| dc.description.abstract | In recent years, the TFT-LCD gradually becomes a mainstream of FPDs (Flat Panel Displays), and the request of image quality for a TFT-LCD becomes more and more severe. There are many items such as luminance, chromaticity, contrast, flicker, crosstalk and response time, etc. have to be evaluated for the image quality of display devices. But several of the other items have difficulties during evaluation of image quality, e.g. mura and image sticking. Mura is the most popular defect in producing TFT-LCD, in most cases, and is not easily identified so that those persons identifying mura in the industry need the experienced skill based on the related knowledge. It is thus obvious for manually identifying process by human beings to be costly and inconsistent. To overcome such hardship, an automated process for mura analysis has been considered.
In this study, we have investigated, analyzed and quantified the mura phenomena in the image quality of a TFT-LCD and hopefully try to set-up an optical evaluation system for mura. We found that the Cjnd (Just-Noticeable-Difference Contrast) value of the mura with abrupt boundary will be influenced by background luminance, mura size, and mura shape. As the background luminance increased, the Cjnd value decreased. However, when the background luminance was increased to above a threshold value around 172 cd/m2, there was no significant difference in Cjnd to human visual perception for a given mura size. Obviously, the relationship between Cjnd and background luminance was non-linear. Furthermore, the Cjnd value of mura with a smaller size was higher, and the Cjnd value of line type mura was higher than those of the other muras which with the same size but different shape. Besides, the threshold value for human visual perception of mura could be estimated with a graded mura. Comparing the results of Muras with abrupt boundary and graded ones, we also found that any type of mura detectable by human eyes could be estimated by the index of Just Noticeable Difference contrast.
Based on the analysis of our results, we modified the Cjnd equation which proposed by SEMI (Semiconductor Equipment and Materials International), and re-named as MCjnd which was more correlated to human visual inspection. Then, replacing the Cjnd with MCjnd, a new definition of mura level was obtained and called MSEMU, in contrast to SEMU proposed by SEMI. After comparing the analysis results of MSEMU and SEMU, it could be concluded that the MSEMU definition was reasonable and more correlated to human visual inspection for the mura analysis. | en_US |