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

Abstract

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.

Flexoelectric Effect on Image Sticking Caused by Residual Direct Current Voltage and Flicker Phenomenon in Fringe-Field Switching Mode Liquid Crystal Display

“…As mentioned above, when the transmittance of gray level changes due to the DC offset voltage, how much DC offset is generated, and does the image sticking problem occur? We focused on the JND (just noticeable difference) of brightness to calculate the acceptable DC offset voltages when image sticking occurs at each gray level [9]. The JND of brightness based on the GSDF (Grayscale Standard of Display Function) of DICOM (Digital Imaging and Communications in Medicine) standard, which is the medical monitor standard, is shown in Fig.…”

Mura‐type effect on human‐vision inspection

“…Experiments were modified based on SEMI and Mori's experiment. 11,12 In the current study, JNDs of the human eyes were measured by the psychophysics method of 2AFC (two alternatives, forced-choice) to prevent a large judging difference among subjects and using QUEST 7 to shorten the experimental time. The visual contrast threshold of each pattern would be obtained, depending on the subject's response to the changed pattern contrast.…”

Investigation of oil‐motion non‐uniformity in a reflective display based on electrowetting

“…10 Mura phenomenon always exists in the LCDs because of contamination of the TFT array during manufacturing. 11 Defective pixels could possibly reduce the display quality, and the defect visibility is an important factor in evaluating these technologies. In the published literature, defects in printed paper, especially halftone banding, have been widely evaluated.…”