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lens
lens
lens A transparent optical element, either glass, crystalline, or plastic, that refracts light to form an image. A lens has either concave or convex surfaces, so that parallel light which strikes it is refracted either towards the
focal point, as in a
converging lens, or away from it, as in a
diverging lens. A lens which is thin compared with its diameter will have a more distant focal point (i.e. a longer
focal length) than a thicker one, will be easier to manufacture, and will suffer less from
chromatic aberration and
spherical aberration. In practice, to reduce these and other
distortions, combinations of lenses, known as
compound lenses, are used. See also
achromatic lens.
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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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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 colour vision deficiency and reading difficulties in optometric practice.(COLOURED LENSES)
Magazine article from: Optometry Today; 4/10/2009; ; 700+ words
; ...a rigid (hard) lens material. A little...introduction of these lenses, the present author...if these coloured lenses were to be incorporated as a spectacle lens correction, a marked...front surface of each lens would produce more...acceptable spectacle lenses, where both would...
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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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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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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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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 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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Lens solution makers need to account for 'human factors'.
Newspaper article from: Medical Device Daily; 6/12/2008; 700+ words
; ...state that makers of contact lens solutions should come up...proof way to ensure that lenses are sterile, the subtext...the efficacy of contact lens solutions on lenses is complicated by the wide range of lens types on the market...
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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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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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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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