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Automatic wafer alignment technique

  • US 4,475,122 A
  • Filed: 11/09/1981
  • Issued: 10/02/1984
  • Est. Priority Date: 11/09/1981
  • Status: Expired due to Term
First Claim
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1. A method for use in a system in which a video camera is used to view a target of expected characteristics, said method being used for ascertaining whether a feature evident in the video image corresponds to the actual target, said video camera providing output data consisting of an average intensity value for each scan line or column of said video image, comprising:

  • ascertaining, from said video data, each feature edge evident in the video display,sequentially correlating the data for each ascertained edge with the data for each other ascertained edge to determine all pairs of edges which represent potential targets, andselecting the best target by weighted comparison of selected parameters of all determined pairs of edges.

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