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TEM Basics

 
Astigmatism
    N
 

The image of a hole in an amorphous carbon film illuminated with a parallel beam showing that

  • with the objective lens underfocused (0-2) a bright Fresnel fringe is visible inside the hole;
  • with the objective lens overfocused (4 - 6) a dark fringe is visible inside the hole;
  • at exact focus (3) there is no fringe;
  • the appearance of the image varies as the x and y correction (-, OK or +) is altered

1. Did you try to do the correction at the highest available magnification?
2. What are the correctors doing to the magnetic field of the objective lens?

 
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  Electron-atom interactions | Electron gun | Lenses
 

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