Quantitative Evaluation of Luminance Nonuniformity "Mura" in LCDs Based on Just Noticeable Difference (JND) Contrast at Various Background Luminances

Tohru TAMURA
Toshifumi SATOH
Takayuki UCHIDA
Takashi FURUHATA

Publication
IEICE TRANSACTIONS on Electronics   Vol.E89-C    No.10    pp.1435-1440
Publication Date: 2006/10/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e89-c.10.1435
Print ISSN: 0916-8516
Type of Manuscript: Special Section INVITED PAPER (Special Section on Electronic Displays)
Category: 
Keyword: 
image quality,  LCD,  luminance,  nonuniformity,  JND contrast,  

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Summary: 
An analytical approach using human perception has been applied to the evaluation of the front-of-screen (FOS) quality of liquid crystal displays (LCDs), particularly regarding the regions of luminance nonuniformity called "muras." The accurate and consistent inspection of muras is extremely difficult because muras have various shapes and sizes as well as contrasts. And inspection results tend to depend on inspectors during the LCD manufacturing process. To determine the quantitative scale that shows the evaluation results of mura matching human perceptions, first, we conducted a perception test and clarified the "just noticeable difference" (JND) contrast according to the type of mura. Second, the relationship between the JND contrast of mura and background luminance was investigated. Finally, we proposed a quantitative scale of mura level on the basis of the JND contrasts at various background luminances. In this paper, we describe our research on human perception of muras at various background luminances and an approach to determining the quantitative scale of visible muras.