• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.6 s.312
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• pp.33-39
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• 2006

Trichromatic LED backlight renders higher colour gamut and panel transmittance to the LCDs than the phosphor-converted white LED backlight. In realization, however, several technical challenges arise, such as colour shift, due to the ambient temperature change, brightness decrease along with the temperature increase, colour mixing, minimizing the total number of chips and so on. In this paper we designed and tested the low cost temperature compensating circuit, using a thermistor as a temperature compensating element, for stabilizing the brightness and maintaining the colour coordinates of the trichromatic backlight units. By applying the temperature compensating circuit, the decrement rate of the brightness and colour shift rate were achieved by 54% and 51% respectively comparing with uncompensated case.

• The Magazine of the IEIE
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• v.22 no.3
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• pp.92-105
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• 1995

각 분야에서 고화질 고해상도의 Flat Panel Display(FPD)에 대한 요구가 급증하고 있으며, FPD 소자들도 다양하다. FPD를 위한 구동방식은 근본적으로 matrix addroessing 방식을 사용하지만 FPD 소자의 동작 원리, 특성, 구동상의 문제점 등에 따라서 구동방식도 매우 다양하다. 다양한 FPD 소자들이 구동 방식과 구동회로를 다 살펴볼 수 없으므로 본고에서는 FPD소자인 PDP, EL, LED, EC, LCD, DMD, AMA, GLV, FED 등의 동작 원리를 설명하고, 이 소자들 중에서 AMLCD와 dc-PDP 소자의 구동방식과 구동회로에 대하여 논의한다. AMLCD의 구동방식으로는 펄스 구동 방식과 용량 구동 방식을 살펴보고, AMLCD의 문제점들을 극복할 수 있는 방법들을 설명한다. dc-PDP의 구동 방법인 pulse-memory 구동방식과 새로운 pulse-memory 구동 방식을 살펴보았다.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.402-403
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• 2009

A variety of power reduction technologies is introduced and the benefits of the technologies are discussed. PenTile$^{(R)}$ DBLC (Dynamic Brightness LED Control) combined with SABC (Sensor-Based Adaptive Brightness Control) enables to achieve the average LED power consumption to one third. The panel power reduction of 25% can be achieved with low power driving technology, ALS (Active Level Shifter). MIP (Memory In Pixel) is expected to be useful in transflective display because the whole display area can be utilized in reflective mode with power consumption of 1mW.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.121-124
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• 2009

We developed a panel of innovative solution-based approaches for synthesis of multicomponent sulfide phosphor materials. The application of these synthesis strategies allowed for preparation of high-purity and high-brightness $BaAl_2S_4:Eu$ and $Ba_2SiS_4:Eu$ phosphors and led to the discovery of new phosphors suitable for application in the LED-based lighting including $Sr_2ZnS_3:Eu$, $CaBaSiS_4:Eu$ and $(Ba,Sr)_2ZnS_3:Eu$.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.222-224
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• 2008

BLUs(Backlight Units) are major component in LCD(Liquid Crystal Display) industry which occupies 90% or more of worldwide FPD(Flat Panel Display) market. And BLU market is expected to be expanded continuously according to the trend of miniaturization, slimness, low power consumption and low weight. The larger the BLU market scale, the more important standardization of performance evaluation techniques to clearly prescribe the product specification. This document is a generic specification of measurement methods of LED BLU for LCDs. It defines general procedures for quality assessment and gives general rules for measuring methods of LED BLU for LCDs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.294-298
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• 2000

As the LED or LCD technology has been developed, if we use LED or LCD pannel, more wide color range coluld be obtained as CRT monitor. Specially, full color LED display is developed by high brightness blue LED. It can be applicable to display pannel with a long-life, wide visible angle and high brightness. A display pannel shows the images of CRT monitor performed by the main computer. Graphic application in the main computer is therefore more important in the market. Conventional 3D STUDIO, one of graphic softwares, has difficulties in manipulating and understanding the specific terminology so that one may need more time to learn it. We, therefore, developed graphic application which can recycle the conventional 3D images by creating or editing the image easily.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.5
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• pp.382-388
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• 2016

