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The technique described here, utilizing the sharpness concept, is facilitated by the use of the FFT techniques to analyze the electron micrograph to obtain the evaluation. This is not the first application of Fourier techniques to SEM images, but it is the first integrated approach considering the sample, computer analysis and measurement algorithm. This technique can be used to check and optimize two basic parameters of the primary electron beam, the focus and the astigmatism and it facilitates the periodic resolution determination of the SEM in an objective and quantitative form.