Method for focusing of disk-shaped objects with patterned surfaces during imaging

US6696679B1 · kind B1 · utility

Assignee

• Leica Microsystems Wetzlar GmbH · DE

Inventors

• Michael A. Graef · Gräfelfing, DE
• Uwe Graf · Solms, DE
• Joachim Wienecke · Jena, DE
• Guenter Hoffmann · Chicago, US
• Karl-Heinz Franke · Ilmenau, DE
• Lutz Jakob · Jena, DE

Key dates

• Filing date: Apr 12, 2000
• Grant date: Feb 24, 2004
• Expiry date: Apr 12, 2020

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N21/9506
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A method for focusing on disk-shaped objects with patterned and unpatterned surfaces includes imaging of the patterned and unpatterned surfaces on a disk-shaped object for defect detection and defect classification by using various preset values of a focus regulation system to acquire the image sequence. At least one preset value is learned on the basis of an image sequence at least at one position in a substantially flat reference region of the surface of the disk-shaped object. A regulated adjustment is provided of a measurable distance from a carrier plane to a reference plane, wherein the carrier plane serves as a support for the disk-shaped objects. The distance is adjusted by applying the at least one preset value, which is overlaid on the regulation system, a focus state is evaluated by an image processor according to at least one rule, and the at least one preset value is ascertained therefrom.