9 research outputs found
Pinhole Detection in Slab Images using Image-processing
No full textMasterIn this paper, we introduce an image-processing algorithm that detects pinholes in steel slabs. Because the pinhole is relatively small and similar to noise components, it is difficult to distinguish pinhole from a steel slab surface. To increase detection accuracy, we propose a new algorithm for pinhole detection. We applied Gabor filters to extract defect candidates and subsequently developed a mask to score the specific features of each pinholes. The performance of the proposed algorithm was evaluated on 1764 subimages116 of these images had pinholes, and the rest of the images were free of defects. The proposed algorithm has 87.1% accuracy for the detection of pinhole images and false alarm is 3.8%
A new Gabor filter combination and its application to fine defects detection is steel surfaces
No full textDoctorIn this thesis, a new Gabor filter combination for detecting various sizes of defects, and its application to fine defects detection in steel surfaces. To detect various sizes of defects, two filters were effective than a single filter.
First, a new Gabor filter combination method was proposed. Response is obtained by linear combination of two Gabor-filtered images. Coefficient of linear combination is determined by energies of two Gabor-filtered images. The performance of proposed method was tested through the comparison with filter addition and filter selection.
Second, an algorithm for detecting seam cracks using Gabor filter combination was proposed. Seam cracks are narrow cracks generated in the edge regions of steel plates. Because the widths of seam cracks are various, we applied the Gabor filter combination method. To increase the performance, Gray value intensity transformation in pre-processing, and region of interest selection in post-processing, were proposed. New features were designed to increase the performance of classification. The proposed algorithm was tested on the images obtained in real production line.
Third, an algorithm for detecting pinholes was proposed. Pinholes are very tiny holes generated in the surfaces of scarfed slabs. To detect various sizes of pinholes, the Gabor filter combination was applied. A new image segmentation method was proposed in pre-processing. To reduce the number of pseudo-defects, dual thresholding method was used. We have increased the performance of classification by adding new morphological features to general texture based features. To evaluate the performance of proposed algorithm, an images obtained in real production line were used
