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:
Jul. 15, 1986
Filed:
Oct. 28, 1983
J Evan Grund, San Jose, CA (US);
Nanometrics Incorporated, Sunnyvale, CA (US);
Abstract
A method for the automatic fine focusing of an image scanning densitometer, micrometer, or television camera or the like, after an initial manual focus has been made on the edge of a discernible feature on the surface of an object of interest. A plurality of at least three, and preferably five, scans are made across the image of the feature at a corresponding plurality of focus positions, and the variations in light intensities are noted at each of a plurality of locations in each scan so that an edge value may be determined for each focus position. If plotted, edge values as a function of focus position appears as a second order curve of the form, edge value=ae.sup.2 +be+c, from which the values of the coefficients 'a' and 'b' may be determined by the least squares best fit method. When the derivative of the curve equation is made equal to zero to correspond to a zero slope or bottom of the curve, the best focus position is readily determined to that the precise focus may be adjusted to that position.