Image analysis – Histogram processing – For setting a threshold
Patent
1983-05-12
1985-07-30
Boudreau, Leo H.
Image analysis
Histogram processing
For setting a threshold
356237, 358101, 358106, G06K 900
Patent
active
045326509
ABSTRACT:
Defect detection apparatus including a mechanical and optical system for scanning duplicate areas of a photomask to be inspected, electronic means for converting the optically scanned information to digitized form, memory for storing such information, and means for comparing information obtained from one inspected area to the other inspected area to determine differences therebetween, such differences being classified as defects. The detection is accomplished using a vector gradient within a matrix technique to develop candidate and cancellor information which is then logically manipulated to qualify the data obtained from each pixel matrix and then, after qualification, is used to determine whether or not a defect has been detected. The subject invention has particular application to the detection of defects occurring at pattern corners within the inspected photomask and is specifically directed to overcoming difficulties previously encountered in detecting such defects.
REFERENCES:
patent: 4148065 (1979-04-01), Nakagawa et al.
patent: 4282510 (1981-08-01), Southgate
patent: 4282511 (1981-08-01), Southgate et al.
patent: 4403294 (1983-09-01), Hamada et al.
patent: 4454542 (1984-06-01), Miyazawa
patent: 4472738 (1984-09-01), Hada et al.
Wihl Mark J.
Wihl Tim S.
Boudreau Leo H.
Hamrick Claude A. S.
KLA Instruments Corporation
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