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Guardbands for pattern inspector

  • US 5,001,764 A
  • Filed: 03/25/1988
  • Issued: 03/19/1991
  • Est. Priority Date: 03/25/1988
  • Status: Expired due to Term
First Claim
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1. A computerized method of reducing the incident of false error reporting for an optical pattern inspection system, comprising the steps of:

  • identifying the pattern boundaries of a database representation of an ideal pattern, wherein the ideal pattern is comprised of one or more reference polygons, and the data description of each reference polygon is contained within a frame of data, and each side of a polygon is a line segment completely contained within a single frame;

    constructing data representations of guardbands around said boundaries and constructing a guardband polygon surrounding each line segment of each side of each reference polygon, wherein each guardband polygon is completely contained within the frame of data containing the polygon whose side it surrounds;

    constructing a dummy reference polygon in a frame adjacent to a frame having a side of an actual reference polygon a distance less than epsilon away from the common frame boundary of the two adjacent frames;

    constructing a guardband around the dummy reference polygon a distance at least as great as epsilon from the side of the actual reference polygon which is a distance less that epsilon away from the common frame boundary;

    comparing data generated from an optically detected pattern on a target with the database representations of the ideal pattern, to detect miscompares; and

    identifying as errors only those miscompares which do not occur within the guardbands.

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