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Mura defects in LCM panel of TFT-LCD have the properties of local low contrast and luminance variation without a clear contour on a uniformly produced surface. This research proposes two methods which are discrete cosine transform (DCT) and discrete wavelet transform (DWT). These methods successfully detect simulated blob-mura and real mura defects. DWT method is based on symmetrical 9/7 tap Daubechies coefficients that is superior for filtering the regular structure of color filter and small area defects. DCT method is better for detecting luminance variation in large area and poor for small ones.
Chen et al. (2008) studied this question.