White Point Research Articles

Electrophoretic Deposition of YAG Phosphor on SMD LED

The uniform YAG phosphor layers were deposited onto the ITO glass substrates by electrophoretic deposition (EPD) technique. The more stable deposition condition was found when the electrolytic suspension was stirring. White SMD LEDs were easily achieved by using the directly EPD method, i.e. it is easy to achieve a white light point. For two white EPD LEDs, with and without thin epoxy layer, the chromaticity coordinates were x = 0.311, y = 0.29 and x = 0.311, y = 0.30, respectively. Although there has a uniform light shape for the EPD white LED with a thin epoxy layer, however, the lower luminescence efficiency was found due to the reduction of blue light extraction.

SMPTE Digital Cinema White Gamut Practices Study Group Report

By using the XYZ color space, the SMPTE Standards and Recommended Practices effectively allow for an infinite range of reproducible whites. The numerical color encoding chosen in the standard constrains the available colors at peak luminance (48 cd/m 2 ) to a still-large set. However, SMPTE does not specify which of these encode-able colors are reproducible in exhibition. This means that colors can be mastered (encoded) that may not be seen by audiences in exhibition. Likewise, colors displayed in exhibition may never have been seen in mastering. For example, if your DI mastering suite were set up in RGB for a D55 white point at 48 cd/m 2 , projectors in current digital cinema exhibition practice, using the projector configuration file DCDM_XYZ_239, would not accurately reproduce the encoded master at peak white. Further, there is significant confusion between White Point, the color with maximum possible luminance, and Calibration White, a specific color chosen for calibration or verification purposes. To address these issues a study group was created within the SMPTE 21DC Technology committee. This Study Group was tasked to report on and recommend solutions to these issues noted above. This report will provide definitions of terms that relate to White Gamut, and White Point. It will also report on findings of current practices in both the mastering environment and exhibition community. Finally the report will provide a recommendation for a proposed constrained White Gamut and will seek to point out all relevant SMPTE documents that would need modification to support this proposal. The SMPTE Digital Cinema White Gamut Study Group began its effort in December of 2006. The report was finished in June of 2008 and the Study Group was tasked to provide a demonstration of its findings and consequences to the general Hollywood SMPTE and ASC community. This task was finally completed on March 24, 2009 at the Linwood Dunn Theatre of the Academy of Motion Picture Arts and Sciences during a joint Hollywood Chapter SMPTE and ASC meeting.

The State of the Field: Political Science and Chinese Political Studies

The Journal of Chinese Political Science (JCPS) is publishing a series of special issues, containing retrospective and prospective papers on the state of Chinese political studies, past, present and future. We call upon China scholars worldwide to contribute to these important special issues which will have a significant impact on the intellectual development of the field. Our goal is to disseminate scholarship that can shed light on the ever changing field of Chinese political studies, provide valuable material for scholar teachers and researchers of Chinese politics, and highlight the achievements, problems and issues, and directions of this field. We have witnessed the substantial transformation of China studies, particularly Chinese political studies, in the past 30 years due to changes in China and its rising status in the world as well as changes in our ways of conducting research. As area studies specialists, we are no longer “isolated” from the larger disciplines of Political Science and International Relations (IR) but an integral part of them. A simple survey of the JCPS and other journals reveals that we have applied theories and methods from these larger disciplines to Chinese political studies and that we have sought to meet the standards of scientific research and theoretical relevance in the two disciplines. The scholarship we produce today has advanced far beyond the days of classic Sinology. However, theoretical and methodological approaches in Chinese political studies are very diverse, and substantive issues in various Chinese contexts are being studied from a broader comparative perspective. As Lynn T. White points out in his paper, “Chinese and Asian comparative research can help reverse the methodological narrowness that obscures much actual politics in the world from being studied circumspectly.” Scholars and students in our field still vividly remember texts used in graduate school and innumerable papers published by first rate comparativists such as Sydney Verba, Arendt Lijphart, David Collier, James Mahon, Giovanni Satori, Gary King, David Easton, and many others. All of them have had a great impact on how we J OF CHIN POLIT SCI (2009) 14:225–227 DOI 10.1007/s11366-009-9067-5

A Simulation Study of Improving Viewing Angles Using Composite Uniaxial Compensation Films in Optically Compensated Bend Liquid Crystal Displays

In this study, we use the commercial simulation software, DIMOS2.0, to study improvement of viewing angle performance. Based on concepts of optical phase compensation, optimized conditions of composite uniaxial compensation films are achieved in optically compensated bend (OCB) liquid crystal displays (LCDs). In conditions of D65 illumination for compensated cells, it shows that viewing angles with contrast ratio over 10 are in the ranges of horizontal 100° and perpendicular 130°. No gray scale inversion occurs within polar angle of 70° at horizontal direction. According to definition of CIE 1931, color coordinate of white point in non-compensated and compensated simulated cells are (0.29634, 0.32592) and (0.27143, 0.29306) at on-axis viewing direction, respectively. Contrast ratio is over 3000 at on-axis viewing direction.

