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Correlation averaging of two-dimensional crystals: basic strategy and refinements

1986; Cambridge University Press; Volume: 44; Linguagem: Inglês

10.1017/s0424820100142323

2690-1315

W. Baumeister, Reinhard Rachel, R. Guckenberger, R. Hegerl,

Advanced X-ray Imaging Techniques

Introduction Correlation averaging (CAV) is meanwhile an established technique in image processing of two-dimensional crystals /1,2/. The basic idea is to detect the real positions of unit cells in a crystalline array by means of correlation functions and to average them by real space superposition of the aligned motifs. The signal-to-noise ratio improves in proportion to the number of motifs included in the average. Unlike filtering in the Fourier domain, CAV corrects for lateral displacements of the unit cells; thus it avoids the loss of resolution entailed by these distortions in the conventional approach. Here we report on some variants of the method, aimed at retrieving a maximum of information from images with very low signal-to-noise ratios (low dose microscopy of unstained or lightly stained specimens) while keeping the procedure economical.