Importance

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Abstract

This invention relates to a process for inspecting and sorting objects showing patterns with constant dimensional tolerances as masks, integrated circuit chips, modules currently in use in the electronic industry. The process is 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 after being picked up and sampled, are thresheld to produce binary electronic images which are cleaned, then centered to allow the comparison of resulting electronic images I.sub.REF and I.sub.EXA to be carried out. The image processing includes the following operations: First of all constructing electronic images I.sub.REF max and I.sub.REF min respectively which are images I.sub.REF expanded and eroded by a structuring element adapted to the dimensional tolerances of the object to be inspected. Then, the images of the defects of the 'spreading' type and of the 'lack' type are constructed by respectively carrying out the following logic operations: [I.sub.REF max OR I.sub.EXA ] EXC.OR I.sub.REF max and [I.sub.REF min OR I.sub.EXA ] EXC.OR I.sub.EXA. Then, the defect images are analyzed with respect to a predetermined reject criterion. At last, final sorting step is carried out. This invention also relates to an apparatus for carrying out said process. Said apparatus can comprise a digital computer for automatizing the various steps which are indicated above.

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First Claim