 Joseph von Fraunhofer

Joseph von Fraunhofer combined precision manufacture of optical glass with quantitative spectroscopy. He systematically mapped dark lines in the solar spectrum and used them as reproducible reference points for comparing refraction in different glasses. His diffraction gratings supplied another way to separate and measure wavelengths. The Fraunhofer lines thus served an immediate engineering purpose before their later interpretation as signatures of absorbing matter: they let optical experiments return to the same identifiable spectral features.^[ref]

Joseph von Fraunhofer (1787–1826) was a German physicist and optical engineer who made significant contributions to the field of optics. He is best known for his work in the development of high-quality optical instruments, particularly telescopes and microscopes. Fraunhofer is especially renowned for his discovery of the Fraunhofer lines—dark lines in the solar spectrum that result from the absorption of specific wavelengths of light by elements in the Sun's atmosphere.