Auto focus of a workpiece using two or more focus parameters

Optics: measuring and testing – Of light reflection

Reexamination Certificate

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Details

C356S499000, C356S521000

Reexamination Certificate

active

07948630

ABSTRACT:
Provided is a method for focusing a workpiece in the Z-axis for optical metrology. The auto focusing subsystem includes a focus detector having a tilt angle, a capture range, and a plurality of sensors. A processor coupled to the focus detector is configured to utilize the plurality of focus signals measured using the focus detector to determine two or more focus parameters. The two or more focus parameters and calibration data are used to determine an initial position of the workpiece and to generate instructions to move the workpiece to a best focus position.

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