Dielectric lens | Wikipedia audio article

Описание: This is an audio version of the Wikipedia Article:
https://en.wikipedia.org/wiki/Lunebur...


00:01:16 1 Designs
00:01:25 1.1 Luneburg's solution
00:02:56 1.2 Maxwell's fish-eye lens
00:04:04 1.2.1 Publication and attribution
00:04:53 2 Applications
00:05:34 2.1 Radar reflector
00:06:13 2.2 Microwave antenna
00:08:26 3 Path of a ray within the lens
00:15:40 4 See also



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SUMMARY
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A Luneburg lens (originally Lüneburg lens, often incorrectly spelled Luneberg lens) is a spherically symmetric gradient-index lens. A typical Luneburg lens's refractive index n decreases radially from the center to the outer surface. They can be made for use with electromagnetic radiation from visible light to radio waves.
For certain index profiles, the lens will form perfect geometrical images of two given concentric spheres onto each other. There are an infinite number of refractive-index profiles that can produce this effect. The simplest such solution was proposed by Rudolf Luneburg in 1944. Luneburg's solution for the refractive index creates two conjugate foci outside of the lens. The solution takes a simple and explicit form if one focal point lies at infinity, and the other on the opposite surface of the lens. J. Brown and A. S. Gutman subsequently proposed solutions which generate one internal focal point and one external focal point. These solutions are not unique; the set of solutions are defined by a set of definite integrals which must be evaluated numerically.