The Cooke triplet was the first lens which was quite well color corrected for two colors (achromatic lens) and also corrected against astigmatism (anastigmat), patented in 1893 by Dennis Cooke. The only later basic efforts made in lens history were the correction for three colors (apochromatic lens), the coating against flares, and the mass-production of aspherical lenses.
|The combination of two convex lens elements made of crown glass with a concave|
one which is made of flint glass is known since 1765 as a means against chromatic
|Cooke Triplet lens 1916|
image by Geoff Harrisson (Image rights)