THE VIDEOGRAPHIC METHOD - A NEW PROCEDURE FOR THE SIMULATION AND RECONSTRUCTION OF REAL STRUCTURES

The videographic method is a simulation and reconstruction procedure that uses a statistical mathematical approach and computer graphics to aid the interpretation of scattering (X-ray, electron, neutron) from a disordered crystal. Based on the principles of optical transforms, and in contrast to it, atoms with different scattering power are represented as picture elements (pixels) with different grey levels. Compared with optical transforms, this method has the special advantage that holes of infinitely small radii can simulate different scattering powers in a mask. With the application of a statistical mathematical approach (combination probabilities), various scatterers, e.g. atoms, structure variants or domains, can be distributed in a two- or three-dimensional model. A Fourier transformation of the simulated model (diffraction pattern) can be calculated in a few seconds using an array processor and displayed for comparison with experiments. Real-structure image reconstruction can also be performed by amplitude and phase manipulation. As a starting model for a reconstruction, a randomly disordered structure is assumed. Under this assumption, a monotone diffuse background is obtained in the diffraction pattern. The principal idea in a reconstruction of an unknown real structure is that the diffuse regions of a partly ordered structure are a subset of the monotone diffuse background for a random disorder.