Technology for Fundamental Improvement of an Extremely Low-Quality Video Signal for Use in Fine Focusing and Astigmatism Correction in Scanning Electron Microscopy

Figure 6

Test of system robustness against noise during fine focusing operation for extremely noisy SEM images. (a) Unprocessed TV-scan image acquired at 3 pA (300,000x). The graph of (a) does not work at all. (b) The image processed (focused) using the procedure described in Figure 5(b) works well, as expected. (c) Processed image (defocused) of the identical view. The graphs in (b) and (c) are continuous. To provide further stabilization, the moving average (average of four points on a graph for the focusing operation) and the frame integration (integration of four TV-scan images) were also used for (d) and (d) (fine focusing) and for (e) and (e) (astigmatism correction). (f) and (f) show the results that confirm the validity of the method used in Figure 3. (g) Slow scan image. (h) Additional slow scan image of Au-coated silica particles. See text for details. The bars represent 0.14 μm (a–f), 0.7 μm (g), and 0.42 μm (h).