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:
Jan. 28, 1986
Filed:
Jun. 16, 1983
Kenneth C Smith, Cambridge, GB;
Stephen J Erasmus, Mountain View, CA (US);
National Research Development Corporation, London, GB;
Abstract
An electron beam instrument having an objective lens coil 14 and stigmator coils 18 has its astigmatism corrected for by measurement of the contrast in the final image. The currents through the objective lens and the stigmator coils are adjusted in sequence iteratively to optimize the contrast. The optimum contrast may be either a maximum contrast or a minimum contrast depending on the nature of the instrument and its mode of operation. Measurement of contrast may be made by measuring the magnitudes of successive points of an image and calculating the variance. Alternatively two measurements of magnitude at each point of an image may be made and the covariance calculated.