Measurement method of aberration from Ronchigram by autocorrelation function

Abstract

Aberrations up to the fifth-order were successfully measured using an autocorrelation function of the segmental areas of a Ronchigram. The method applied to aberration measurement in a newly developed 300 kV microscope that is equipped with a spherical aberration corrector for probe-forming systems. The experimental Ronchigram agreed well with the simulated Ronchigram that was calculated by using the measured aberrations. The Ronchigram had an infinite magnification area with a half-angle of 50 mrad, corresponding to the convergence angle of a uniform phase.