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Calibration method and apparatus

  • US 8,553,218 B2
  • Filed: 12/20/2010
  • Issued: 10/08/2013
  • Est. Priority Date: 12/28/2009
  • Status: Active Grant
First Claim
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1. A method of calibration of an optical inspection apparatus for inspecting a target, the optical inspection apparatus comprising at least one ingoing optical system for illuminating the target and at least one outgoing optical system for delivering radiation from the target to a detector, the method comprising:

  • using the ingoing optical system and the outgoing optical system in a first arrangement to obtain a first measurement of radiation in an outgoing direction, the measured radiation in the outgoing direction in the first arrangement being a combination of radiation illuminating a target from a first plurality of ingoing directions;

    using the ingoing optical system and the outgoing optical system in a second arrangement to obtain a second measurement of radiation in the outgoing direction, the measured radiation in the outgoing direction in the second arrangement being a different combination of radiation illuminating a target from a second plurality of ingoing directions; and

    using the first and second measurements and modeling a difference between the first and second arrangements to determine separately properties of the ingoing and outgoing optical systems.

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