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Haidinger's Brush
Haidinger's brush, more commonly known as Haidinger's brushes is an image produced by the eye, an entoptic phenomenon, first described by Austrian physicist Wilhelm Karl von Haidinger in 1844. Haidinger saw it when he looked through various minerals that polarized light. Many people are able to perceive polarization of light. Haidinger's brushes may be seen as a yellowish horizontal bar or bow-tie shape (with "fuzzy" ends, hence the name "brush") visible in the center of the visual field against the blue sky viewed while facing away from the sun, or on any bright background. It typically occupies roughly 3–5 degrees of vision, about twice or three times the width of one's thumb held at arm's length. The direction of light polarization is perpendicular to the yellow bar (i.e., vertical if the bar is horizontal). Fainter bluish or purplish areas may be visible between the yellow brushes (see illustration). Haidinger's brush may also be seen by looking at a white area on many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haidinger's Brush
Haidinger's brush, more commonly known as Haidinger's brushes is an image produced by the eye, an entoptic phenomenon, first described by Austrian physicist Wilhelm Karl von Haidinger in 1844. Haidinger saw it when he looked through various minerals that polarized light. Many people are able to perceive polarization of light. Haidinger's brushes may be seen as a yellowish horizontal bar or bow-tie shape (with "fuzzy" ends, hence the name "brush") visible in the center of the visual field against the blue sky viewed while facing away from the sun, or on any bright background. It typically occupies roughly 3–5 degrees of vision, about twice or three times the width of one's thumb held at arm's length. The direction of light polarization is perpendicular to the yellow bar (i.e., vertical if the bar is horizontal). Fainter bluish or purplish areas may be visible between the yellow brushes (see illustration). Haidinger's brush may also be seen by looking at a white area on many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cathode Ray Tube
A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms ( oscilloscope), pictures (television set, computer monitor), radar targets, or other phenomena. A CRT on a television set is commonly called a picture tube. CRTs have also been used as memory devices, in which case the screen is not intended to be visible to an observer. The term ''cathode ray'' was used to describe electron beams when they were first discovered, before it was understood that what was emitted from the cathode was a beam of electrons. In CRT television sets and computer monitors, the entire front area of the tube is scanned repeatedly and systematically in a fixed pattern called a raster. In color devices, an image is produced by controlling the intensity of each of three electron beams, one for each additive primary color (red, green, and bl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Shurcliff
William Asahel Shurcliff (March 27, 1909 – June 20, 2006) was an American physicist. Biography He received his BA cum laude in 1930, a PhD in Physics in 1934, and a degree in Business Administration in 1935, all from Harvard University. In the 1930s he worked at the Spectrophotometric Laboratory at the Calco Chemical Division of the American Cyanamid Company. Atomic bomb In 1942 he joined the staff of the Office of Scientific Research and Development, where he worked in the Liaison Office, processing technical information obtained from overseas and routing it to divisions within US government research where it could be useful. In May 1942 he was chosen by his boss, Vannevar Bush, to be part of S-1 Section, which would become the Manhattan Project to make the atomic bomb. Shurcliff's role was specifically to be a censor of patents: he would review patent applications from the private sector which appeared to impinge on topics being developed in secret by the government, and put t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bibliothèque Nationale De France
The Bibliothèque nationale de France (, 'National Library of France'; BnF) is the national library of France, located in Paris on two main sites known respectively as ''Richelieu'' and ''François-Mitterrand''. It is the national repository of all that is published in France. Some of its extensive collections, including books and manuscripts but also precious objects and artworks, are on display at the BnF Museum (formerly known as the ) on the Richelieu site. The National Library of France is a public establishment under the supervision of the Ministry of Culture. Its mission is to constitute collections, especially the copies of works published in France that must, by law, be deposited there, conserve them, and make them available to the public. It produces a reference catalogue, cooperates with other national and international establishments, and participates in research programs. History The National Library of France traces its origin to the royal library founded at t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prisoner's Cinema
Prisoner's cinema is the phenomenon of a "light show" of various colors that appear out of the darkness. The light has a form, but those that have seen it find it difficult to describe. Sometimes, the cinema lights resolve into human or other figures. The phenomenon is reported by prisoners confined to dark cells and by others kept in darkness, voluntarily or not, for long periods of time. It has also been reported by truck drivers, pilots, and practitioners of intense meditation. Astronauts and other individuals who have been exposed to certain types of radiation have reported witnessing similar phenomena. Scientists believe that the cinema is a result of phosphenes combined with the psychological effects of prolonged lack of exposure to light, and others have noted a connection between the form the lights take and neolithic cave paintings. Popular culture The pilot episode for the original ''Twilight Zone'' series, "Where Is Everybody?," depicts elaborate, fully realistic hallu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isolation Tank
