Defect detection in inhomogeneous textures using 3D Fourier reconstruction

• Main Authors: Chih-Chia Kuo, 郭志嘉
• Other Authors: 蔡篤銘
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/58498082057614238320

碩士 === 元智大學 === 工業工程與管理學系 === 90 === The purpose of this research aims at the use of machine vision for automatic inspection of defects in inhomogeneous textures such as the sputtered glass substrates of touch panels. The proposed method does not rely on local features of textures. It is based on a global image reconstruction scheme using the 3D Fourier transform. Since a single inhomogeneous texture image does not show homogeneity everywhere in its 2D image, we use a sequence of faultless 2D images to construct a 3D image (the original 2D x-y plane and the additional time-axis) so that the homogeneity of textures can be observed from its time frame. The method of surface defect inspection is carried out by the 3D Fourier transform of the 3D image and the reconstruction technique of the 3D inverse Fourier transform. By finding an adequate radius in the 3D power spectrum space, and setting the frequency components outside the selected cylinder to zero, we can remove the periodic, repetitive patterns of textures in the time axis. In the reconstructed image, the inhomogeneous region in the original image will have an approximately uniform gray level, and yet the defective region will be distinctly preserved. Experiments on glass substrates in the sputtering process have shown that if each 2D reference image has homogeneity character in its time frame, then our proposed method will have promising results for detecting defects in inhomogeneous textures.