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US 5,965,894 AGranted
Method of operating a particle-optical apparatus
AssigneeU. S. Philips Corporation
InventorsMarcellinus P.C.M. Krijn, Alexander Henstra
Life of this patent
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AssigneeU. S. Philips Corporation
InventorsMarcellinus P.C.M. Krijn, Alexander Henstra
Estimating the term…
Electron-optical, rotationally-symmetrical lenses inevitably exhibit spherical and chromatic aberration which usually determine the limit of the resolution. Such lens aberrations cannot be eliminated by compensation by means of rotationally-symmetrical fields. In order to enhance the resolution nevertheless, it has already been proposed to reduce said lens aberrations by means of a Wien-type corrector. Such a configuration must satisfy very severe requirements as regards manufacturing precision, mechanical and electrical stability and alignment of the various elements relative to one another. Consequently, it is extremely difficult to perform readjustment of the electron-optical apparatus by means of such a corrector in the case of changing circumstances. According to the invention there is provided a combination of a correction unit and a doublet to be corrected. By constructing the objective to be corrected as a doublet 5 and by independently controlling the two lenses 6 and 8 of the doublet 5, the setting of the correction unit 28 can remain unchanged, it being possibly to vary the free object distance and the electron voltage nevertheless during operation of the electron-optical apparatus. FIG. 1.
A method of operating a particle-optical apparatus, which apparatus includes:
A particle-optical apparatus comprising:
Dependencies are inferred from the claim text.