“MAKING THE GHOST WALK ABOUT AGAIN AND AGAIN”: History as Séance in the Work of Susan Howe

“MAKING THE GHOST WALK ABOUT AGAIN AND AGAIN”: History as Séance in the Work of Susan Howe

High fidelity color reproduction of plasma displays under ambient lighting

This paper proposes a method of color reproduction that considers the observer's viewing conditions and characteristics of a PDP display. In general, ambient lighting requires compensation to provide the same visual perception when the temporal and spatial conditions change. In a conventional method, the image contrast and saturation are enhanced by controlling the voltage gain in each channel to consider the phenomenon of human adaptation. Yet, this method encounters difficulties in reproducing the perceived stimulus under a variety of viewing conditions. Accordingly, this study characterizes a PDP display based on the white point when considering the average picture level of the PDP display as the maximum luminance value of a PDP display varies according to the average picture level. Next, to consider the viewing conditions, information on the ambient lighting is obtained using a sensor. The flare, the reflected ambient lighting, is also eliminated on the surface of the PDP display. Finally, the color values are calculated using a modified chromatic adaptation model. In experiments, images reproduced using the proposed method were visually superior to those reproduced using a conventional method.

Monochromatic geometric k-factors in red-blue sets with white and Steiner points

We study the existence of monochromatic planar geometric k-factors on sets of red and blue points. When it is not possible to find a k-factor we make use of auxiliary points: white points, whose position is given as a datum and which color is free; and Steiner points whose position and color is free. We present bounds on the number of white and/or Steiner points necessary and/or sufficient to draw a monochromatic planar geometric k-factor.

From white points to yellow plaques: magnifying endoscopic features of duodenal lymphangiectasia

From white points to yellow plaques: magnifying endoscopic features of duodenal lymphangiectasia

Acknowledgments

The editors would simply like to conclude our second issue, Archaeology and Ethnography of Cultural Heritage Management, by thanking the people who were instrumental in putting this issue together. Special thanks go to Paul Shackel and David Gadsby of the University of Maryland for recruiting experts in cultural heritage research and practice among their colleagues, and for prodding them along as needed. We also offer sincere thanks to Antoinette Jackson of the University of South Florida for providing the same kind of assistance with her students. This was truly a cooperative venture between two universities that are dedicated to promoting cooperation between archaeologists and cultural anthropologists in the protection and management of cultural resources and, as Cheryl White points out in her article, ultimately protecting people whose cultural integrity and lives are threatened. At a time when anthropology is increasingly threatened by division and fragmentation, it is nice to be reminded that ethnographers and archaeologists can come together to work on both scholarly, humanitarian and practical issues of great importance. Thirdly, we offer special thanks to Erve Chambers for providing an excellent overview of cultural heritage studies in his introduction to this issue. As always, thanks to Neil Hann for keeping us on track, dealing with last minute substitutions and getting everything to fit together.

Quantitative PCR Method To Measure the Fungal Endophyte in Locoweeds

A fungal endophyte ( Undifilum oxytropis ) has been implicated in the synthesis of swainsonine in Oxytropis and Astragalus species, commonly known as locoweeds. A quantitative PCR method has been developed to measure the amount of endophyte in Oxytropis and Astragalus species. The limit of quantitation was estimated to be 0.2 pg of endophyte/ng of total DNA. This method of analysis was used to quantify the amount of endophyte in 10 plants each of Oxytropis sericea (white point locoweed), Astragalus mollissimus (wooly locoweed), and Astragalus lentiginosus (spotted locoweed). A significant amount of individual plant variability was observed in endophyte content among individuals in all three species. In one O. sericea and one A. lentiginosus plant swainsonine concentrations were near or below the limit of detection. These plants also had the lowest amounts of endophyte when compared to the other specimens. This method will be a useful tool in further investigating the role the endophyte plays in swainsonine production in various locoweed species.