When Flat Panel Display (FPD) is made with backlight module, such as LED TV, it inherently suffers from the non-uniform backlight luminance problem that results in un-even brightness distribution throughout the TV screen. If the luminance of each pixel location of a TV screen as a function of the driving voltage can be measured, it can be used to compensate the non-uniformity of the backlight module. We use a carefully calibrated imaging system to take pictures of a TV screen at different levels of brightness and generate the compensation functions for the driving circuitry to correct the luminance level at each pixel location. Making use of the fact that the luminance of the screen is normally brightest at around the center of the screen and gradually decreases toward the border of the screen, the luminance of the whole TV screen is approximated by a mathematical function of the pixel locations. The parameters of the function are computed in the least square sense by the values of both the pixel luminance sent from the driving circuit and the grayscale value measured from the image taken by the imaging system. To justify the correction system, a simple second order polynomial function is used to approximate the luminance across the screen. When the driving circuit voltage is corrected according to the measured function, the variance of the screen luminance is reduced to one tenth of the one measured from the un-corrected TV screen.

• Proceedings of the Korea Contents Association Conference
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• 2008.05a
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• pp.602-606
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• 2008

LCD is supplied light by BLU(Back Light Unit) and the light represents color by each color filter. Also LCD adjusts the amount of light by controlling liquid crystal between the glass of upper plate and one of lower. However, it is impossible to completely exclude light due to the structural and physical characteristic of liquid crystal. Therefore, on transfering light through optical sheet and liquid crystal, many problems are generated. They are related with energy efficiency and get effective for the contrast of LCD to have lower contrast ratio than other display devices. To solve the problems, many techniques have been studied and developed but don't exist keys to solution for them. Among methods, local dimming is one example to be applied to LCD. In this paper we propose image processing algorithm for local dimming of BLU of LED used as light source. The proposed algorithm extracts maximum luminance signal and lights using each extracted signal on segmented region of BLU. Also the proposed algorithm generates image signal in corresponding to luminance of the segmented region and supplies them with LCD panel to represent image with improving luminance ratio.

• Asian Journal for Public Opinion Research
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• v.9 no.2
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• pp.188-211
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• 2021

Decreasing response rates to traditional survey methods, like face-to-face and telephone interviews, have led survey practitioners around the world to seek new ways of conducting surveys in recent years." The COVID-19 pandemic exacerbated this problem because it made conducting face-to-face interviews even more difficult than before. For example, it made conducting face-to-face surveys infeasible in 2020 in South Korea, and so the Korean Academic Multimode Open Survey (KAMOS) was unable to conduct a planned face-to-face survey to recruit new panel members. The entire 8,514-member panel, established via two-stage probability-based sampling from 2016 to 2019, was invited to take three online/telephone surveys in 2020. Of these panel members, 1,352 responded to at least one survey in 2020. To test to what extent the panel remained representative of the adult South Korean population, we compared the two groups of panel members: those who responded to at least one survey in 2020 and those who did not. After weighting both groups on the basis of age, sex, and geographical area, we analyzed their responses to some of the questions that were asked during multiple rounds of the face-to-face panel-recruiting interviews. Using Cohen's d for survey items that could be analyzed numerically and Cramér's V for categorical items, we were able to conclude that the respondents to the 2020 surveys were equivalent to the non-respondents in terms of both demographics and in the answers they originally gave to substantive questions on a variety of topics related to social science or public opinion research, including questions about quality of life, societal issue, and politics (Cohen's d items <0.2, 95% CI; Cramér's V items <0.1, 95% CI). This analysis may provide a model for others who wish to test the continued representativeness of their panel or who would like to use a different survey mode or change some other aspect of their methodology and test whether it is equivalent to their former methodology. Our success in building a panel that retained its representativeness may be useful to those in other countries where face-to-face surveys had previously been the norm but are becoming increasingly difficult to conduct.

• Transactions on Electrical and Electronic Materials
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• v.17 no.5
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• pp.306-309
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• 2016

The Cs₃Sb photocathode was formed by non-vacuum process technology. An in-situ vacuum device was fabricated successively with flat cesium antimonide photocathode emitters fabricated in a process chamber. The electrical properties of the device were characterized. Electron emission from the devices was induced by photoemitted electrons, which were accelerated by an anode electric field that was shielded from the photoemitter surface. The electrical characteristics of the devices were investigated by measuring the anode current as a function of device operation times with respect to applied anode voltages. Planar blue LED light with a 450 nm wavelength was used as an excitation source. The results showed that the cesium antimonide photocathode emitter has the potential of long lifetime with stable electron emission characteristics in panel devices. These features demonstrate that the cesium antimony photocathodes produced by non-vacuum processing technology is suitable for flat cathodes in panel device applications.