Joseph von Fraunhofer (1787-1826), German physicist. Fraunhofer began his career as an apprentice to a glassmaker, progressing to the Optical Institute at Benediktbeuern, Bavaria, Germany. Extensive study and careful techniques enabled him to produce the finest optical glass in the world, and in 1818 he became director of the institute. He invented the spectroscope for measuring the properties of light, which led him to discover dark lines, now known to be atomic absorption lines, in the solar spectrum. He invented the diffraction grating, for measuring the wavelength of light, and discovered that different stars have different spectra. His early death was caused by heavy-metal vapours from his glass-blowing trade.