14.3: Distinguished Paper: White Point Calibration of Color Sequential Mobile Projector

AbstractColor sequential RGB LED driving architecture becomes popular for mobile projectors of which the output are under 10 lumens. One of the difficulties of color sequential projector lies in how to make white balance by mixing RGB color. LED bins and coupling tolerance are diverse so that they have sensitive effects on color temperature distribution. In this paper, the analyses of color temperature distribution and a practical calibration method will be presented.

New Dermoscopic Pattern in Actinic Keratosis and Related Conditions

T HE LESIONS SHOWN IN THIS ARTICLE ARE from the upper lip of an 85-year-old woman (Figure 1, inset), the malar of a 67-year-old man (Figure 2, inset), and the forehead of a 56-year-old man (Figure 3, inset). They correspond to actinic keratosis (AK) (case 1), lichenoid AK (case 2), and squamous cell carcinoma that developed on an AK (case 3). Polarized contact dermoscopy of all 3 lesions revealed a pattern called a rosette sign (Figures 1-3, arrows), a term coined by Lester Cowell, MD, and is characterized by 4 white points arranged as a 4-leaf clover (Figure 4) mainly localized inside the follicular openings. Histologically, the rosette sign may correspond to changes of orthokeratosis and parakeratosis (flag sign) (Figure 5 [case shown in Figure 3]). It is occasionally seen in AK and related conditions and could help in their diagnosis. It does not appear in nonpolarized contact dermoscopic images and may therefore represent a tissue and polarized light phenomenon.

The Relationship between Saccadic Suppression and Perceptual Stability

Introspection makes it clear that we do not see the visual motion generated by our saccadic eye movements. We refer to the lack of awareness of the motion across the retina that is generated by a saccade as saccadic omission [1]: the visual stimulus generated by the saccade is omitted from our subjective awareness. In the laboratory, saccadic omission is often studied by investigating saccadic suppression, the reduction in visual sensitivity before and during a saccade (see Ross et al. [2] and Wurtz [3] for reviews). We investigated whether perceptual stability requires that a mechanism like saccadic suppression removes perisaccadic stimuli from visual processing to prevent their presumed harmful effect on perceptual stability [4, 5]. Our results show that a stimulus that undergoes saccadic omission can nevertheless generate a shape contrast illusion. This illusion can be generated when the inducer and test stimulus are separated in space and is therefore thought to be generated at a later stage of visual processing [6]. This shows that perceptual stability is attained without removing stimuli from processing and suggests a conceptually new view of perceptual stability in which perisaccadic stimuli are processed by the early visual system, but these signals are prevented from reaching awareness at a later stage of processing.

Vertically‐stacked color‐tunable LEDs

AbstractLight‐emitting diodes with vertical stacking geometry were fabricated and characterized. Color‐tunable emission and white‐light emission has been demonstrated in Stacked‐LED (SLED). Emissions of different colors, ranging from green‐blue, to pink‐purple, to yellow‐orange and white light emission have be achieved by adjusting the relative intensity of two or three individual emission bands, which in turn are controlled by adjusting voltage supply. Compared to conventional lateral side‐by‐side geometry, the shift of white color chromaticity with respect to viewing angles is less in the case of SLED device. The farthest shift of white CIE coordinate point away from the pure white CIE coordinate is (0.29, 0.29) in SLED compared to (0.37, 0.35) in the commerical available lateral packaged structure. This vertically‐stacked LED is poised to open new frontiers in high performance color‐tunable LEDs. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Performance analysis of PLED based flat panel display with RGBW sub-pixel layout

PLED based flat panel displays with RGBW sub-pixel format utilizing a white emitter as the fourth primary, was analyzed theoretically and experimentally. Instead of the traditional white point characterization method, uniform luminance color space was introduced to characterize the display performance in a more realistic way. In the uniform luminance color space, after the power efficiency of the white emitter exceeds a threshold determined by the green emitter’s efficiency, the RGBW display becomes more energy efficient than the RGB display. To simulate the display performance in different applications, such as computer desktop visualization, or video application, the color usage frequency with Gaussian distribution was adopted. As the color usage frequency distribution gets closer to that in the real images, the full color pixel’s power efficiency of the RGBW display is more and more dependent on the EL performance of the white emitter. With a highly efficient white emitter as W sub-pixel, the RGBW display will be the preferable choice for displaying video information.

