The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 23, 1993
Filed:
Mar. 04, 1991
Applicant:
Inventor:
Mark A Gesley, Oakland, CA (US);
Assignee:
Etec Systems, Inc., Hayward, CA (US);
Primary Examiner:
Int. Cl.
CPC ...
H01J / ;
U.S. Cl.
CPC ...
250398 ; 2503 / ; 2504922 ;
Abstract
A field emission source is used in conjunction with a three element asymmetric lens system to provide an electron gun having greater magnitude beam currents focused on a smaller spot size than has been previously possible for intermediate energy beams. The three element asymmetric lens system has a lower spherical aberration than prior art electrostatic guns and a very low chromatic aberration coefficient, enabling precise focusing of beams with large currents and energy spreads. The electron gun produces high current densities in beam focused on small spot areas, despite the relatively large acceptance angle and energy spread of the source beams.