Underfocusing Objective Lens in TEMs
- Practical Electron Microscopy and Database -
- An Online Book -

http://www.globalsino.com/EM/  



 
This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.
 

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The aberration coefficient C1 in TEMs is almost always present since it is used to reduce the effects of the spherical aberration by slightly underfocusing the objective lens (corresponding to a negative C1).

Generally speaking, spatial resolution in EMs (electron microscopes) is very sensitive to objective astigmatism. Therefore, it is necessary to correct it carefully. In TEM imaging, objective astigmatism is conveniently adjusted by viewing the Fresnel fringes near the edge of a small hole under overfocus condition.

 

 

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