Radiant energy – With charged particle beam deflection or focussing – Magnetic lens
Reexamination Certificate
2005-03-01
2005-03-01
Font, Frank G. (Department: 2883)
Radiant energy
With charged particle beam deflection or focussing
Magnetic lens
C250S3960ML, C250S305000, C250S311000, C250S398000
Reexamination Certificate
active
06861651
ABSTRACT:
The invention relates to an electron-optical corrector for eliminating third-order aberrations, such as spherical aberrations, field curvature and off-axis astigmatism; said corrector being devoid of third-order off-axis coma, third-order distortion and first-order chromatic aberration of the first degree. The corrector has a construction which is symmetrical about the central plane in the direction of the linear optical axis. A hexapole S1of length l1is first positioned in the direction of the beam path, followed by a circular lens R1, a hexapole S2of length l2and subsequently a circular lens R2which is followed by a third hexapole S3with the same strength with the same strength of the hexapole S1and double the length of the latter l3=211. The separation of the two circular lenses R1, R2and the distance from the circular lens to the first hexapole S1is chosen in such a way that the internal plane of S1comes to rest in the front principal focus of the circular lens that is positioned downstream and the center of the hexapoles S2and S3is located on the focal plane. Additional elements of the corrector also follow in sequence, said elements being symmetrical about the central plane Zmof the hexapole S3.
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Birch & Stewart Kolasch & Birch, LLP
Carl Zeiss NTS GmbH
El-Shammaa Mary
Font Frank G.
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