Automated surface inspection for directional textures

摘要

In this paper we present a global approach for the automatic inspection of defects in directionally textured surfaces which arise in textile fabrics and machined surfaces. The proposed method does not rely on local features of textures. It is based on a global image restoration scheme using the Fourier transform. The line patterns of any directional textures in the spatial domain image are removed by detecting the high-energy frequency components in the Fourier domain image using a one-dimensional (1D) Hough transform, setting them to zero, and finally back-transforming to a spatial domain image. In the restored image, the homogeneous line region in the original image will have an approximately uniform gray level, whereas the defective region will be distinctly preserved. A statistical process control scheme is therefore used to set up the control limits for discriminating between defects and homogeneous line patterns. The experiments on a variety of textile fabrics, machined surfaces and natural wood have shown the effectiveness of the proposed method.