Abstract: An electron microscope and a method for measuring the defocus spread or the limiting resolution of an electron microscope takes advantage of the fact that, in the case of tilted illumination, any aberration that may be present and the defocus spread of the electron microscope anisotropically change the intensity distribution in the diffractogram. In particular, the envelope of the diffractogram is anisotropically narrowed. If both the tilt of the electron beam and any aberration that may be present are known, and the focus distribution is assumed to be Gaussian-shaped, the defocus spread of the electron microscope is the only parameter still unknown that influences the anisotropic changes in intensity distribution. Quantitative conclusions as to the defocus spread can thus be drawn from the changes. However, the focus distribution can also be determined from the anisotropic narrowing without the use of a model, and without a priori assumptions about the shape thereof.

Abstract: Disclosed is a method for measuring the similarity of two-dimensional images, at least one image exhibiting an additional signal, the location dependence or symmetry properties of which are known at least approximately. The images are partitioned into mutually identical subimages such that the extension of at least one subimage in the direction of the gradient of the additional signal is smaller than the extension of this subimage in the direction perpendicular thereto. The subimages are compared separately, and the results of all comparisons are combined to form the measurement result for similarity. As a result, the method becomes insensitive to variations in the additional signal. The method is particularly suited for the determination of defocusing and astigmatism of an electron-microscopic image. For this purpose, it is important to compare the similarity of an experimentally measured image to simulated images, which were generated using defined defocusing and astigmatism values.

Abstract: An electron microscope and a method for measuring the defocus spread or the limiting resolution of an electron microscope takes advantage of the fact that, in the case of tilted illumination, any aberration that may be present and the defocus spread of the electron microscope anisotropically change the intensity distribution in the diffractogram. In particular, the envelope of the diffractogram is anisotropically narrowed. If both the tilt of the electron beam and any aberration that may be present are known, and the focus distribution is assumed to be Gaussian-shaped, the defocus spread of the electron microscope is the only parameter still unknown that influences the anisotropic changes in intensity distribution. Quantitative conclusions as to the defocus spread can thus be drawn from the changes. However, the focus distribution can also be determined from the anisotropic narrowing without the use of a model, and without a priori assumptions about the shape thereof.

Abstract: Disclosed is a method for measuring the similarity of two-dimensional images, at least one image exhibiting an additional signal, the location dependence or symmetry properties of which are known at least approximately. The images are partitioned into mutually identical subimages such that the extension of at least one subimage in the direction of the gradient of the additional signal is smaller than the extension of this subimage in the direction perpendicular thereto. The subimages are compared separately, and the results of all comparisons are combined to form the measurement result for similarity. As a result, the method becomes insensitive to variations in the additional signal. The method is particularly suited for the determination of defocusing and astigmatism of an electron-microscopic image. For this purpose, it is important to compare the similarity of an experimentally measured image to simulated images, which were generated using defined defocusing and astigmatism values.