Research on an Improvement of Resolution of Electron Microscope by Means of Maximum Entropy Image Restoration.

点击翻译按钮获取中文摘要

1. Construction of Maximum Entropy (ME) Restoration System : A system for acquisition and ME restoration of conventional transmission electron microscope (CTEM) images was constructed by using a high quality scanner and by an implementation of ME restoration programs in a workstation instead of a mainframe used before.2. Restoration of Scanning Transmission Electron Microscope (STEM) Images : A newly developed ME method which was designed to realize a random spatial distribution (RSD) of the inferred noise as a constraint in maximization of the image entropy, was applied to STEM images with low signal-to-noise ratio (SNR). A specimen of ferritin particles was used as a typical example of spatially extended objects for which conventional ME method failed to provide successful restoration. In was found that the SNR of the image was increased by processing with RSD constraint. The method was also applied to dark-field STEM images to study effects of the ME restoration on images blurred by a broad electron probe. With a probe having a relatively large diameter of 6.2 nm, ferritin particles with the original diameter of about 7 nm were observed with an average diameter of 12 nm. By processing the image with the improved ME method, the particle size was reduced to 9.8 nm in diameter so that closely positioned particles, not resolved in the original image, were clearly resolved with a high SNR.3. Restoration of CTEM Images : The improved ME method was applied to a model image of weak phase objects. The blurring and the noise were simultaneously reduced for images of disk objects with a large area as well as point objects. A largely defocused noisy CTEM image of ferritin particles was processed in practice. The improved ME method yielded a successfully restored image with decreased blurring and increased SNR.