Balanced Full-Color White Organic Light-Emitting Devices with Simple Double-Emissive-Layer Structure

White organic light-emitting devices (WOLEDs) were realized using a simple four-layer structure to obtain red, green and blue emissions for color mixing. A fluorescent dye of 3-(dicyanomethylene)-5,5-dimethyl-1-(4-dimethylamino-styryl) cyclohexene doped in tris(8-quinolinolato) aluminum matrix and a thin N,N'-bis(1-naphthyl)-N,N'-biphenyl-1,1'-biphenyl-4,4'-diamine layer were constructed to act as the dual emitting layer. The device showed a current efficiency of 5.0 cd/A with a luminance of 2020 cd/m2 and Commission Internationale De L'Eclairage (CIE) coordinates of (0.32, 0.32) at 11.6 V, and a maximum luminance of 12580 cd/m2 at 330 mA/cm2 (17 V). A good color rendering index of 85 was obtained. Three main emission peaks at 440, 530, and 630 nm were steadily balanced with the CIE coordinates near the optimum white point of (0.33, 0.33) over 9 V. This was attributed to the modification of appropriate energy transfer in the doping system and the confinement of the recombination zone within two emitting layers.

Color measurement for RGB white LEDs in solid-state lighting using a BDJ photodetector

Color measurement and white balancing for RGB white LEDs was demonstrated by a blue-violet enhanced BDJ photodetector, which can simultaneously determine the centroid wavelength and the radiant power of LEDs from 380 nm to 780 nm. This BDJ photodetector directly gave the chromatic coordinates of a LED that was approximated as a monochromatic stimulus due to its narrow spectrum compared with the CIE color-matching functions. Maximal simulated and experimental errors Δ u′ v′ to the target white point of the white balanced RGB LEDs was 0.0154 and 0.0214. The BDJ photodetector also performed to be sensitive to the spectrum variation characterized by CCT, and was preferable as a sensor for monitoring the white point.

Colour representation methods for segmentation of vegetation in photographs

Papers dealing with vegetation segmentation from RGB images confound the effect of colour representation with a clustering algorithm. In this paper, various colour representations of RGB images are compared. On a set of images, vegetation and soil pixels were manually isolated to form two known populations for each image. For each pixel in the populations, a quadratic discriminant analysis was applied. The comparison between colour representation methods was based on classification errors. Two image sets were used. One was under controlled flash illumination and the other one was under uncontrolled outdoor lighting. Images acquired under controlled illumination were transformed to simulate illuminants corresponding to other correlated colour temperatures (CCT) covering most situations that can be encountered under natural lighting in the field. Under controlled illumination, the error rates for both vegetation and soil pixels were more influenced by the site, crop or CCT than by the projection method. Based on robustness with respect to the white point definition coupled to good balance between classification errors for soil and vegetation pixels, it is concluded that the L∗a∗b∗ projection is the best projection for segmenting green vegetation against a soil background using consumer-grade charge-coupled device (CCD) cameras.

Investigation of Pr-doped fluoride crystals as possible white-light emitters

White-light emission from BaY 2F 8, KYF 4, KY 3F 10 and LiLuF 4 samples with different Pr 3+ doping levels from 0.3% to 3% is described. We report here their CIE chromatic coordinates and the intrinsic emission efficiency as the ratio of the absorbed and the emitted signal. Optical absorption spectra and luminescence spectra were acquired at room temperature after visible pumping. The calculation of Commission Internationale de l’Eclairage (CIE) coordinates shows that white emission is obtained from all the samples independent of both the doping level and incident power. The CIE coordinates closest to the white point are (0.35, 0.32) from the 0.3% Pr 3+:BaY 2F 8 sample. We also measured the intrinsic emission efficiency of all the crystals. The best obtained is 60%.

Preparation and optical properties of transparent Ce:YAG ceramics for high power white LED

Transparent Ce:YAG ceramics were synthesized from the Ce:YAG powder which was produced by co-preparation method of the hydroxides. The Ce:YAG ceramics exhibit a broad emission band peaked at 530 nm due to the 5d→4f transition of Ce3+. The transmittances of the samples obtained were 70 ∼ 87 % at 800 nm. The absorption coefficient and emission intensity of Ce3+ were increased with the increase of the thickness. With increasing thickness of the sample, the color coordinates of the Ce:YAG ceramics under 465 nm LED excitation shifted from the blue region to the yellow region with passing nearby the theoretical white point. The highest value of luminous efficacy of the white LED was 73.5 lm/W.