Method of directly deriving amplitude and phase information of an object from images produced by a high-resolution electron microscope

摘要

A high-resolution electron microscope (1) comprising a detection system (11), an image processing system (13) and an effective electron source (3) ensuring a comparatively small thermal energy spread of the electrons to be emitted is suitable for executing a method for directly deriving amplitude and phase information of an object (17) in the form of an electron wave function &phgr;. To this end, a number of images of an object (17) are recorded by means of a high-resolution electron microscope (1) in image planes (19) with defocus values which differ only slightly. Thus, a substantially continuous series of images is formed as a function of the defocus value, resulting in a substantially three- dimensional image area. A quasi-three-dimensional Fourier transformation is performed thereon in order to separate linear and non-linear image information for the reconstruction of the electron wave function. In practice a two-dimensional Fourier transformation is applied to the recorded images which are subsequently multiplied by a complex weighting factor, followed by summing. As a result, the linear information is concentrated on two spheres in the Fourier space, the non- linear information being uniformly distributed across the Fourier space.