Evaluation and discrimination method of "mura" in liquid crystal displays by just noticeable difference observation

Based on sensory analysis, quantitative evaluation method of the luminance non-uniformity, or "mura", of liquid crystal displays (LCDs) was investigated. We conducted a perception test by using pseudo mura and this approach led to "just noticeable differences" according to the various sizes of muras, intending to clarify the detection method and create an automated mura inspection process. The quality level of a mura can be described as a function between the mura area and the contrast, using the minimum perceivable contrast, or the "just noticeable difference" (JND) contrast, at that mura size. We developed the detection method by using a hardware system based on a commercially available CCD camera and a PC and ensured that the mura regions were distinguished from the background area even with the JND contrast. This paper describes the research in human perception and the approach to adapt the intrinsic rule of sensory analysis to the quantitative evaluation of mura.