Physics

What is Abbe number?

The Abbe number also called the V-number or con-stringency of a transparent material in optics and lens design, is a rough estimate of scattering of the material (change in the index of refraction function of wavelength), with high V values suggesting minimal dispersion. German physicist Ernst Abbe (1840–1905) develop the Abbe number. The normal frequency in fibers should do not confuse with the word V-number.

Abbe numbers use to categorize the chromatically of glass and other optical materials. Higher dispersion flint glasses, for example, have V 55, whereas lower dispersion crown glasses have higher Abbe numbers. V value varies from less than 25 for very thick flint glasses to roughly 34 for poly-carbonates, 65 for typical crown glasses, and 75 to 85 for some fluorite and phosphate head glasses.

The ratio of Abbe numbers is proportional to dispersal (slope of refractive index vs wavelength) in the wavelength range. Where the human eye is most responsive, which implement in the construction of achromatic lenses.

The Abbe number of materials plot against its refractive index to generate an Abbe diagram, call “glass veil”. This can be a six-digit glass code or an alphabet code, as in the Schott Glass catalog.

The need for refractive powers of the elements of achromatic lenses calculates using the Abbe numbers of glasses. Their mean refractive indices in order to cancel chromatic aberration to the first order. It’s worth noting that the two components that go into the achromatic doublet design formulae are identical.

Alternative definitions of the Abbe number are mostly adopted due to the difficulty and complexity of manufacturing sodium and hydrogen lines (ISO 7944). Rather than the traditional definition, above, using the refractive index fluctuation between the F and C hydrogen lines. The alternate measure utilizing the subscript “e”