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Abbe number. In optics and lens design, the Abbe number, also known as the V-number or constringence of a transparent material, is an approximate measure of the material's dispersion (change of refractive index versus wavelength), with high values of V indicating low dispersion. It is named after Ernst Abbe (1840–1905), the German physicist ...
The ratio of this measured beam parameter product to that of the ideal is defined as M 2, so that M 2 =1 describes an ideal beam. The M 2 value of a beam is conserved when it is transformed by diffraction-limited optics. The outputs of many low and moderately powered lasers have M 2 values of 1.2 or less, and are essentially diffraction-limited.
In optics, the Abbe sine condition is a condition that must be fulfilled by a lens or other optical system in order for it to produce sharp images of off-axis as well as on-axis objects. It was formulated by Ernst Abbe in the context of microscopes. [ 1] The Abbe sine condition says that. the sine of the object-space angle should be ...
In the Abbe refractometer the liquid sample is sandwiched into a thin layer between an illuminating prism and a refracting prism. The refracting prism is made of a glass with a high refractive index (e.g., 1.75) and the refractometer is designed to be used with samples having a refractive index smaller than that of the refracting prism.
Abbe condensers are difficult to use for magnifications of above 400X, as the aplanatic cone is only representative of a numerical aperture (NA) of 0.6. This condenser is composed of two lenses, a plano-convex lens somewhat larger than a hemisphere and a large bi-convex lens serving as a collecting lens to the first.
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Higher Abbe numbers mean a better lens material, and lower Abbe numbers result in the presence of chromatic aberration (i.e., color fringes above/below or to the left/right of a high contrast object), especially in larger lens sizes and stronger prescriptions (beyond ±4.00D). Generally, lower Abbe numbers are a property of mid and higher index ...
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