RETRIEVAL OF OBJECT INFORMATION FROM ELECTRON-DIFFRACTION .1. THEORETICAL PRELIMINARIES

Electron holography and other wave reconstruction techniques allow one to determine directly the scattered wave function at the exit surface of an object up to the information limit of the electron microscope. Based on the knowledge of the reconstructed complex electron wave and using an discretized form of the diffraction equations, this in princi ple enables the direct retrieval of the atomic displacements, caused b y a crystal lattice defect, relative to the atom positions of the perf ect lattice. A special inverse problem of electron scattering can be d educed considering solely the atomic displacements, which are given by the zeros of a function with an incompletely known Fourier spectrum. The fundamental relations are described, with the problems of solving the ill-posed Fourier transform being discussed.