Weld Slim Line Defects Extraction Based on Adaptive Local Threshold and Modified Hough Transform

Computer aided evaluation is objective, scientific and standardized, and automatic defects detection technology based on X-ray digitized images is the core of computer aided evaluation. However, for the slim line defect whose average width is not more than three pixels, such as some weak incomplete penetrations, cracks and so on, its contrast to background is extremely low, and normal X-ray defects detection algorithm can not detect it effectively. This paper proposes a special defect segmentation algorithm to detect this kind of defects. Firstly adaptive local threshold is performed column by column to extract slim line defects preliminarily, and then the improved Hough transform is utilized to eliminate the noise, and segment the line defects. Corresponding experimental results show that the proposed algorithm is effective to detect low-contrast slim line defects in X-ray digitized images of different grey ranges.