A new approach for image processing in foreign fiber detection

In the textile industry, different types of foreign fibers may be mixed in cotton that need to be sorted out to ensure the quality of the final cotton textile products. Automated visual inspection (AVI) system is a popular tool at present for real time foreign fibers detection in lint. The image processing is one of the key techniques in the AVI system. This paper presents a new approach for processing images of foreign fibers. This approach includes four main steps, namely, image transformation, image enhancement, image segmentation and segmentation post-processing. In the first step, color images were captured and then transformed into gray-scale images. In the second step, the histograms of the gray-scale images were analyzed, and a piecewise nonlinear transform model was proposed to enhance the image based on the analysis results. Thirdly, an improved Otsu's method was employed for segmenting the gray images of foreign fibers. Finally, post-processing of segmentation was performed, and a modified closing operation in mathematics morphology was proposed to fill up the image gaps of the wirelike foreign fibers caused by segmentation, and an area threshold method was suggested to remove the small objects generated by pseudo-foreign-fibers. The results indicate that the contrast between objects and background can be remarkably improved by the proposed enhancement model. The Otsu's method can effectively subdivide the enhanced images into objects and background. The gaps can be filled up by the modified closing operation, and the small objects can be removed effectively using the Area Threshold algorithm.