Human vision based detection of non-uniform brightness on LCD panels

We propose a method to detect defects due to spatially non-uniform brightness on LCD panels by using a machine vision technique. The detection method is based on human vision so that proper subjective assessment experiments were conducted to investigate the correlation between the parameters related to non-uniformity and the degree how easily observable it is. The visibility of the defects reveals to depend mainly on the spatial gradient of brightness variation. Thus, in the proposed method, the spatial gradient that is calculated by using extracted contours will be utilized to detect the defects due to non-uniform brightness. The detection method comprises four parts: contour extraction, spatial gradient calculation, decision of defects, and display of defects. We applied the method to the images captured from practical LCD panels with non-uniformity defects and the results were consistent with detection by a human inspector.