Barr & Stroud Limited was a pioneering Glasgow optical engineering firm. They played a leading role in the development of modern optics, including rangefinders, for the Royal Navy and for other branches of British Armed Forces during the 20th century. There was a non-military arm of the company which made medical equipment, like photocoagulators and electronic filters, some of which were used by the BBC. The company and its intellectual property passed through Pilkington group to Thales Optronics. The Barr and Stroud name was sold on to an importer of optical equipment, who use the trademarked name for a line of binoculars and similar instruments.