Application of the Haar wavelet to mura detection for polarizer

“Mura” is a local lightness variation without a clear contour on a uniform surface image, which imparts an unpleasant sensation to human vision. There exist three common types of mura including line mura, band mura, and area mura. In this study, the Haar wavelet transform method is applied to detect muras on the polarizer. Because of its capability of multi-resolution analysis for digital images, different sized muras at different locations can be segmented. Since the Haar wavelet transform cannot extract all high frequency components from an image at one time, the original image is decomposed into a main image and a sub-image at the beginning. Then the wavelet transform technique is implemented to extract all high frequency components from these two images. Experiments were extensively conducted on different frequencies and sizes of muras. Experimental results show that the presented approach is able to detect all line muras, as well as most band and area muras.