Ryoji Yoshitake

Trends in Usability Research and Activities in Japan

This article presents an outline of information on the usability activities in Japan with a focus on the last 10 years. Although there were many activities in academia, substantial efforts were made in industry, and both activities coincided to form unique usability engineering in the country. Because of the language barrier that exists in many Japanese usability engineering professionals, just a few works have been presented at international conferences. This is the reason why the tried to summarize in English the usability engineering activity in Japan.

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.

Specular and diffuse reflection measurement feasibility study of ISO9241 Part 7 method

Abstract ISO DIS9241 Part 7 describes the requirements of display reflection for CRTs and some flat panels (emissive displays whose colour and luminance contrast do not vary strongly as a function of the viewing direction). The Japanese member body of ISO TC159 SC4 has been contributing to the Part 7 measurements (Kubota, Journal of Light and Visual Environment 21(1) (1997) 33–42). In 1996, some issues of the reflection measurement were pointed out at the ISO TC159 WG2 meeting (Yoshitake et al., N369, 1996) and SID conference (Jones et al., SID 96 Digest, 1996, pp. 203–206). The issues are the uncertainty of the evaluation method. It is reported to what degree the issues affect the Part 7 measurement requirement, showing the results of actual experiments for CRTs and LCDs. The goal is to verify that the ISO DIS9241 Part 7 method has an effective certainty from an ergonomic point of view.

P‐178L: Late‐News Poster: The Number of Sub‐Pixel Defects that is Acceptable for Various Panel Size and Pixel Sizes

Users patience limit of pixel defects from each panel size and pixel size should differ. We investigated the influence of these parameters to the limit by subjectivity evaluation in the design viewing distance for each application. As results, the number decreased, so that panel size or pixel size were small.