Preliminary experiments for development of real-time defocus-image modulation processing electron microscope

Preliminary experimental results for realizing real-time defocus-image modulation processing in a high-resolution transmission electron microscope are reported in terms of equivalence between objective lens current modulation and accelerating voltage modulation, precise measurement of the voltage centre axis and rapid control of accelerating voltage. The equivalence between the two modulations is clearly demonstrated by showing the similarities of the two respective Then diagrams. The accelerating voltage change of 1 V leads to 8.75 nm focus change in the present electron microscope. A precise method to measure the misalignment of the voltage centre axis is proposed on the basis of three dimensional Fourier analysis using through-focus images. A floating type accelerating voltage generator system was newly designed in order to make the rapid modulation as precisely as possible, which is essentially important for developing a real-time defocus-image modulation processing electron microscope.