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.

Abstract: First of all, this invention relates to a process based on the comparison of the image of a reference object I.sub.ref with the image of an object to be inspected I.sub.exa. Images I.sub.ref and I.sub.exa are picked-up, sampled, discretized and thresheld to produce electronic or binary images I.sub.REF and I.sub.EXA, respectively. These images are cleaned, then centered, I.sub.REF is adjusted to the minimum dimensional tolerances and becomes (I.sub.REF).sub.min. For each image point (pixel), the adjustment is performed by using a structuring element of variable size, the size of which is controlled by a bus from the data contained in a memory unit which take the location of the pixel on the reference object, into account. (I.sub.REF).sub.min is compared to I.sub.EXA which ensures the following function:[(I.sub.REF).sub.min OR I.sub.EXA ]EXCL. OR I.sub.EXA.The resulting image is the image of the "lack" type defects (which does not appear in I.sub.exa with respect to I.sub.ref).