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lens
lens
lens A transparent biconvex structure in the eyes or analogous organs of many animals, responsible for directing light onto light-sensitive cells. In vertebrates it is a flexible structure centred behind the iris and attached by
suspensory ligaments to the
ciliary body. In terrestrial species its main function is to focus images onto the retina. To focus on near objects, the circular muscles in the ciliary body contract and the lens becomes more convex; contraction of the radial muscles in the ciliary body flattens the lens for focusing on distant objects (see also
accommodation).
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Lens stem cells may reside outside the lens capsule: an hypothesis.(Commentary)(Clinical report)
Magazine article from: Theoretical Biology and Medical Modelling; 6/8/2007; ; 700+ words
; ...corresponding author) [1]; Rita A Meyer [2] Background Lens background The vertebrate lens is a transparent cellular structure, specialized to focus and transmit light. The lens is composed of two cell types - epithelial cells...
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Lens accessories: stress your visual limits.(lens accessories for camcorders)(includes directory of manufacturers)
Magazine article from: Videomaker; 2/1/1998; ; 700+ words
; ...easier ways to modify your lens is through the use of closeup (or diopter) lenses. Simply add one or two to the front of your lens to enable it to focus...length is a +2 diopter lens (1/0.5). When you combine two or more diopter lenses, calculate the combined...
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LENSES INTO FOCUS -- How lenses work and how to choose them.(Statistical Data Included)
Magazine article from: Digital Video Magazine; 4/1/2002; ; 700+ words
; ...the more wide angle the lens. All prime lenses have a fixed focal length...operators to consider prime lenses. With a zoom lens, users can increase and...the more expensive the lens. Adapters and extenders Lenses for all types of cameras...
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Lenses for Every Eye.
Magazine article from: U.S. News & World Report; 3/5/2007; ; 700+ words
; ...silicone hydrogel lenses, an improved version of the soft lens introduced in 1971...permeable rigid lenses. That's important...you're getting a lens that breathes better...Association's contact lens and cornea section...silicone hydrogel lenses increased 50 percent...
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Telecentric lenses simplify noncontact metrology.
Magazine article from: Test & Measurement World; 10/15/2001; ; 700+ words
; ...you can't use these lenses in all applications. Lens manufacturers can make...conventional machine-vision lens. All imaging lenses have an aperture stop...the lens, or a group of lenses. In a conventional lens, the opening or closing...
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Camera lenses.
Magazine article from: PSA Journal; 1/1/1991; ; 700+ words
; ...needed in a fine lens. f) In reality, most of today's lenses are capable of producing...above. Normal Lens Before taking up...and "accessory lenses," let's define...point behind the lens so clearance is achieved.) These normal lenses have a focal length...
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Aspheric lenses in practice.(dispensing)
Magazine article from: Optician; 7/12/2002; ; 700+ words
; ...catalogues. Since some lens ranges change more...that all of these lenses are still, necessarily...introduced to try to give lens designers more control...states that these lenses are optically indistinguishable...also clear from the lens equations that they...equivalent conic ...
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Lens hoods.
Magazine article from: PSA Journal; 8/1/1995; ; 700+ words
; ...precision cameras and lenses advise the use of a lens hood. This is sufficient...sizes for different lenses. Also, besides...hood protects the lens from rain and fingerprints...no wider than the lens mount are essential...manufacturers of such lenses include a threaded...
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Contact Lenses-a New Way to See
Newspaper article from: The Washington Post; 5/22/1990; ; 700+ words
; ...forced under the lens. Even so, it...people who wear hard lenses to take them out...careful. For contact lens wearers, that means...and care for the lenses. Lenses must be...on them. Contact lens wearers can't take...taking care of their lenses. Wearing dirty lenses...
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LENS MAKER TAKES SHARPER FOCUS ON DIFFUSE PRODUCTION PROCESS
Newspaper article from: Roanoke Times & World News; 5/15/2004; ; 700+ words
; ...many manufacturers of eyeglass lenses. John Hogan, president of The Spectacle Lens Group, said this week that...professional affairs for The Spectacle Lens Group, said a set of Definity lenses made from a basic plastic lens blank probably retails from...
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Lens
Encyclopedia entry from: The Gale Encyclopedia of Science
...surface of a lentil bean. Lenses (the plural of lens) are important in everyday...one focal length behind the lens.) Lenses are important because they...combinations of spherical lenses or by using a lens with a different profile...
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lens
Book article from: The Columbia Encyclopedia, Sixth Edition
...known as a crystalline lens. Classification of Lenses All rays of light...and Production of Lenses Generally each curved surface of a lens is made as a portion...focal length of the lens. It varies with different lenses, according to the...
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Contact Lens
Book article from: Medical Discoveries
...types of contact lenses. One is the corneal contact lens which covers only...plastic contact lens were introduced...Kalt's contact lenses. In 1889 Muller...possible to wear these lenses very long. Joseph...pass between the lens and the cornea...
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Eyeglass Lens
Book article from: How Products Are Made
Eyeglass Lens Background Eyeglass lenses are glass or plastic optical...virtually replaced by glass lenses. The convex lens was the first optical lens...but other corrective lenses followed, including the concave lens for the correction of near...
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Camera Lens
Book article from: How Products Are Made
...replacing a simple lens with a group of lenses called lens elements, which are lenses of different shapes and distances of separation...disposable cameras are equipped with panoramic lenses. A fish-eye lens is also a special kind of wide-angle lens...
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