Friday, March 16, 2012

The Aspheric Lens

To avoid the spherical aberration of simple lenses one can use an aspheric lens in which the curvature varies as a function of the radial distance. It can have a positive curvature near the center of the lens and negative curvature near the edges to lengthen the focal length so that the rays all come together at the same point. Another method used with telescopes is the corrector plate.

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