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System, a method and a computer program product for patch-based defect detection

  • US 9,235,885 B2
  • Filed: 01/31/2013
  • Issued: 01/12/2016
  • Est. Priority Date: 01/31/2013
  • Status: Active Grant
First Claim
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1. A computerized method for inspecting an article for defects based on processing of inspection images generated by collecting signals arriving from the article, the method comprising:

  • obtaining a candidate pixel of the inspection image, the candidate pixel being representative of a candidate article defect location;

    in a reference image, defining a source patch associated with a reference source pixel of the reference image which corresponds to the candidate pixel;

    in the reference image, based on the source patch and a predefined patch-similarity criterion, determining a similarity level with respect to each of a plurality of reference patches, each of which is associated with a reference image pixel;

    in the inspection image, rating each inspected pixel out of multiple inspected pixels with a representative score which is based on the similarity level of a reference patch associated with a reference pixel corresponding to the inspected pixel;

    in the inspection image, selecting multiple selected inspected pixels based on the representative scores of the multiple inspected pixels;

    determining a presence of a defect in the candidate pixel based on an inspected value of the candidate pixel and inspected values of the selected inspected pixels; and

    in each image of a plurality of images which includes the reference image;

    (a) defining multiple source patches of different shapes, wherein each of the multiple source patches is associated with a reference source pixel of the image; and

    (b) for each of the source patches of the image;

    based on the source patch and a respective patch-similarity criterion, determining a similarity level with respect to each of a plurality of reference patches, each of which is associated with a pixel of the image;

    thereby for each of a plurality of pixels of the image, determining a plurality of similarity levels that are determined for multiple reference patches of different shapes which are associated with the respective pixel of the image;

    wherein the rating comprises rating each inspected pixel out of at least one of the multiple inspected pixels with a representative score which is based on multiple similarity levels of reference patches associated with pixels of the plurality of images which correspond to the inspected pixel.

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