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:
Feb. 09, 1982
Filed:
Oct. 03, 1979
Applicant:
Inventor:
Kenneth C Smith, Cambridge, GB;
Assignee:
National Research Development Corporation, London, GB;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
H01J / ;
U.S. Cl.
CPC ...
2503 / ; 250398 ;
Abstract
In an electron-beam probe instrument such as a scanning electron microscope in which the electron gun employs a field-emission cathode the condenser lens is of the `snorkel` design. The term `snorkel` is used to denote a single-pole magnetic lens in which the pole-piece has an axially extending nose portion. The lens is positioned so that the cathode region is immersed in the radial field at the nose of the lens. Preferably the lens is placed closely behind the cathode but outside the vacuum envelope.