An isolation tank, sensory deprivation tank, float tank, float pod, float cabin, flotation tank, or sensory attenuation tank is a water filled, pitch-black, light-proof, soundproof environment heated to the same temperature as the skin, developed in 1954 by John C. Lilly. Flotation tanks are widely advertised as a form of alternative medicine but beneficial health effects are unproven. Method The tank is filled with 10 inches of water which contains enough dissolved Epsom salt to create a specific gravity of approximately 1.25–1.26. This environment allows an individual to float effortlessly on the surface of the water. History The isolation tank was developed in 1954 by John C. Lilly, a medical practitioner and neuropsychiatrist. During his training in psychoanalysis at the US National Institute of Mental Health (NIMH), Lilly experimented with sensory deprivation. Widespread commercial interest and use of the isolation tank did not occur until 1972, when Glenn Perry, a com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haidinger Fringe
Haidinger fringes are interference fringes formed by the interference of monochromatic and coherent light to form visible dark and bright fringes. Fringe localization is the region of space where fringes with reasonably good contrast are observed. Haidinger fringes are fringes localized at infinity. Also known as fringes of equal inclination, these fringes result when light from an extended source falls on a thin film made of an optically denser medium. These fringes indicate the positions where light interferes, emerging from the medium at an equal angle. Hecht They are also observed in Fabry-Pérot and Michelson interferometers. They can be observed by introducing a converging lens between the film and observation plane with focus of the lens lying in observation plane. See also *Wilhelm Karl Ritter von Haidinger *Haidinger's brush Haidinger's brush, more commonly known as Haidinger's brushes is an image produced by the eye, an entoptic phenomenon, first described by Austr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Floater
Floaters or eye floaters are sometimes visible deposits (e.g., the shadows of tiny structures of protein or other cell debris projected onto the retina) within the eye's vitreous humour ("the vitreous"), which is normally transparent, or between the vitreous and retina.Cline D; Hofstetter HW; Griffin JR. ''Dictionary of Visual Science''. 4th ed. Butterworth-Heinemann, Boston 1997. They can become particularly noticeable when looking at a blank surface or an open monochromatic space, such as blue sky. Each floater can be measured by its size, shape, consistency, refractive index, and motility. They are also called ''muscae volitantes'' (Latin for 'flying flies'), or ''mouches volantes'' (from the same phrase in French). The vitreous usually starts out transparent, but imperfections may gradually develop as one ages. The common type of floater, present in most people's eyes, is due to these degenerative changes of the vitreous. The perception of floaters, which may be annoying ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amblyopia
Amblyopia, also called lazy eye, is a disorder of sight in which the brain fails to fully process input from one eye and over time favors the other eye. It results in decreased vision in an eye that typically appears normal in other aspects. Amblyopia is the most common cause of decreased vision in a single eye among children and younger adults. The cause of amblyopia can be any condition that interferes with focusing during early childhood. This can occur from poor alignment of the eyes (strabismic), an eye being irregularly shaped such that focusing is difficult, one eye being more nearsighted or farsighted than the other (refractive), or clouding of the lens of an eye (deprivational). After the underlying cause is addressed, vision is not restored right away, as the mechanism also involves the brain. Amblyopia can be difficult to detect, so vision testing is recommended for all children around the ages of four to five. Early detection improves treatment success. Glasse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinal Birefringence Scanning
Retinal birefringence scanning (RBS) is a method for detection the central fixation of the eye. The method can be used in pediatric ophthalmology for screening purposes. By simultaneously measuring the central fixation of both eyes, small- and large-angle strabismus can be detected. The method is not invasive and requires little cooperation by the patient, so it can be used for detecting strabismus in young children. The method provides a reliable detection of strabismus and has also been used for detecting certain kinds of amblyopia. RBS uses the human eye's birefringent properties to identify the position of the fovea and the direction of gaze, and thereby to measure any binocular misalignment. __TOC__ Principle Birefringent material has a refractive index that depends on the polarization state and propagation direction of light. The main contribution to the birefringence of the eye stems from the Henle fibers. These fibers (named after Friedrich Gustav Jakob Henle) are photore ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Birefringence
Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are said to be birefringent (or birefractive). The birefringence is often quantified as the maximum difference between refractive indices exhibited by the material. Crystals with non-cubic crystal structures are often birefringent, as are plastics under mechanical stress. Birefringence is responsible for the phenomenon of double refraction whereby a ray of light, when incident upon a birefringent material, is split by polarization into two rays taking slightly different paths. This effect was first described by Danish scientist Rasmus Bartholin in 1669, who observed it in calcite, a crystal having one of the strongest birefringences. In the 19th century Augustin-Jean Fresnel described the phenomenon in terms of polarization, understanding light as a wave with field components in transverse polariz ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
