Directional filter banks for detecting un-patterned TFT-LCD defect

The thin film transistor liquid crystal display (TFT-LCD) has become an actively used front of panel display technology with an increasing market. Intrinsically there is a region of non uniformity with low contrast that to human eye is perceived as a defect. Because the grey-level difference between the defect and the background is small, the conventional edge detection techniques are hardly applicable to detect these low contrast defects. Although several effort were dedicated in classifying the patterned TFT-LCD defects, only few researches were conducted on detecting the unpatterned TFT-LCD defects that accounts for approximately 15% of all defects produced during the manufacturing stages. This paper proposes a detection method for the un-patterned TFT-LCD defects by using the directional filter bank (DFB), Shen-Castan filter and maximum Feret's diameter. The effectiveness of the proposed method is tested through the experiment using real TFT-LCD panel images.