Theoretical basis of image-deconvolution method for structure images of thin crystals

Abstract

The basis of the ‘image deconvolution method’ for processing multi-beam lattice images from thicker crystals up to 10–15 nm is theoretically considered including the dynamical diffraction effect in the crystals and assuming the weak scattering approximation in the image intensity calculation. It is shown that dividing two-dimensional Fourier transform of the lattice images by the imaginary part of contrast transfer function is still effective in correcting the image contrast modifications introduced in actual images, if modified defocus values are employed. Based on the consideration, the essential features of structure images are clarified, and an experimental method is proposed for obtaining the image contrast free from the effects of spherical aberration of objective lens and dynamical diffraction.