78‐2: Measurement and Evaluation of Subpixel Brightness for Demura

Abstract

The luminance measurement accuracy of the demura system is a key factor that affects the performance of the demura. To objectively evaluate the performance of a demura system, we proposed a new evaluation method using white noise as test pattern. A test pattern was generated by adding a white noise to the gray level test pattern, the demura camera captures both the gray level pattern and the new pattern with the white noise. By calculating the subpixel brightness difference from the two captures, the subpixel brightness of this white noise pattern can be derived. The accuracy of the subpixel brightness measurement system can be evaluated with the autocorrelation of the derived subpixel brightness and the originally added random noise. The autocorrelation function characterizes both the effect of noise and spatial blur. If the display gamma is measured or known, the measured brightness can be converted to display digital counts and the root measure square error (RMSE) can be used as a metric for demura accuracy.