THEORETICAL BASIS OF IMAGE-DECONVOLUTION METHOD FOR STRUCTURE IMAGES OF THIN-CRYSTALS

The basis of the 'image deconvolution method' for processing multi-bea m 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 transf orm of the lattice images by the imaginary part of contrast transfer f unction is still effective in correcting the image contrast modificati ons introduced in actual images, if modified defocus values are employ ed. Based on the consideration, the essential features of structure im ages are clarified, and an experimental method is proposed for obtaini ng the image contrast free from the effects of spherical aberration of objective lens and dynamical diffraction.