In this paper, we propose the use of Laplacian of Gaussian (LOG) filters in the detection of Cluster Mura defects and Vertical-Band Mura defects on Liquid Crystal Displays. To detect Cluster Mura defects, 2-D LOG filters with their shapes matching the shapes of Cluster Mura are adopted. The optimal threshold for the detection of Cluster Mura is determined based on the SEMU formula. On the other hand, to detect Vertical-Band Mura, a 1-D LOG filter is used over the projected 1-D intensity profile to check if the variation tendency of the intensity profile is changed. The portions with inconsistently intensity variation are regarded as the portions where V-Band Muras occur. The simulation results demonstrate the LOG filters are very useful in the detection of Mura defects.

In this paper, we propose an automatic inspection system, which can automatically detect four types of muras on an LCD panel: cluster mura, v-band mura, rubbing mura, and light leakage mura. To detect cluster muras, the Laplacian of Gaussian (LOG) filter is used. A multi-resolution approach is proposed to detect cluster muras of different scales. To speed up the processing speed, this multi-resolution approach is actually implemented in the frequency domain. To detect v-band muras, we check the variation tendency of the projected 1-D intensity profile. Then, v-band muras are detected by identifying these portions of the 1-D profile where a large deviation occurs. To detect rubbing muras, we designed a frequency mask to detect distinct components in the frequency domain. To detect light leak muras, we apply image mirroring over the boundary parts and adopt the same LOG filter that has been used in detecting cluster muras. All four types of mura detection are integrated together in an efficient way and simulation results demonstrate that this system is indeed very helpful in detecting mura defects.