Ernst Karl Abbe (23.I 1840 - 14.I 1905) was a German optical physicist. Born in Eisenach. He studied at the universities of Jena and Göttingen, taking his doctorate at the latter in 1861. From 1870 he worked at the University of Jena (from 1879 as professor, and from 1877 to 1901 as director of the observatory). In 1866 he began to work with C. Zeiss, and in 1876 became his partner. After Zeiss's death he became the effective owner of his optical workshops, but he renounced the rights of an owner and drew up a special charter for the running of the enterprise.His research was in optics. He developed the theory of image formation in the microscope (1872) and the technology of important branches of the optical and mechanical industry. He constructed the first modern optical microscope (1878), showed that the resolving power of the optical microscope is limited by the wavelength of light, and created a number of other optical instruments (the Abbe refractometer, the achromatic objective, the Abbe condenser and others). He improved Fizeau's interference method (1844).