Achromatic doublet (lens power)


An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration. Achromatic lenses are corrected to bring two wavelengths (typically red and blue) into focus in the same plane. The achromatic doublet is composed of two individual lenses made from glasses with different amounts of dispersion. The one of the elements is a negative element made out of flint glass , which has relatively high dispersion, and the other is a positive . The lens power of the elements is related to the Abbe number V (for the reciprocal of the glass dispersion)
(Optical power (also referred to as dioptric power, refractive power, focusing power, or convergence power) is the degree to which a lens, mirror, or other optical system converges or diverges light. It is equal to the reciprocal of the focal length of the device).
(The Abbe number, also known as the V-number or constringence of a transparent material, is a measure of the material’s dispersion. For example, flint glass has V < 50 and crown glass has V > 50. Typical values of V range from around 20 for very dense flint glass, around 30 for polycarbonate plastics, and up to 65 for very light crown glass, and up to 85 for fluor-crown glass ).

Related formulas


p1The power of the first lens (m-1)
V1 Abbe number of the first lens (dimensionless)
p2The power of the second lens (m-1)
V2 Abbe number of the second lens (dimensionless)