Radiant energy – Inspection of solids or liquids by charged particles – Methods
Patent
1990-11-06
1992-01-28
Anderson, Bruce C.
Radiant energy
Inspection of solids or liquids by charged particles
Methods
250311, 250397, H01J 3726
Patent
active
050846183
ABSTRACT:
Autofocus method and apparatus capable of quickly detecting the focal point in an electron microscope in spite of the magnetic aftereffects of the ferromagnetic substance forming the objective lens. The autofocus method is initiated by causing the electron beam emitted from the microscope to hit a specimen at a first angle. Under this condition, the excitation current fed to the objective lens is continuously varied between values. At the same time, a video signal obtained from the resulting projected image is sampled at fixed intervals to obtain a first set of data. Then, the beam is caused to hit the specimen at a second angle. Under this condition, the excitation current fed to the objective lens is continuously varied between values. Simultaneously, a video signal produced from the resulting projected image is sampled at fixed intervals to obtain a second set of data. These two sets of data are compared to find the focal point.
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Anderson Bruce C.
Jeol Ltd.
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