Detection of spot-type defects on liquid crystal display modules

In the manufacturing process of a LCM(Liquid Crystal Display Module), many spot-type defects can be occurred on the surface of LCM due to various physical factors. The existence and pattern of such defects are very important in determining whether the LCM is normal or not. To enhance the accuracy and reproducibility of LCD inspection, this paper introduces an automated inspection method using a computer vision technique. The LCM defects are classified into macro-defects and micro-defects. One is detected by using a macro-view area camera and the other by using six micro-view line cameras. An adaptive multilevel thresholding method using statistical characteristics of local block is proposed for a macro-view image while the detection method for a micro-view images composed of R, G, B sub-cells involves a pattern elimination technique using the pixel difference and adaptive multilevel thresholding. The proposed inspection system is tested using many real LCMs having different defects, and the resulting performance confirms the effectiveness of the proposed algorithm.