• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 및 기술 세미나 논문집 디스플레이 광소자
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• pp.27-28
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• 2008

We have studied an organic layer-thickness dependent electrical and optical properties of organic light-emitting diodes in a device structure of ITO/TPD/$Alq_3$/LiF/Al. While a hole-transport layer thickness of TPD was varied from 35 to 65nm, an emissive layer thickness of $Alq_3$ was varied from 50 to 100nm. A ratio of those two layers was kept to about 2:3. Variation of the layer thickness changes a traverse time of injected carriers across the organic layer, so that it may affect on the chance of probability of exciton formation. Current-voltage-luminance characteristics of the devices show that there are typical rectifying behaviors, and the luminance reaches about $30,000cd/m^2$. Thickness-dependent current efficiency shows that there is a gradual increase of the efficiency as the total layer thickness increases. The efficiency becomes saturated to be about 10cd/A when the total thickness is above 140nm. They show that emission was from the $Alq_3$ layer, because the peak wavelength is about 525nm. View angle-dependent emission spectra show that the emission intensity decreases as the angle increases.

• 대한전자공학회논문지SP
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• 제38권5호
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• pp.529-537
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• 2001

대형 디스플레이 화면에 대한 소비자의 선호도가 증가함에 따라 3관식 프로젝션 (projection) 텔레비전의 수요가 늘고 있다. 그러나 3관식 HD (high definition) 프로젝션 TV에서는 직시형 CRT (Cathode Ray Tube)를 사용하는 TV보다는 단위 면적당 절대 밝기가 어둡다. 또한 프로젝션 TV에 사용되는 인광체의 색재현 영역 (gamut)이 기존의 NTSC (National Television System Committee) 표준과 다른 것을 사용하고 있다. 본 논문에서는 3관식 프로젝션 HDTV의 RGB 인광체 좌표와 RGB 빔 전류비의 관계를 색온도 변화에 대하여 해석하고, 전류비에 따른 빔 프로파일의 변화에 의한 영상의 열화와 시각 특성인 Helmholtz-Kohlrausch 효과를 고려하여 시청자가 느끼는 밝기를 최대화하기 위한 기준 백색 (reference white)의 범위를 제안하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1221-1224
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• 2005

The improvement of luminance and luminous efficiency is the one of the most important parts in AC-PDPs. To achieve high luminance and luminous efficiency, high VUV emission efficiency is needed. We measured the emission spectra of the vacuum ultraviolet(VUV) rays in surface discharge AC-PDP with ternary gas mixture of He-Ne-Xe. The influence of He-Ne-Xe gas-mixture ratio on excited $Xe^{\ast}$ resonant atoms and $Xe_2\;^{\ast}$ dimers has been investigated. It is found that luminous efficiency of ternary gas mixture, He-Ne-Xe, is shown to be much higher than that of binary gas mixture of Ne-Xe. For improving discharge luminous efficiency, we have studied VUV emission characteristics of ternary gas mixture, He(50%)-Ne-Xe and He(70%)-Ne-Xe with Xe concentration and filling gas pressure.

• Journal of Information Display
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• 제4권2호
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• pp.19-24
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• 2003

In order to improve the device performances of organic electroluminescent devices (OELDs), the efficiency of carrier injections into the organic layers from electrodes and the balance of injected carrier densities in the emission region are critical factors. Especially, energy barriers, which exist at the interfaces between electrodes and organic layers, interrupt carrier injections, which lead to unbalanced carrier densities. In this study, ${\alpha}-septithiophene$ (${\alpha}$-7T), as a buffer layer, and composite cathode composed of Al and CsF were formed to improve hole and electron injections, respectively. The orientations of ${\alpha}$-7T molecules were adjusted using the simple rubbing method and the mass ratio of CsF was varied from 1 to 10 wt%. Upon investigation of we believe that the 3 wt% mass ratio of CsF and the horizontal orientation of ${\alpha}$-7T molecules are the optimized conditions for achieving better the performance of OELDs. Device with the horizontally oriented 20 nm thick ${\alpha}$-7T layer and composite cathode shows a turn-on voltage of 7V and luminance of 172 cd/$m^2$ at 4 mA/$cm^2$.

• 한국전기전자재료학회논문지
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• 제24권8호
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• pp.664-668
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• 2011

In this study, we have fabricated the red OLED (organic light emitting diode). The basic device structure is ITO/hole transporting layer, TPD(500 $\AA$)/red emitting layer, Alq3 doped with DCM2:rubrene(20 $\AA$)/electron transporting layer, Alq3(M) (500 $\AA$-M $\AA$)/LiF(15 $\AA$)/Al(1,000 $\AA$). The thickness of electron transporting layer(500 $\AA$-M $\AA$) changed 0, 20, 40, 60 $\AA$. Turn on voltage of the red OLED was 5 V, 6 V, 6.5 V and 7.5 V, respectively with electron transfer layer changed ratio. Luminance of red OLED was 4,504, 1,840, 1,490 and 1,130 cd/$m^2$, respectively. Optimized electron transfer layer position changed ratio of the red OLED was 0 $\AA$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.438-440
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• 2005

At present, characteristic of high color reproduction for LCD TV is needed in Display market according to start mass production of LCD TV. Therefore development target for LCD is focused on improvement of color reproduction. The improving methods of high color reproduction are alteration of color Filter or Red, Green, Blue phosphor alteration of CCFL. But decrease of luminance and panel transmittance is caused by alteration of Color Filter. Accordingly, we completed LCD with high color reproduction by the most suitable emission spectrum of CCFL phosphor at panel with conventional color filter. In this experiment, we knew that LCD applied to CCFL with high color rendering characteristic had color reproduction range of 81% compared with NTSC in CIE color coordinate. According to increase of intensity peak and alteration of Red, Green, Blue phosphor spectrum, we made LCD with high color reproduction characteristic. In conclusion we achieved improvement of color reproduction ratio by alteration of CCFL phosphor without changing color filter.

