a vendor neutral OpenCL path tracing engine.

Kine Exakta

The Kine Exakta was the first 35mm single-lens reflex (SLR) still camera in regular production. It was presented by Ihagee Kamerawerk Steenbergen GmbH, Dresden at the Leipziger Frühjahrsmesse in March 1936. The Exakta name was already used by Ihagee on a roll film SLR camera line since 1933, among these the Vest Pocket Exakta Model B from which the Kine Exakta inherited its general layout and appearance. The word Kine (cine, cinema, movie film) never appeared on the camera itself, only in the instruction manuals and advertising to distinguish it from the roll film variants. Several of its features constitute the foundation for the majority of 35mm SLR cameras produced ever since, although at this stage in an infant state.The perforated 35mm motion picture film had been used in miniature cameras for more than two decades using the 24x36mm negative format. The single lens reflex principle is even older and was widely used in cameras for the medium format plate- and film material. However, several obstacles had to be overcome to device a useful miniature SLR camera apart from the fact that the film material itself seriously restricted the usefulness of the negative: It is impossible to determine sharp focus on a ground glass for this format with the naked eye - even with a large aperture lens. To overcome this, Ihagee substituted the traditional ground glass focusing screen with a Plano-convex magnifying glass with the flat side facing downwards and ground to form a focusing screen visible magnified in the finder. To further improve focusing accuracy, a small magnifying glass could be swung into place for accurate focusing on a small part of the image. Also to improve focusing accuracy fast lenses were needed, and right from the start Carl Zeiss Jena provided the Tessar 1:2.8 f=5cm, soon to be followed by the Biotar 1:2 5cm and the Schneider-Kreuznach Xenar 1:2 f=5cm for the Kine Exakta.

Lens (optics)

A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis. Lenses are made from materials such as glass or plastic, and are ground and polished or molded to a desired shape. A lens can focus light to form an image, unlike a prism, which refracts light without focusing. Devices that similarly focus or disperse waves and radiation other than visible light are also called lenses, such as microwave lenses, electron lenses, acoustic lenses, or explosive lenses.

Magnification

Magnification is the process of enlarging the apparent size, not physical size, of something. This enlargement is quantified by a calculated number also called "magnification". When this number is less than one, it refers to a reduction in size, sometimes called minification or de-magnification.

Typically, magnification is related to scaling up visuals or images to be able to see more detail, increasing resolution, using microscope, printing techniques, or digital processing. In all cases, the magnification of the image does not change the perspective of the image.

Magnifier

A magnifier is a device used for magnification.

Magnifier can also refer to:

Magnifying glass, an optical device for magnification

Screen magnifier, software that magnifies part of a computer screen

Magnifier (Windows), a screen magnifier included with Microsoft Windows

Magnifying transmitter, alternate version of a Tesla Coil

Nimrud lens

The Nimrud lens, also called Layard lens, is a 3000-year-old piece of rock crystal, which was unearthed in 1850 by Austen Henry Layard at the Assyrian palace of Nimrud, in modern-day Iraq. It may have been used as a magnifying glass, or as a burning-glass to start fires by concentrating sunlight, or it may have been a piece of decorative inlay.

SAR-Lupe

SAR-Lupe is Germany's first reconnaissance satellite system and is used for military purposes. SAR is an abbreviation for synthetic aperture radar and "Lupe" is German for magnifying glass. The SAR-Lupe program consists of five identical (770 kg) satellites, developed by the German aeronautics company OHB-System which are controlled by a ground station which is responsible for controlling the system and analysing the retrieved data. A large data archive of images will be kept in a former Cold War bunker belonging to the Kommando Strategische Aufklärung (Strategic Reconnaissance Command) of the Bundeswehr.

Search box

A search box, search field or search bar is a graphical control element used in computer programs, such as file managers or web browsers, and on web sites. A search box is usually a single-line text box or search icon ( which will transform into a search box on click activity) with the dedicated function of accepting user input to be searched for in a database. Search boxes on web pages are usually used to allow users to enter a query to be submitted to a Web search engine server-side script, where an index database is queried for entries that contain one or more of the user's keyword research.

Search boxes are commonly accompanied by a search button (sometimes indicated only by a magnifying glass symbol) to submit the search. However, the search button may be omitted as the user may press the enter key to submit the search, or the search may be sent automatically to present the user with real-time results.

Sensory garden

A sensory garden is a self-contained garden area that allows visitors to enjoy a wide variety of sensory experiences. Sensory gardens are designed to provide opportunities to stimulate the senses, both individually and in combination, in ways that users may not usually encounter.Sensory gardens have a wide range of educational and recreational applications. They can be used in the education of special-needs students, including people with autism. As a form of horticultural therapy, they may be helpful in the care of people with dementia.Sensory gardens can be designed in such a way as to be accessible and enjoyable for both disabled and non-disabled users. A sensory garden, for example, may contain features accessible to the disabled individual such as: scented and edible plants, sculptures and sculpted handrails, water features designed to make sound and play over the hands, textured touch-pads, magnifying-glass screens, braille and audio induction loop descriptions. Depending on the user group, other provisions may integrate sound and music more centrally to combine the play needs of younger users with their sensory needs.

Many sensory gardens devote themselves to providing experience for multiple senses; those specialising in scent are sometimes called scented gardens, those specialising in music/sound are sound gardens where the equipment doubles up to provides an enhanced opportunity for strategic developmental, learning and educational outcomes.

Sensory Gardens usually have an enhanced infrastructure to permit wheelchair access and meet other accessibility concerns; the design and layout provides a stimulating journey through the senses, heightening awareness, and bringing positive learning experiences.

Some sensory gardens

Simple lens

In optics, a simple lens or singlet lens is a lens consisting of a single simple element. Typical examples include a magnifying glass or a lens in a pair of simple reading glasses.Simple lenses are prone to aberrations, especially chromatic aberration. They cannot be used for precise imaging and make poor camera lenses. They are commonly used for laser applications, however, where the beams are both monochromatic (minimizing chromatic aberration) and narrow (minimizing spherical aberration).

Some cameras with fixed lenses have been made using a simple lens, usually a meniscus lens with the convex face facing outward. In such examples the lens aperture is made small and in some cases (such as the Kodak Brownie 127 camera), the film plane is curved to reduce the impact of aberrations.

Video magnifier

This article is about tools for visually-impaired people. For image-processing techniques not related to the visually impaired, please create other articles such as Eulerian video magnification.

Video magnifiers are electronic devices that use a camera and a display screen to perform digital magnification of printed materials. The display screen is usually LCD or a similar flat-screen technology (although older video magnifiers have used CRT displays), and the device usually includes a lamp to illuminate the source material. Video magnifiers are designed to be mostly used by people with low vision that cannot be helped using a conventional magnifying glass.

Virtual Magnifying Glass

Virtual Magnifying Glass is an open-source, screen magnification tool for Microsoft Windows and Linux.

Virtual Magnifying Glass is designed for the visually impaired and others who need to magnify part of the computer display. Unlike most similar programs, it does not open a separate program window for the magnification but instead puts a movable magnifying glass on the screen.

Virtual Magnifying Glass works on a variety of platforms (Windows, Linux, FreeBSD, Mac OS) due to being developed with the Free Pascal compiler. There is no charge for the software.

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