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Photochromic Lens
A photochromic lens is an optical lens that darkens on exposure to light of sufficiently high frequency, most commonly ultraviolet (UV) radiation. In the absence of activating light, the lenses return to their clear state. Photochromic lenses may be made of polycarbonate, or another plastic. Glass lenses use visible light to darken. They are principally used in glasses that are dark in bright sunlight, but clear, or more rarely, lightly tinted in low ambient light conditions. They darken significantly within about a minute of exposure to bright light and take somewhat longer to clear. A range of clear and dark transmittances is available. Two kinds of photochromic lenses were popularized, the first being glass containing silver halides. These silver-based lenses became largely obsolete with the introduction of photochromic organic compounds. The other type are plastic, usually polycarbonate combined with photochromic organic compounds. These processes are reversible; once the len ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University College London
University College London (Trade name, branded as UCL) is a Public university, public research university in London, England. It is a Member institutions of the University of London, member institution of the Federal university, federal University of London, and is the second-largest list of universities in the United Kingdom by enrolment, university in the United Kingdom by total enrolment and the largest by postgraduate enrolment. Established in 1826 as London University (though without university degree-awarding powers) by founders who were inspired by the radical ideas of Jeremy Bentham, UCL was the first university institution to be established in London, and the first in England to be entirely secular and to admit students regardless of their religion. It was also, in 1878, among the first university colleges to admit women alongside men, two years after University College, Bristol, had done so. Intended by its founders to be Third-oldest university in England debate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glass Compositions
Glass is an amorphous (non-crystalline solid, non-crystalline) solid. Because it is often transparency and translucency, transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window panes, tableware, and optics. Some common objects made of glass are named after the material, e.g., a Tumbler (glass), "glass" for drinking, "glasses" for vision correction, and a "magnifying glass". Glass is most often formed by rapid cooling (quenching) of the Melting, molten form. Some glasses such as volcanic glass are naturally occurring, and obsidian has been used to make arrowheads and knives since the Stone Age. Archaeological evidence suggests glassmaking dates back to at least 3600 BC in Mesopotamia, Ancient Egypt, Egypt, or Syria. The earliest known glass objects were beads, perhaps created accidentally during metalworking or the production of faience, which is a form of pottery using lead glazes. Due to its ease of formability int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromism
In chemistry, chromism is a process that induces a change, often reversible, in the colors of compounds. In most cases, chromism is based on a change in the electron states of molecules, especially the π- or d-electron state, so this phenomenon is induced by various external stimuli which can alter the electron density of substances. It is known that there are many natural compounds that have chromism, and many artificial compounds with specific chromism have been synthesized to date. It is usually synonymous with chromotropism, the (reversible) change in color of a substance due to the physical and chemical properties of its ambient surrounding medium, such as temperature and pressure, light, solvent, and presence of ions and electrons. Chromism is classified by what kind of stimuli are used. Examples of the major kinds of chromism are as follows. * thermochromism is chromism that is induced by heat, that is, a change of temperature. This is the most common chromism of all. * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corrective Lenses
A corrective lens is a transmissive optical device that is worn on the eye to improve visual perception. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia. Glasses or "spectacles" are worn on the face a short distance in front of the eye. Contact lenses are worn directly on the surface of the eye. Intraocular lenses are surgically implanted most commonly after cataract removal but can be used for purely refractive purposes. Prescription of corrective lenses Corrective lenses are typically prescribed by an ophthalmologist or an optometrist. The prescription consists of all the specifications necessary to make the lens. Prescriptions typically include the power specifications of each lens (for each eye). Strengths are generally prescribed in quarter- diopter steps (0.25 D), because most people cannot generally distinguish between smaller increments (e.g., eighth-diopter steps / 0.125 D). The use of improper corr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Essilor