• 대한의용생체공학회:의공학회지
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• 제44권4호
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• pp.242-254
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• 2023

Although upper respiratory tract infections (URTIs) are common diseases, there have been no studies of their relationship with the indices obtained from tongue image analyses. The purpose of this study was to identify a tongue index through an analysis of tongue images (TIs) showing significant changes before and after treatment in patients with URTIs. A computerized tongue image acquisition system was developed to acquire TIs from subjects in the same environment. An image was taken from each of 39 URTI patients and 39 healthy controls. For the patients, images were acquired before and after treatment to identify changes. The tongue area was classified into a tongue body and a tongue coating, and the coating ratio between the two areas, the average value of the colour of each area, and teeth marks were calculated. No significant difference was observed in age or sex between the URTI patients and control participants. Heart rates were slightly different. The analysis of TIs showed that the luminance of the tongue coating and the coating area ratio were decreased, while the reddish value of the tongue body at the centre area increased as the treatment progressed. Tongue coating and body in URTIs had different colour and shape from those in the normal. It is expected that this result will contribute not only to the objectification of traditional Chinese medicine but also to diagnostic methods that do not involve face-to-face physician visit during the pandemic.

• 대한전자공학회논문지SP
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• 제44권2호
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• pp.63-73
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• 2007

본 논문에서는 실외 환경에서 모바일 디스플레이에 발생하는 명순응 현상과 섬광(flare)을 고려하여 주변광원에 적응적인 모바일 디스플레이에서의 색 재현을 제안하였다. 실외 환경에서 디스플레이된 영상은 인간 시각의 명순응 현상에 의해서 어둡게 인지되고 섬광으로 인하여 장치의 밝기는 다소 높아지지만 채도가 감소하는 현상이 발생한다 이러한 현상을 해결하기 위하여 입력 영상의 밝기를 향상하고 채도를 보상하여 실외에서 영상을 보더라도 실내에서와 유사한 영상으로 인지되도록 하였다. 첫째, 주변광원의 밝기는 조도센서를 사용하여 측정하고, 디스플레이의 반사율을 측정하여 해당 조도 하에서의 섬광을 계산하게 된다. 영상의 밝기는 주변광원의 밝기에 따라 변화하는 추상체(cone) 응답이 선형적으로 되도록 역변환 하여 향상하였다. 다음은 섬광으로 인하여 발생하는 물리적인 채도 저하 현상은 이것이 발생하기 전과 후의 차를 이용하여 그 크기만큼을 보상해 주었다. 결과적으로 제안한 방법을 적용한 영상을 실외 환경에서 보았을 때 기존의 어둡게 보이고 채도가 낮아지던 현상이 향상됨을 실험을 통하여 알 수 있었다.

• 한국광학회지
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• 제21권6호
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• pp.247-253
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• 2010

본 논문에서는 에지 방식의 BLU(Backlight unit)에 사용되는 도광판의 구조를 최적화하여 광학시트를 줄이면서 휘도와 균일도 및 시야각을 유지하기 위한 이중구조의 도광판을 설계하고 시뮬레이션을 통해 휘도와 균일도를 알아보았다. 여기에 사용된 복합 도광판은 이중구조의 도광판으로 상부에는 곡률 R을 갖는 프리즘패턴을 형성하고 곡률 R에 따른 휘도와 균일도를 시뮬레이션하였다. 하부에는 V groove 패턴을 회전시켜 상부패턴과 $90^{\circ}$를 이루게 하여 균일도를 확보하였다. 특히, 하부 패턴에서는 외곽의 피치 간격과 중심의 피치간격의 비(최대:최소), 패턴의 개수와 패턴의 분산을 정의할 수 있는 프로그램을 설계하여 V groove 사이의 간격을 결정하였다. 복합 도광판(dual-layer light guide plate, DLGP)의 최적화를 위해 다시 하부 패턴의 개수를 변화시켜 균일도를 알아보았다. 시뮬레이션 결과 복합 도광판을 이용한 BLU는 균일도 90.6%, 시야각 $145^{\circ}$인 특성을 갖는 것을 확인하였다.

• 센서학회지
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• 제29권2호
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• pp.133-140
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• 2020

This study proposes a method of blending visible and near infrared images to enhance edge details and local contrast. The proposed method consists of radiance map generation and color compensation. The radiance map is produced by a Laplacian pyramid and a soft mixing method based on principal component analysis. The color compensation method uses the ratio between the composed radiance map and the luminance channel of a visible image to preserve the visible image chrominance. The proposed method has better edge details compared to a conventional visible and NIR image blending method.