• Journal of Information Display
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• 제11권3호
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• pp.123-127
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• 2010

Fluorescent white organic light-emitting diodes showing high color-rendering indices (CRIs) of up to 81 was demonstrated, with a silicon-cored anthracene derivative (PATSPA) doped with DPAVBi utilized as the deep-blue host and dye materials, and the commercial dyes rubrene and DCM2 utilized as the orange- and red-light-emitting dyes. The devices, consisting of three emissive layers, showed bright-white-light emission, but the ratio of the blue peak to the orange and red peaks changed with the current density and the thickness of the blue emissive layer. A high CRI was achieved with the use of a deep-blue emitter doped in a novel host and by optimizing the blue-layer thickness. The device with a blue-layer thickness of 10 nm showed the Commission Internationale de l'Eclairage (CIE) color coordinate of (0.33, 0.35), a high CRI of 81, and a moderate external quantum efficiency of 2% at a current density of $2.5\;mA/cm^2$.

• 한국태양에너지학회 논문집
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• 제31권2호
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• pp.31-36
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• 2011

LED is expected as an environmentally friendly next generation light source with its good reliability and long lifetime. The light sources for illumination have a variety of applications in the indoor and outdoor, and the variation of optical power and color rendering of the light source limits their applications. Therefore, it is necessary to research the LED lamp and its luminaire to minimize the variation of dynamic characteristics and to improve the color rendering due to that illuminating environment. Daylight is very good light source to human and can be used as primary or a secondary light source with benefits of energy, productivity and health.This paper presents the design method of LED lighting system to improve poor property in terms of CR(color redering) characteristic to use daylight effectively.

• 반도체디스플레이기술학회지
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• 제16권4호
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• pp.11-15
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• 2017

Red phosphors, $Sr_2Si_5N_8:Eu^{2+}$, were synthesized as a single-phase crystal structure by optimizing carbon and $Eu^{2+}$ contents in a carbothermal reduction nitridation method. With increasing $Eu^{2+}$ contents, the photoluminescence spectra were red-shifted from 600 nm peak for 1 mol% for to 700 nm for 7 mol%. It was suggested that this red shift is attributed to the energy transfer from one low-energy sited $Eu^{2+}$ (1) to other high-energy sited $Eu^{2+}$ (2). Finally, the best red sample (620 nm emission peak and 80 nm half width for 3 mole% of $Eu^{2+}$) was packaged on a Blue LED together with two additional green and yellow phosphors, the fabricated White LED showed a high color-rendering index of 90 and white color coordinates of x= 0.321 and y = 0.305.

• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1673-1681
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• 2018

In this paper, the fabrication of a white light-emitting diode (WLED) package capable of producing different color rendering indexes (CRI ($R_a$)) using different types of phosphors (YAG:Ce, Silicate, Nitride, LuAG) for the LEDs is presented. The color quality is evaluated based on the current and temperature variation conditions. The evaluation method for color quality compares the existing CIE 13.3 method and the new IES TM-30-15 method. The CRI ($R_a$) defined in the conventional CIE 13.3 has the disadvantage. This cannot offer any information relevant to the user's preference. However, the newly proposed IES TM-30-15 method suggests the additional measure related to user's preference such as Color Gamut ($R_g$). The present experimental results obtained using the IES TM-30-15 show that the color quality of the WLEDs using green and red phosphors are better than that of the WLEDs using yellow phosphor, but their luminous efficacies are lower. The color quality of WLEDs using green and red phosphors are more stable than that of the WLEDs using yellow phosphor, for current and temperature variations, and it is verified that the phosphor causes this change. The evaluation method for color quality, based on IES TM-30-15, is proved to be capable of overcoming the problems of the existing evaluation methods by this study.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2006년도 추계 종합학술대회 논문집
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• pp.806-810
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• 2006

컴퓨터 그래픽스의 연구는 크게 사실적 렌더링 분야와 비사실적 렌더링 분야로 나눌 수 있다. 사실적 렌더링과 달리 비사실적 렌더링은 만화, 수채화, 해칭과 같은 사람이 손으로 표현한 것 같은 분위기와 특징을 갖는 영상을 표현해 보자는 데 그 목적이 있다고 할 수 있다. 본 연구에서는 비사실적 렌더링 기법의 하나인 실시간 해칭 렌더링기법과 사실적 렌더링기법인 그림자 기법을 통합하여 실시간 해칭 렌더링에서 그림자를 생성하기 위한 방법을 모색하였다. 그림자 기법에는 투영 텍스쳐 그림자 기법을 이용한 그림자 기법을 해칭 렌더링에 적용하여 해칭 렌더링에서 실시간 해칭 그림자를 생성하기 위한 기법을 제시한다.

