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Online services
Any business that provides its subscribers with a wide variety of data transmitted over telecommunications lines, an infrastructure in which they can communicate with one another as well as the means to connect with an almost unlimited number of third-party information providers.
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Astigmatic power lens
Eyewear; Optometry
Lens bringing a paraxial pencil of parallel light to two separate line foci mutually at right angles and hence having vertex power in only the two principal meridians.
Astronomical telescope
Eyewear; Optometry
Compound optical system, afocal in normal adjustment, consisting of a positive objective element or group and a positive ocular element or group forming a magnified, inverted ...
Condensing lens
Eyewear; Optometry
A convex lens used to condense the illuminating beam into the patient's eye and to form a real inverted image of the retina thus illuminated.
Concave lens
Eyewear; Optometry
Lens which causes parallel incident light to diverge from a virtual focus. Also known as minus-power lens.
Abbe number
Eyewear; Optometry
Mathematical expression for determining the correction for chromatic aberration of an optical material of component.
Astigmatic difference
Eyewear; Optometry
Vertex power in the second principal meridian minus that in the first principal meridian.
Optical drive
Multimedia;
An optical drive is an electronic device used to seek, read, and write data on an optical disc. An optical drive may reside in an optical library or as a stand-alone unit.
