The following figure shows the influence of the area criterion used to select only the significant defects. It appears clearly that if we try to detect very small objects, noise is detected also, that is why the number of detected defects is too high compared to the number given by the expert. This is a first step, as it is now necessary to check that the detected objects are actual defects, in order to evaluate the false detection rate. The next figure illustrates the comparison of the parameter, as computed by the software or the expert. As expected, when too many porosities are detected by the software, the ratio obtained is also to important, as the area of porosities is bigger.
Some cases are however interesting to discuss on.
The comparison of the maximal diameter shows that the image processing developed for big porosities is quite efficient. Indeed, the size of big porosities is estimated correctly, as the mean error is 120 m, which is close to the pixel size. Moreover, the diameter is either over or under estimated, which indicates that the software does not systematically grow the defects. It is either adapted to radioscopic images or digitized films, and is able to classify the weld according to a given standard. Radioscopy can thus provide a first and very quick inspection result, allowing a first sorting of the welds, as lacks of penetration are prohibitive defects.