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:
Nov. 26, 2002
Filed:
Oct. 07, 1999
Andreas N. Dorsel, Menlo Park, CA (US);
Kenneth L. Staton, San Carlos, CA (US);
Cassandra Dey, Palo Alto, CA (US);
George P. Tsai, San Jose, CA (US);
Agilent Technologies, Inc., Palo Alto, CA (US);
Abstract
A laser generates a collimated laser beam which passes through a lens off-axis. The beam is focused at a focal plane on a substrate surface. A first position sensitive detector receives the laser beam reflected from the substrate surface through the lens to generate a first signal proportional to lateral beam offset. A beam splitter may be provided to direct a portion of the laser beam before passing through the lens toward a second position sensitive detector to generate a second signal proportional to laser beam pointing instability. Apparatus computes the difference between the first and second signals, the difference being a defocused error signal. It is preferred that the first position sensitive detector be located at a distance from the lens that is at least twice the lens focal length.