constringence

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constringence 

A positive number (symbol: V) which specifies any transparent medium. It is equal to
V = nd − 1/nFnC
where nD, nF and nC are the refractive indices for the Fraunhofer spectral lines d (587.6 nm), F (486.1 nm) and C (656.3 nm). A material with a high constringence (e.g. V = 50) produces less chromatic aberration than one with a low constringence (e.g. V = 30). The reciprocal of the constringence is called the dispersive power. Syn. Abbé's number; V-value. See dispersion; crown glass; flint glass; Fraunhofer's lines.
Table C8 Constringence (V) of some transparent media (index of refraction n)
nV
glass
spectacle crown1.52359
dense barium crown1.62060
lanthana crown1.71354
zinc crown1.50861
light flint1.58141
dense flint1.62036
extra dense flint1.70630
titanium oxide1.70131
polymer
PMMA1.49257
CR-391.49859
Polycarbonate1.58630
Polystyrene1.59031
Water (at 37ºC)1.33156
Aqueous and vitreous (at 37ºC)1.33456
References in periodicals archive ?
"n" is the refractive index of the high index lens in question Plastic Curve Variation Factor (CVF) Reduction in lens lenses Relative to CR39 edge thickness CVF = (1.498-1)/(n-1) 1.586 0.85 15% 1.600 0.83 17% 1.740 (3.67 33% Glass Curve Variation Factor (CVF) Reduction in lens lenses Relative to Crown edge thickness CVF = (1.523-1)/(n-1) 1.7 0.75 25% 1.8 0.65 35% 1.9 0.55 45% Table 2 Optical quality of various lens materials in terms of constringence (Abbe number).
* Use materials with as high as possible refractive indices and Abbe numbers
According to Dooley, the new material has very low birefringence, the stress distortion inherent in lens manufacturing, and an Abbe number of 46.
Performance NXT sunlens have a lower refractive index, internal stress, and chromatic dispersion (Abbe number) than polycarbonate, resulting in lower surface reflection and rainbow effect, higher definition and sharper images.