PURPOSE: To enable defect extraction with the same criterion regardless of growing intricacy of the kind of specimen pattern shapes, by defining a boundary portion of a local pattern as a zone of immunity and checking the local pattern, for existence inside a reference pattern displacement allowable range.
CONSTITUTION: An image signal from an image pick-up apparatus 1 is binarized with a binarization circuit 2 and an immunity range is segregated with immunity setting circuits 3, 4. Next, local patterns are cut out from outputs of the circuits 2 and 3 with local pattern extraction circuits 5, 6, 7. And a design pattern memory 8 which has already memorized design patterns introduces the design pattern subject to image pick-up to a local pattern segregating circuit 9 in synchronization with the scanning operation of the apparatus 1. Next, by the local patterns segregated by the circuits 5, 6, 7, 9, through a defect extraction circuit 10, if, between the local patterns and a plurality of local patterns obtained from the reference, only a single combination devoid of disagreement does happen to exist, a decision is given as flawless and if the condition is on the contrary, then the decision is given as defective and thus, a defect of the pattern is extracted.
OKAMOTO KEIICHI
NOMOTO MINEO
Next Patent: BORED HOLE INSPECTION