Display Standard - Veritas et Visus

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Veritas et Visus Display Standard February 2009 SID Display Week 2008 Symposium May 20-23, Los Angeles, California In this third report of three, Phillip Hill covers the pick of the poster sessions with presentations from Toshiba Matsushita Display Technology, National Chiao Tung University, KDDI R&D Laboratories Inc./Tokai University, Korea University/ i-components, Otsuka Electronics, Industrial Technology Research Institute/ISUZU Optics Corp., Tatung University/Chunghwa Picture Tubes, Eldim, and the Center for Devices and Radiological Health/FIMI/Philips Relationship of Moving Edge Color Distortion and Response Spectrum Yoshi Enami, Otsuka Electronics, Shiga, Japan Moving edge color distortion is a phenomenon that is often seen in PDP TVs and other displays that use a phosphor and in displays using field sequential drive. By observation using a moving picture evaluation system using a color pursuit camera, which the company has developed, the company was able to confirm that moving edge color distortion also occurs in LCDs. In order to clarify the cause of moving edge color distortion in an LCD, the response of the LCD was measured using a high-speed spectrometer, and as a result, they were able to confirm that wavelength-dependence of retardation is a cause of moving edge color distortion. Pursuit images of respective types of displays taken by a moving picture evaluation system with a color pursuit camera (MPRT-2000CM) are shown in the photo. Images taken by this method are considered to be close to those perceived by the tracking vision of a human. Next, by determining cross sections in the moving picture movement direction of these images, the moving picture response curves in terms of the intensity measured by the CCD camera are obtained. By performing a matrix conversion, moving picture response curves of the R, G, and B pixels of a display can be determined. Measurements of the spectral response by a high-speed spectrometer showed that the wavelength dependence of the liquid crystal retardation is a cause of differences in the response speeds of the respective LCD display elements. Although the measurement method requires improvement, response measurement using the high-speed spectrometer enables simulation of the moving edge color distortion in the liquid crystal cell state, and the possibilities of simulation can be widened, for example, by adding information on the backlight, a simulation evaluation close to the final product state can be made. Presently, moving edge color distortion of LCDs is not discussed much. However it is considered that as further improvements are made in regard to moving edge blur, the influence of moving edge color distortion will become greater. In order to make improvements to moving edge color distortion, the respective display elements should be made uniform in response speed by making improvements to the wavelength dependence of the liquid crystal retardation, the company concludes. 46 Pursuit image of an LCD PC taken by the pursuit color camera system. The gray level is varied from black to white (0-255). The scrolling speed is 8 lines/frame and an XGA video signal is used.
Veritas et Visus Display Standard February 2009 New Multispectral Fourier Optics Viewing Angle Instrument for Full Characterization of LCDs Pierre Boher, Thierry Leroux, Thibault Bignon, and David Glinel; Eldim, Hérouville St Clair, France Fourier optics viewing angle instruments are now widely used to check the viewing angle behaviors of displays in terms of luminance, contrast and color. In the present paper Eldim introduces a new generation of EZContrast instruments that provides not only luminance and color at any incidence and azimuth angle but also the full spectral radiance in all the visible range. After a description of the new system they show that these new measurement capacities are useful in different situations: for LCD emissions, each color behavior can be understood in all its details and color variations measured with an unprecedented accuracy; for display components, their angular and spectral transmittance properties are useful for best understanding and more precise optical simulations. Standard color measurements, even if perfectly adjusted to the human eye sensitive, are quite restrictive compared to the complex spectral stimuli always emitted by any kind of display. A multispectral analysis with 20 to 30 channels in the visible range can be helpful. One example of multispectral measurement on an LCD is shown in the figure. In this example, the LCD has a CCFL backlight with a characteristic emission spectrum. The figure shows the multispectral measurement of the white state. The instrument provides the spectral radiance of the display at each incidence angle from 0 to88° and for all the azimuths. Some examples of spectra obtained along azimuth 0 are shown on the right part of the figure. From the spectral radiance it is possible to calculate the corresponding luminance and color coordinates with a better accuracy than with five color filters. Multispectral measurement on an LCD display in the white state: luminance in the Fourier plane (left) and some multispectral measurements for some incidence values along azimuth 0 (right). The company says that the instrument is simple to use and can replace spectrophotometers on goniometric stages in many situations with obvious advantages in particular in terms of speed. A polarization analysis option, in addition to spectral characterization, is also a very powerful tool in many applications. Study of the Ergonomics Requirement for Color Difference in Electronic Displays Yuzo Hisatake, Azusa Ikeda, Hideki Ito, Masaki Obi, Yasushi Kawata, and Akio Murayama Toshiba Matsushita Display Technology Co., Saitama, Japan The researchers have studied the dependency on color chroma and hue for allowable and optimal levels of color difference. The deeper the chroma, the wider the areas of optimal and allowable limits. The plot of each limit for deep RGB on the chromaticity diagram shows that the width for chroma is wider than that of hue area. ISO has published the standards of ergonomics requirements for FPDs (ISO-FDIS9241-300~307) in 2008). In these standards, the FPDs are required that the uniformity and viewing angle characteristics of the delta u’v’ value (color difference value) shall be less than 0.02 for all color chromaticity. However, Toshiba assumed that each limit is influenced by color chroma and hue. Thus, they studied ergonomics requirements of maximum color difference through subjective evaluation experiments using several pictures with high and low color chroma in six color hues (red, green, blue, cyan, yellow and magenta), three achromatic color (white, black and gray), and skin color displayed on a LCD monitor with a wide color gamut display. 47
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Display Standard - Veritas et Visus

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