Rotational symmetry in CBED patterns

A method for efficient detection of the dominant local rotational symmetry in grey level images of CBED patterns is described. The general approach is to define a local measure of rotational symmetry that transforms the symmetry detection problem to an optimization problem, and obtain the symmetric regions by an efficient global optimization algorithm. In this paper, we present the correlation function as the measure of rotational symmetry. The value depends on the center of the supporting region, its size, and the rotational angle. The genetic algorithm is taken to search the global maximum of the rotational symmetry. The method is shown in experiments to be both effective and quick.