Dollond, John(dŏl`ənd), 1706–61, English optician and inventor. A silk weaver, he taught himself languages, mathematics, and science, becoming a noted scholar as well as a scientist. He invented the achromatic lens, which led to the construction of telescopes free of color fringes, and the heliometer, used in astronomical measurement.
Born June 10, 1706; died Nov. 30, 1761. English optician.
In 1758, Dollond received a patent to produce achromatic objectives for telescopes. The first achromatic objectives were made in England as early as 1733, but they were highly imperfect. Dollond, who at first shared Newton’s opinion that it was impossible to make achromatic objectives, began to study the question in the light of L. Euler’s theory. After lengthy experiments he found a successful combination of lenses with good achromatic properties (a converging [positive] lens of crownglass and a diverging [negative] lens of flintglass). Dollond’s telescopes rapidly became popular.