Image quality inspection for electronic displays based on visual human factors

A novel image quality inspection method that uses the analysis of Fourier power spectrum is presented. The method can inspect mura(non-uniform) defects regardless of mura types. The original inspection image is transformed into frequency domain using Fourier transform. The Fourier power spectrum is filtered by CSF (Contrast Sensitivity Function) to match with the human visual perception. After the filtering, two kinds of histograms, frequency and direction, are calculated. The defect samples have large power spectrum values in the frequency histograms regardless their types. The direction histograms are effective to detect line mura, especially to detect the defective line angles. The validity of this method is shown by experiments.