John Dollond - Priority of Invention

Priority of Invention

John Dollond was the first person to patent the achromatic doublet. However, it is well known that he was not the first to make achromatic lenses. Optician George Bass, following the instructions of Chester Moore Hall, made and sold such lenses as early as 1733. In the late 1750s, Bass told Dollond about Hall's design; Dollond saw the potential and was able to reproduce them.

Dollond appears to have known of the prior work and refrained from enforcing his patent. After his death, his son, Peter, did take action to enforce the patent. A number of his competitors, including Bass, Benjamin Martin, Robert Rew and Jesse Ramsden, took action. Dollond's patent was upheld, as the court found that the patent was valid due to Dollond's exploitation of the invention while prior inventors did not. Several of the opticians were ruined by the expense of the legal proceedings and closed their shops as a result. The patent remained valid until it expired in 1772. Following the expiry of the patent, the price of achromatic doublets in England dropped in half. More details on this invention are in History of the telescope.