Study on coma aberration correction technique for imaging systems of optical and electron microscope by the use of image processing

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The present study is based on results of past studies of 'Grant-in-aid for scientific research'. The aim of this study is the establishment of the aberration correction theory for coma and higher order anti-symmetric wave aberrations in transmission electron microscopes. And also, the construction of a real-time on-line coma aberration correction apparatus, based on the image processing, is the second aim of this study.According to these aims, a generalized aberration correction theory for coma aberration was obtained by extending the tree dimensional (3D) imaging theory to the case of the anti-symmetric wave aberration. And a simple correction filter in the Fourier space, derived from this aberration correction theory, is proposed in the first stage (1999) of this study. Using the extended 3D imaging theory, computer simulations of the coma aberration correction were also achieved to examine the influence of the non-linear imaging terms in which the present coma aberration correction … More is not applicable. In this simulation, the influence of non-linear imaging terms begun to exhibit obvious for phase objects of the phase delay greater than 1/20 λ.The present coma aberration correction filter is based on the simple 2D phase correction in the Fourier space. The system design and the program coding of the real-time on-line coma aberration correction apparatus were carried out in the next stage (2000). By the reason of difficulties on the program coding, a LAN connected separate on-line correction system was designed for the video image acquisition and the coma aberration correction, instead of the integrated system using one PC, originally expected. The processing rate of the constructed on-line coma aberration correction apparatus was about 30 sec/frame. Although this processing rate is very low compared with the first aimed value (several frames / second), other characteristics as the online coma aberration corrector were well confirmed in this study. We will be re-planning the system design as an integrated system using one PC. Less