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. 05, 1991
Filed:
Sep. 28, 1989
Setsuo Norioka, Tokyo, JP;
JEOL Ltd., Tokyo, JP;
Abstract
In a field emission gun, current intensity of the electron beam passing through the gun anode contains a fluctuation component due to the ion bombardment and ion absorption near the emitter tip. For this reason, a scanning electron microscope having a field emission gun usually incorporates a fluctuation compensation device, which generates the signal ratio of the secondary electron signal from a specimen irradiated by the electron beam and the monitor signal corresponding to the current intensity of the electron beam passing through the gun anode and supplies the signal ratio for brightness modulation signal to the scanning image display means of the microscope. However, if the electron beam intensity is varied in a very wide operating range, the conventional fluctuation compensation device cannot operate with enough compensation effect. In this invention, the signal level of the monitor signal is maintained constant, so that the fluctuation correction device operates with enough compensation effect for a wide operating range of electron beam intensity.