John Dollond

See also: Dollond

John Dollond (June 10th 1706 - November 30th 1761) is a British engineer-optician .

Dollond is the son of a French refugee Huguenot, a silk manufacturer of Spitalfields, London or it is born in 1706. It continues the trade of his father but in same time acquires knowledge in Latin, Greek, Mathématiques, Physique, Anatomie inter alia. In 1752 it gives up the trade of the Soie and joint with his/her oldest son, Peter Dollond (1730-1820) which in 1750 starts to manufacture instruments of Optique.

In 1747 whereas he is still an optician amateur, he writes a criticism with Leonhard Euler according to which the Chromatic aberration could be corrected. Dollond on its side, starting from work of Newton on this subject, considers that it is impossible. However after having received the summary of a report of Samuel Klingenstierna, a Swedish mathematician and astronomer, it doubts the precision of the experiments of Newton. Klingenstierna shows, starting from purely geometrical considerations, that the results of Newton contradict other facts universally accepted on the Réfraction. Dollond carries out to him even a series of experiments and accepts that the chromatic aberration can be corrected. In 1758 it publishes Account off different nap experiments concerning the refrangibility off light (Phil. Trans., 1758) describing its experiments and the advance of the development of achromatic lenses by the combination of concave and convex lenses. One often credits Dollond, wrongly, for the invention of the achromatic lenses. However, before him, Chester More Hall, a man of law, optician amateur, also solved the problem. Hall decides to maintain the secrecy on its invention and makes manufacture the 2 lenses necessary, one in Verre flint and one in glass crown by two different opticians. By a singular chance, these opticians sub-contract work with the same manufacturer George Bass. Low the interest of this technique includes/understands but he either does not take a patent on the invention. In the Années 1750 Dollond meets Bass which tells him the history, Dollond creates its own version of the lenses and the brevette. One can consider that Dollond popularized the achromatic lenses rather than he did not invent them.

Dollond as wrote two articles on the improvements as it brings to the heliometer, an apparatus to measure the apparent Diamètre Sun and Planet S.

Dollond obtains the Médaille Copley in 1758 for its report on the correction of the chromatic aberration. Three years later he is elected member of the Royal Society.

He dies the November 30th 1761 after an attack of apoplexy. Its name perdure in that of the company Dollond & Aitchison specialized nowadays in medical optics: glasses, contact lenses etc

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