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. 06, 2001
Filed:
Nov. 19, 1998
Alexander Henstra, Eindhoven, NL;
Marcellinus P. C. M. Krijn, Eindhoven, NL;
Philips Electron Optics B.V., Eindhoven, NL;
Abstract
Electron-optical rotationally symmetrical lenses inevitably suffer from chromatic aberration which often determines the resolution limit at low acceleration voltages. This lens defect cannot be eliminated by compensation by means of rotationally symmetrical fields. In order to improve the resolution nevertheless, it has already been proposed to correct the chromatic aberration by means of a corrector (,) provided with two correction elements (,). Each correction element consists of a number of quadrupole fields. Using the known corrector, it has been found that the chromatic magnification error is inadmissibly high. In order to solve this problem, the correction elements in the corrector according to the invention are provided with at least five layers of electrodes (,-,-,-,-,) which produce quadrupole fields. Because of the strong periodicity of the electron paths in the correcting quadrupole fields, the chromatic magnification error is limited sufficiently (or even reduced to zero) so as to allow the use of the corrector for practical purposes.