• 디지털산업정보학회논문지
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• 제8권1호
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• pp.55-64
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• 2012

The advantage of direct volume rendering is to visualize structures of interest in the volumetric data. However it is still difficult to simultaneously show interior and exterior structures. Recently, cone beam computed tomography(CBCT) has been used for dental diagnosis. Despite of its usefulness, there is a limitation in the detection of interior structures such as pulp and inferior alveolar nerve canal. In this paper, we propose an efficient volume rendering model for visualizing important interior as well as exterior structures of dental CBCT. It is based on the concept of illustrative volume rendering and enhances boundary and silhouette of structures. Moreover, we present a new method that assigns a different color to structures in the rear so as to distinguish the front ones from the rear ones. This proposed rendering model has been implemented on graphics hardware, so that we can achieve interactive performance. In addition, we can render teeth, pulp and canal without cumbersome segmentation step.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제4권11호
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• pp.529-536
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• 2015

비사실적 렌더링(NPR; Non-Photorealistic Rendering)은 2차원 영상과 3차원 모델을 대상으로 하는 방법이 다르며 각각의 대상에 NPR을 적용하여 두 콘텐츠를 혼합하면 이질감이 나타나는 문제점이 있다. 본 논문에서는 3차원 객체와 영상에 있어서 각각의 대상에 카툰 및 스케치와 같은 비사실적 효과를 적용하여 조화롭게 혼합하는 기법을 제시한다. 제안 기법은 2차원 영상의 데이터를 분석하여 컬러 분포 특징을 얻고 이를 이용하여 실사 영상이나 3D 객체의 컬러 수를 줄인다. 단순화된 컬러맵과 윤곽선 에지 데이터로부터 비사실적 렌더링을 실시한다. 컬러맵 정보의 추출 및 적용 과정에서 자연스러운 장면 연출을 위해서 영상분할 과정이 필요하다. 그러나 영상분할 기법은 많은 연산을 필요로 한다. 특히 크기가 큰 입력에 대해서는 비사실적 렌더링에 많은 시간이 소요된다. 처리 시간이 많은 영상분할의 고속화를 위하여 GPU(Graphics Processing Unit)를 이용한 병렬 컴퓨팅을 할 수 있는 GPGPU(General-Purpose GPU)를 사용한다. GPGPU의 사용으로 알고리즘의 수행속도를 크게 개선하였다. 또한 영상분할 후 단순화된 컬러를 추출하여 일련의 컬러맵을 생성한 뒤 3D 객체에 NPR을 적용할 때 추출해낸 컬러맵을 적용하여 2차원 영상과 3차원 객채 간의 이질감을 줄이고 조화롭게 하였다.

• ETRI Journal
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• 제35권6호
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• pp.969-979
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• 2013

Various simulation applications for hair, clothing, and makeup of a 3D avatar can provide more useful information to users before they select a hairstyle, clothes, or cosmetics. To enhance their reality, the shapes, textures, and colors of the avatars should be similar to those found in the real world. For a more realistic 3D avatar color reproduction, this paper proposes a spectrum-based color reproduction algorithm and color management process with respect to the implementation of the algorithm. First, a makeup color reproduction model is estimated by analyzing the measured spectral reflectance of the skin samples before and after applying the makeup. To implement the model for a makeup simulation system, the color management process controls all color information of the 3D facial avatar during the 3D scanning, modeling, and rendering stages. During 3D scanning with a multi-camera system, spectrum-based camera calibration and characterization are performed to estimate the spectrum data. During the virtual makeup process, the spectrum data of the 3D facial avatar is modified based on the makeup color reproduction model. Finally, during 3D rendering, the estimated spectrum is converted into RGB data through gamut mapping and display characterization.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 1990년도 추계학술발표회논문집
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• pp.17-22
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• 1990

A computer program to calculate the color temperature (To) and color rendering index (Ra) of the light source was developed. Using this program and a measuring system with a monochromator and a integrating sphere, To and Ra of incandescent lamp and fluorescent lamp was calculated. As a result, it is known that To of the I/L and the F/L with a reactor ballast is changing about 40˚K with varying source voltage of 5 V. Ra variations of these lamps have a trend but can be disregarded.

• 조명전기설비학회논문지
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• 제18권4호
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• pp.15-21
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• 2004

광속구(integrating sphere photometer), 분광기(monochromator)등을 이용하여 노랑색(Y), 녹색(G), 백색(W)의 SMD(surface mounted device)형태의 HB LED(high brightness light emitting diode)에 대한 광속(luminous flux, LF), 상관 색온도(correlated color temperature, CCT), CIE 색도좌표(chromaticity coordinate CC)등 광특성을 실험하여 그 결과치를 비교 분석하였고, 백색 LED에 대해서는 연색지수를 고찰하였다.