See Doublet, 6 and 7.
Source: Webster's dictionaryAn alternative to achromatic doublets is the use of diffractive optical elements. Source: Internet
German gothic armour arming doublets were generally shorter than Italian white armour doublets, which could extend to the upper thigh. Source: Internet
Internal structure A eukaryotic flagellum is a bundle of nine fused pairs of microtubule doublets surrounding two central single microtubules. Source: Internet
In western languages such as Spanish, Portuguese and Catalan, doublets and triplets arose such as Portuguese aqui, acá, cá "(to) here" (accu-hīc, accu-hāc, eccu-hāc). Source: Internet
Note that these two parameters which enter into the equations for design of achromatic doublets are exactly what is plotted on an Abbe diagram. Source: Internet
Silk from the hornet cocoon contains doublets about 10 µm across, with cores and coating, and may be arranged in up to 10 layers, also in plaques of variable shape. Source: Internet