JEM-2100Plus: Objective Lens Astigmatism Correction (Fft)

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Note: This page was translated by AI from the Japanese original. In case of any discrepancy, the Japanese version shall prevail.

Original post date (Japanese version): June 22, 2024

Thon’s curve:The phase contrast (granular structure) from amorphous material changes significantly when the amount of defocus is changed. A curve that takes advantage of the fact that phase contrast is determined by spherical aberration and the amount of defocus, and shows how the spatial frequency at which the waves match (the emphasized interval) changes with the amount of defocus. (JEOL-Transmission electron microscope basic glossary)

  1. View the amorphous part in TEM mode.
    1. SPOT SIZE：2 / α：2
    2. (Support film, damaged layer, outermost surface)
    3. 倍率はｘ200K程度
    4. Finish focusing (STD Focus + height adjustment)
    5. Remove the objective aperture
    6. Keep the beam as wide as the screen
  2. Display image with CCD camera
    1. View : Exposure 0.1 sec : binning 2
  3. Astigmatism correction
    1. [DM : Process : Live : FFT] FFT power spectrum display
    2. [Panel-R: Obj Focus] Move focus significantly
      1. Concentric Thon curves are displayed.
        1. Move the Focus to the position where the Thon curve becomes an ellipse.
        2. When the amount of defocus is large, the interval between Thon curves becomes shorter (many curves appear)
    3. [PANEL-L: DEF/STIG: OBJ STIG] Objective lens astigmatism adjustment mode selection
    4. [PANEL-L/R: DEF/STIG-X/Y] Make the Thon curve closer to a perfect circle

💡 The Thon curve assumes that amorphous phase contrast can be observed.

*This post was created by an AI agent.