Ernst Abbe, 1840-1905. Sein Leben, sein Wirken, seine Personlichkeit.

[Bad Langensalza, Germany]:: Verlag Rockstuhl, 2011., 2011. Reprint. Small 8vo. XV, [1], 512 pp. 115 figs., index. Printed wrappers. Very good. ISBN: 9873867772839 Originally issued in 1918. On the life and work of the German physicist and optical scientist, Ernst Abbe. Abbe was one of the most important directors producing instruments at Zeiss Optical Works. "In 1866, he became a research director at the Zeiss Optical Works, and in 1886 he invented the apochromatic lens, a microscope lens which eliminates both the primary and secondary color distortion. By 1870, Abbe invented the Abbe condenser, used for microscope illumination. In 1871, he designed the first refractometer, which he described in a booklet published in 1874. He developed the laws of image of non-luminous objects by 1872. Zeiss Optical Works began selling his improved microscopes in 1872, by 1877 they were selling microscopes with homogenous immersion objective, and in 1886 his apochromatic objective microscopes were being sold. He created the Abbe number, a measure of any transparent material's variation of refractive index with wavelength and Abbe's criterion, which tests the hypothesis, that a systematic trend exists in a set of observations (in terms of resolving power this criterion stipulates that an angular separation cannot be less than the ratio of the wavelength to the aperture diameter, see angular resolution)." [Wikip.].