Image analysis – Histogram processing – For setting a threshold
Patent
1984-12-20
1987-06-09
Boudreau, Leo H.
Image analysis
Histogram processing
For setting a threshold
382 45, 358101, 356401, G06K 900
Patent
active
046726764
ABSTRACT:
A method and apparatus for aligning a ceramic substrate provided with two small alignment crosses formed at the same time as the metallic pattern and located on both sides of a symmetry axis, said substrate being disposed on an alignment platen. The method includes the steps of generating in two insepection windows, comprised each of a matrix of photodiodes divided into quadrants i (i=1, 2, 3, 4), a reference image of the same dimensions as the image of each cross, and determining, for each quadrant and for each cross, "exposed" areas (S.sub.i.sup.+, S.sub.i.sup.+ ') corresponding to those portions of the image of the cross which extend beyond the outline of the reference image, and "masked" areas (S.sub.i.sup.-, S.sub.i.sup.- ') corresponding to those portions of the reference image which extend beyond the outline of the image of the cross. The values of said areas are used to compute the corrections (.DELTA.x, .DELTA.y; .DELTA.x', .DELTA.y') required to cause the center of a cross to coincide with its ideal position in the center of the corresponding inspection window. The final corrections (.DELTA.X,.DELTA.Y,.DELTA..theta.) required to adjust the alignment platen are defined as: ##EQU1## (where is the distance between the two crosses and also between the centers of the inspection windows). The advantage of this method is that it deals with areas and therefore minimizes the adverse effects of the irregularities of the crosses that are inherent in the metallization process.
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Boudreau Leo H.
Couso Jose L.
Crane John D.
International Business Machines Corp.
Sandt Robert E.
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