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What is a Fresnel Lens?

Fresnel Lens: A Fresnel lens is a type of lens invented by French physicist Augustin-Jean Fresnel. Originally developed for lighthouses, the design enables the construction of lenses of large aperture and short focal length without the weight and volume of material which would be required in conventional lens design. The conventional magnifying glass lens is thick in the middle and thin at the ....

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What is an Aspheric Lens?

       Aspheric Lens: An aspheric lens is designed for aberration correction. With the help of aspheric lens, the image formed is distortion free. An aspheric lens is a lens whose surfaces profile neither a portion of a sphere nor of a circular cylinder. Since it is not spherical, the conventional processes no longer apply to making aspheric surfaces. This is why asp....

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History of Optics

     Ancients used mirrors of polished copper, bronze, and speculum.     Chinese ....

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History of Microscope

  The first compound microscopes produced by Zacharias Janssen (Dutch,1580-1638)in 1595 , was simply a tube with lenses at each end. The magnification of these early scopes ranged from 3X to 9X, depending on the size of the diaphragm ....

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History of Telescope

    In 1608, a Dutch eyeglass maker named Hans Lippershey looked at a church steeple through two lenses placed one in front of the other and saw that the image was magnified. Unfortunately the telescopes built on Lippershey's model had poor image quality, caused by the b....

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