Carl-zeiss-stiftung

F Peter Ottensmeyer

Wilhelm Egle

Albrecht Rilk

A transmission electron microscope is disclosed, having an electron-energy spectrometer, a first imaging stage of four electron lenses in front of the spectrometer, and a second imaging stage of two more electron lenses following the spectrometer. The parts are so arranged, according to the disclosed structure, and so operated, according to the disclosed method, that a large range of magnifications can be obtained while the object or specimen to be examined remains in a fixed location, without having to refocus when the magnification is changed. The change in magnification occurs by changing the operation of the first imaging stage. The second imaging stage operates at a substantially fixed magnification, its magnification being changed, if at all, only to accommodate the size of the output image from the second stage to size of the available working area of the detector in the final image plane (fluorescent screen, photographic film, or electronic detector). The first stage, at all magnifications, always images the object or an image of a diffraction pattern of the object into the input image plane of the spectrometer and an image of the electron source into the input crossover plane of the spectrometer. The spectrometer is of the prism-mirror-prism type, and improved results are obtained by making the entrance and exit surfaces of the prism curved rather than planar.

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Don Mills, Canada

F Peter Ottensmeyer