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Measurement method and apparatus for alignment

  • US 4,641,257 A
  • Filed: 07/02/1984
  • Issued: 02/03/1987
  • Est. Priority Date: 07/07/1983
  • Status: Expired due to Term
First Claim
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1. A measurement apparatus, comprising:

  • detecting means for detecting a mark on each of a plurality of objects and for producing a signal having a peak value in response to the detection of each of the marks, so as to form a series of signals;

    peak detecting means for detecting the peak values of the signals;

    means for determining a slice level for each of the peak values detected by said peak detecting means; and

    means for sequentially comparing the signals with their respective slive levels, as determined by said slice level determining means, and for determining an interval between the marks on the basis of the comparison.

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