Display Standard - Veritas et Visus

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Veritas et Visus Display Standard February 2009 Novel Evaluation Method for Visibility of Reflective Electronic Paper Display by Comparative Examination with Liquid Crystal Display; Kohsuke Nishimura, KDDI R&D Laboratories Inc., Saitama, Japan Makoto Omodani, and Junko Imai, Tokai University, Kanagawa, Japan An organoleptic examination technique is proposed for evaluating visibility of reflective electronic paper displays (EPs). The visibility of EP was compared with that of LCD under various ambient illuminances. The threshold illuminance, above which the visibility of EP was better than that of LCD, was successfully extracted. A reflective EP is much less power-consuming than a transmissive or an emissive display as far as for showing still images, which is a paper-like feature. Moreover, the luminance of the reflective display linearly depends on the ambient illuminance, which is also a paper-like feature, hence the devices with reflective EPs are considered to be suitable particularly for outdoor and/or mobile usage. From the user viewpoint, it is of great interest how the visibility of an EP changes especially under various illuminance conditions. However, the visibility of reflective EPs has not been studied well because an evaluation technique has not yet been established. In this paper, an organoleptic examination method is proposed for evaluating visibility of EPs. One of the key points of the method is that a conventional transmissive LCD is employed as a standard of comparison. The other key point is that the threshold illuminance, above which the visibility of EP was superior to that of LCD, can be extracted by a simple measurement that takes only a few minutes to finish. The first device, EP 1, is an electronic billboard “Albirey” fabricated by Hitachi, equipped with a liquid powder type EP from Bridgestone Corporation. A conventional transmissive LCD, LCD 1, with comparable size was used as the standard device for comparison. The second device, EP 2, is an electronic portable reader “PRS-500” fabricated by Sony Electronics equipped with an electrophoretic type EP from E Ink Corporation. Another electronic portable reader, LCD 2, was “Words Gear” fabricated by Matsushita Electric Industrial employing a transmissive LCD with a comparable size. Major specifications and the photographs of these devices are listed in the table. All the displayed contents were in black-and-white. Specifications of the devices under test. †The viewable area was restricted in the 768x1024 pixel portrait by covering the peripheral areas with black paper as shown in the photographs. ‡Top and bottom areas are used for showing the operation instructions and the page index. The effective pixel area for showing the content is almost comparable to EPD 1. 50
Veritas et Visus Display Standard February 2009 Luminance and Color Measurement for LED Backlights with a Hyperspectral Camera Hsiang-Han Hsu, and Yu-Ping Lan, Industrial Technology Research Institute, Hsinchu, Taiwan Chieh-Hung Lai, ISUZU Optics Corp., Hsinchu, Taiwan A calibrated hyperspectral camera is used for luminance and color measurements for the entire surface of LED backlights. The measurement results are compared and are consistent with the results of point-to-point measurements of the widely-used Topcon spectroradiometer SR-3A. This new hyperspectral camera demonstrates the feasibility and reliability of this application. The results show the maximum differences in luminance and CIE color coordinates measurements are 2.9 % and 0.002, respectively. The schematic image type hyper spectrometer is shown in the figure. It consists of an objective lens, an entrance slit and a prism-grating-prism (PGP) structure. The hyperspectral camera is a line scanning system with high spectral resolutions. The line image of the target is formed by imaging optics and then projected on a CCD imaging sensor. The spectral Light dispersed via PGP structure to CCD image sensor of the hyperspectral CCD camera range of the hyperspectral camera is from 380nm to 1100nm. A 1344x1024 12-bit CCD camera (HAMAMATSU C8484- 05G) was used for the experiment. The entire surface information of the LED backlight is derived by scanning of the target. Digital images of the target are captured by a personal computer via IEEE 1394 interface. Channel-Dependent GOG Model for Colorimetric Characterization of LCDs Chun-Hsien Chou, Ray-Chin Wu, Chih-Cheng Fu, Cheng-Chieh Wu, and Shing-Shi Tseng, Tatung University, Taipei, Taiwan; Chien-Lung Tzou, and Jia-Ming Huang, Chunghwa Picture Tubes, Taipei, Taiwan Accurate colorimetric characterization is an important step in establishing the color management system for LCDs to achieve device-independent color reproduction. The gain-offset-gamma (GOG) model that is accurate enough in describing the tone reproduction curves (TRCs) for CRT displays has been found inadequate for characterizing LCDs due to mainly channel interaction and non-constancy of channel chromaticity. In this paper, a modified GOG model that takes channel interaction and backlight leakage into account is proposed to accurately characterize the TRCs of LCDs. Experimental results indicate that the proposed model outperforms the conventional GOG model in terms of the CIEDE2000 color difference between the XYZ values of the measured color sample and the estimated XYZ values. The effect of channel interaction is considered in the proposed model by measuring the parameters of gain and gamma of the GOG model as functions of input digital counts. Experimental results show that the proposed model outperforms the conventional GOG model and is effective in accurate color reproduction of LCDs. The proposed model is also believed to be helpful in characterizing the color sequential displays that show apparent dependence between color channels. Noise and Resolution in a Dual-Layer LCD Aldo Badano, and Hongye Liang, Center for Devices and Radiological Health, FDA, Silver Spring, Maryland Luigi Albani, FIMI/Philips, Saronno, Italy The noise and resolution characteristics of a dual-layer LCD capable of high luminance range are presented with emphasis on the measurement and analysis methods considering the parallax effect. The results are compared to an identical panel with a single-layer structure. The figure shows a single-pixel line displayed in both front and back layer. As a result of the parallax effect, the lines overlap fairly well at about 15 degrees. The parallax effect is 51
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Display Standard - Veritas et Visus

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