Phasenkontrast bei der Abbildung biologischer Objekte

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Abstract
The significance of phase contrast for the reproduction of structures in the electron microscopic image is shown in cross sections of medullary nerve fibers which may be shown with optimal contrast when other structural elements are out of focus. Thus, the image of this membrane system, out of focus by about 3.4[mu], shows the membranes at a distance of 110 A with clearly higher contrast than the image in focus, with a concomitant evident reduction of membrane width. An image about 5[mu] out of focus reveals, in strong contrast with the first mentioned membranes, another middle line at a distance of 55 A. In this connection it was pointed out that the image of any other object whatever with a periodic structure at a distance of 110 A, about 5[mu] out of focus may also show a half period of 55 A, even though the object has no such periodicity in its structure.