Essilor International is a French multinational corporation specialized in the design, manufacture and sale of ophthalmic lenses, optical equipment and instruments. It is the world's largest manufacturer of ophthalmic lenses. Founded in 1972 out of the merger of two French companies operating in the sector, ''Essel'' and ''Silor'', it is headquartered in Charenton-le-Pont, near Paris. Since October 2018, it is a subsidiary of EssilorLuxottica which arose out of a merger between Essilor and the Italian eyewear corporation Luxottica. In January 2017, Essilor announced a merger with Luxottica, in which Essilor would acquire the latter while Luxottica executive chairman Leonardo Del Vecchio would become co-executive chairman of the newly formed holding company, EssilorLuxottica. On 1 October 2018, the new entity was born, resulting in a combined market capitalization of approximately €57 billion. History 1849–1972: Essel and Silor ''Essel'' (Société des Lunetteries ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photosensitive Glass
Photosensitive glass, also called photostructurable glass (PSG) or photomachinable glass, is a glass in the lithium-silicate family of glasses onto which images can be etched using shortwave radiations, such as ultraviolet. Photosensitive glass was first discovered by S. Donald Stookey in 1937.Paul, p. 333Encyclopædia Britannica, pp. 194–209Maluf, pp. 62–63 Exposure process When the glass is exposed to UV light with wavelengths between 280 and 320 nm, a latent image is formed. The glass remains transparent at this stage, but its ability to absorb UV light increases. This increased absorption is only detectable using UV transmission spectroscopy and is caused by an oxidation–reduction reaction that occurs inside the glass during exposure. This reaction causes cerium ions to oxidize to a more stable state, and silver ions are reduced to silver. Post-exposure heat treatment The latent image captured in the glass is made visible by heating. This heat treatment is done ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Persol
Persol is an Italian luxury eyewear brand specializing in the manufacturing of sunglasses and optical frames. It is one of the oldest eyewear companies in the world and is owned by the Luxottica group. The name is derived from the Italian ''per il sole'', meaning "for the sun". Formed in 1917 by Giuseppe Ratti, Persol originally catered to pilots and sports drivers. Currently, the company markets durable sports sunglasses. The company trademark is a silver arrow. History In 1917 Giuseppe Ratti, owner of Berry optical, started producing his first glasses and lenses for athletes and aviators. The company developed a flexible stem, known as the patented Meflecto system, which was one of the first spring hinges for eyewear. Persol was introduced to the United States in 1962 and opened its first boutique on Rodeo Drive in Beverly Hills in 1991. Technology Currently all plastic Persol spectacles are made in Italy using cellulose acetate In biochemistry, cellulose acetate refer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Serengeti (sunglasses Brand)
Serengeti Eyewear is a sunglasses line owned by Bollé Brands. Their main focus is eye protection; the company researches and develops technology such as photochromic lenses, polarized lenses, spectral control, among others. History The brand was developed by Corning Incorporated. In 1984, Corning considered closing Serengeti due to poor financial performance. However, entrepreneur Zaki Mustafa convinced the board that he could save the brand. He attributed poor sales to a product-centric focus, poor marketing, anemic customer service, and inefficient asset management. With only fifty-two employees, he successfully increased sales from $5 million in 1985 to $62 million in 1992. Technology and design Serengeti sunglasses include tinted photochromic and polarized lenses. Tucker Viemeister designed aviator style sunglasses in sepia tones for Serengeti in the 1980s. Acquisition The Serengeti brand was acquired by Bushnell Corporation in September 2000. Bollé, Cébé and Seren ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carl Zeiss AG
Zeiss ( ; ) is a German manufacturer of optical systems and optoelectronics, founded in Jena, Germany, in 1846 by optician Carl Zeiss. Together with Ernst Abbe (joined 1866) and Otto Schott (joined 1884) he laid the foundation for today's multinational company. The current company emerged from a reunification of Carl Zeiss companies in East and West Germany with a consolidation phase in the 1990s. ZEISS is active in four business segments with approximately equal revenue (Industrial Quality and Research, Medical Technology, Consumer Markets and Semiconductor Manufacturing Technology) in almost 50 countries, has 30 production sites and around 25 development sites worldwide. Carl Zeiss AG is the holding of all subsidiaries within Zeiss Group, of which Carl Zeiss Meditec AG is the only one that is traded at the stock market. Carl Zeiss AG is owned by the foundation Carl-Zeiss-Stiftung. The Zeiss Group has its headquarters in southern Germany, in the small town of Oberkochen, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sunglass
Sunglasses or sun glasses (informally called shades or sunnies; more names below) are a form of protective eyewear designed primarily to prevent bright sunlight and high-energy visible light from damaging or discomforting the eyes. They can sometimes also function as a visual aid, as variously termed spectacles or glasses exist, featuring lenses that are colored, polarized or darkened. In the early 20th century, they were also known as sun cheaters (cheaters then being an American slang term for glasses). Since the 1930s, sunglasses have been a popular fashion accessory, especially on the beach. The American Optometric Association recommends wearing sunglasses that block ultraviolet radiation (UV) whenever a person is in the sunlight to protect the eyes from UV and blue light, which can cause several serious eye problems. Their usage is mandatory immediately after some surgical procedures, such as LASIK, and recommended for a certain time period in dusty areas, when leavin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
