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US 5,708,274 AGranted
Curvilinear variable axis lens correction with crossed coils
AssigneeInternational Business Machines Corporation
InventorsGuenther O. Langner, Werner Stickel
Life of this patent
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Abstract
A charged particle lens has an axis that is shifted to follow the central ray of the beam as it is deflected through the lens creating, in effect, a variable curvilinear optical axis for the lens and introducing aberrations having depending on the object size and the distance off the lens symmetry axis. These aberrations are corrected by a set of coil pairs tilted with respect to the system axis, which generate compensating aberrations of the same type.
Claims11
A curvilinear axis correction system for charged particle optical lenses comprising:
- a lens having field generating means disposed about a system axis and extending a lens length along said system axis for producing a focusing field to focus a charged particle beam;
- and
- axis-shifting means for producing a set of axis compensation fields within said lens, said set of axis compensation fields being substantially uniform in a plane perpendicular to said system axis and varying in magnitude as a function of position along said system axis, said function of position being dependent on a trajectory of a central ray of said charged particle beam and said set of axis compensation fields having a magnitude sufficient to cancel a radial component of said focusing field, whereby a variable axis of said focusing field is substantially coincident with said trajectory of said central ray of said charged particle beam;
- characterized in that:
- an intersection angle between said trajectory of said central ray of said charged particle beam and said focusing field at an axis-shifting plane exceeds an intersection threshold value and said system further includes at least one tilt means for applying at least one tilt field in addition to said set of axis compensating fields.
2 more elements
Dependencies are inferred from the claim text.