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 micr oscope are reported in terms of equivalence between objective lens cur rent modulation and accelerating voltage modulation, precise measureme nt of the voltage centre axis and rapid control of accelerating voltag e. 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 th e present electron microscope. A precise method to measure the misalig nment of the voltage centre axis is proposed on the basis of three dim ensional Fourier analysis using through-focus images. A floating type accelerating voltage generator system was newly designed in order to m ake the rapid modulation as precisely as possible, which is essentiall y important for developing a real-time defocus-image modulation proces sing electron microscope.