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GP: Fachverband Geschichte der Physik

GP 6: Tools and Technologies of physics research

GP 6.3: Vortrag

Dienstag, 19. März 2019, 15:15–15:45, HS 9

Pushing wide-field microscopy to the limit around 1900 — •Timo Mappes — Deutsches Optisches Museum (D.O.M.), Carl-Zeiss-Platz 12, 07743 Jena, Germany — Friedrich-Schiller-Universität Jena, 07737 Jena, Germany

Experimenting with the parameters of Abbe's resolution limit formula, scientific studies on enhancing the numerical aperture (N.A.), and reducing the wavelength were performed. As such, objectives with N.A. of up to 1.6 were introduced in 1889 and successfully applied by leading diatomists. However, these objectives were eventually limited in use by the delicate mounting of their front lens, and the toxic and aggressive nature of the required immersion liquid. Still, these systems were re-introduced for conoscopy several decades later.

In 1902 wide-field microscopy at easily accessible short wavelengths was carried out, namely with sparks of Cd (275 nm) and Mg (280 nm). The entire optical train had to be manufactured out of fused silica or rock crystal. The systems were optically corrected for 275 nm only and consequently called "Monochromat". Being in the middle ultra violet the numerical aperture had to be re-defined to enable the use of Abbe's resolution limit formula, and "relative Apertur" (r.A.) was introduced for calculation. While the increase in resolution was outstanding, the images had to be caught on film to make them visible. Thus, the entire procedure was very time-consuming and not fitting for applications in biological or medical research. However, fluorescence was discovered with this setup, while initially being identified as a disturbing side-effect.