Process for inspecting and automatically sorting objects showing patterns with constant dimensional tolerances and apparatus for carrying out said process

摘要

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 Iref with the image of an object to be inspected Iexa. Images Iref and Iexa 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 IREF and IEXA to be carried out. The image processing includes the following operations: First of all constructing electronic images IREF max and IREF min respectively which are images IREF 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: [IREF max OR IEXA] EXC.OR IREF max and [IREF min OR IEXA] EXC.OR IEXA. 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.