Automatic evaluation of defect severity by shape and size

Two experimental devices for the classification and measurement of surface defects, using photoelectric detectors (banks of photo-cells or flying spot scanner) are described which have been applied to the automatic inspection of tubes. The first system, which was developed to cover a particular inspection specification, has defect length as the only criterion. In the second system, defect length, width, and to some degree depth is taken into consideration. A technique of homing and defect following is employed, which ignores neighbouring irrelevancies that otherwise falsify the pattern evaluation. Variations of the second system could be applied to other visual inspection problems. The technique generally is not restricted to optical transducers, but could be applied to eddy currents, and ultrasonics, where a scanning system is incorporated.