| 摘要 |
PROBLEM TO BE SOLVED: To provide a cathode lens which can adjust an electric field intensity on a sample surface so as to reduce an aberration most according to a kind of a sample, a state of a surface thereof, and a requested energy resolution. SOLUTION: A potential of -Vs is given to an upper electrode 14, and an electric field E1 is generated on the sample surface by the potential difference between the upper electrode 14 and an anode 11. The potential of -aVs (0<a<1) is given to a lower electrode 13, and an electric field E2 is generated on the sample surface by the potential difference between the upper electrode 14 and the lower electrode 13. This electric filed E2 has an electric filed with direction opposite to the electric filed E1. The figure shows a distribution on an equipotential surface when an electric field on an optical axis on the sample surface is strictly set to 0 by adjusting the potential of lower electrode 13. It is only one point on the optical axis on the sample surface that the electric field is 0 and the electric field intensity stands at the same time as parting the electron from the sample, and an ideal state is made.
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