Yumi Mori

Quantitative evaluation of “mura” in liquid crystal displays

The visual performance of liquid crystal displays (LCDs) has usually been evaluated by visual inspection during the manufacturing process. One of the visual problems hardest to recognize are regions of low contrast and nonuniform brightness called mura. The accurate and consistent detection of the mura is extremely difficult because there are various shapes and sizes of mura and the inspection results tend to depend on the operators. We conducted a study on the quantitative evaluation of mura based on visual analysis, intending to clarify the de- tection method and create an automated mura inspection process. We developed an algorithm and a hardware system based on a commer- cially available charge-coupled-device camera and a personal computer system with an image processor board. This system can successfully identify and evaluate mura. The algorithm was developed from research on visual analysis and human perception. We converted the front-of- screen images from the LCDs into distributions of luminance information, and the mura regions were distinguished from the background area us- ing our novel algorithm. Our identification method can also distinguish between the muras caused by flaws in the LCD cells and the intentionally designed nonuniform luminance distribution of the backlight.

Multilevel parallelization on the cell/B.E. for a motion JPEG 2000 encoding server

The Cell Broadband Engine (Cell/B.E.) is a novel multi-core microprocessor designed to provide high-performance processing capabilities for a wide range of applications. In this paper, we describe the worlds first JPEG 2000 and Motion JPEG 2000 encoder on Cell/B.E. Novel parallelization techniques for a Motion JPEG 2000 encoder that unleash the performance of the Cell/B.E. are proposed. Our Motion JPEG 2000 encoder consists of multiple video frame encoding servers on a cluster system for high-level parallelization. Each video frame encoding server runs on a heterogeneous multi-core Cell/B.E. processor, and utilizes its 8 Synergistic Processor Elements (SPEs) for low-level parallelization of the time consuming parts of the JPEG 2000 encoding process, such as the wavelet transform, the bit modeling, and the arithmetic coding. The effectiveness of high-level parallelization by the cluster system is also described, not only for the parallel encoding, but also for scalable performance improvement for real-time encoding and future enhancements. We developed all of the code from scratch for effective multilevel parallelization. Our results show that the Cell/B.E. is extremely efficient for this workload compared with commercially available processors, and thus we conclude that the Cell/B.E. is quite suitable for encoding next generation large pixel formats, such as 4K/2K-Digital Cinema.

Extraction and evaluation of mura in liquid crystal displays

The visual performance of liquid crystal displays (LCDs) has been usually inspected and evaluated by sensory analysis at the manufacturing process. One of the most indistinct visual problems is low-contrast non-uniform brightness region called muras. The accurate and consistent detection of the muras is extremely difficult because there are various shapes and sizes of muras and the inspection results tend to depend on the operators. We conducted a study on the quantitative evaluation of muras based on visual analysis and human perception. We converted the front of screen (FOS) images from the LCDs into distributions of luminance information, and the mura regions were distinguished from the background area using our novel algorithm. This approach also led to a weighting function for the categories of muras that appear in the panels. Our identification method can also distinguish between the muras caused by flaws in the LCD cells and the intentionally designed non- uniform luminance distribution of the backlight.

Cell-Broadband-Engine-Based Realtime Wavelet Decomposition for HDTV Video Images and Beyond

The cell broadband engine (CBE) is a novel multi-core microprocessor designed to provide compact and high-performance processing capabilities for a wide range of applications. Real-time image processing applications with parallelism for large amounts of data are good examples to demonstrate the unique capabilities of the CBE. In this paper, we describe the evaluation of the performance for image processing using wavelet transforms on CBE. Our results show that the CBE is extremely efficient in this processing compared with commercially available processors, and thus, we conclude that the CBE is quite suitable for next generation large pixel formats, such as 4K/2K-digital cinema

Measurement method for low-contrast nonuniformity in liquid crystal displays by using multi-wavelet analysis

One of the visual problems hardest to recognize in liquid crystal displays (LCDs) is an area of non-uniform brightness called a mura. The accurate and consistent detection of a low-contrast mura is extremely difficult because the boundary between the regional mura and the background is indistinct. This paper presents a novel method for detection and quantitative measurement of low-contrast mura. Compared with some wavelet approaches, the multiple resolution analysis method based on the Symmetric Selesnick multiwavelet has advantages for practical use.