• Current Optics and Photonics
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• v.3 no.6
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• pp.590-596
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• 2019

To improve the color gamut of a liquid-crystal display (LCD), we propose a bandpass filter that is added to the backlight unit to optimize the backlight spectrum. The bandpass filter can only transmit red, green and blue light in the visible range, while reflecting the unwanted light. We study the optical properties of the bandpass filter using the transfer-matrix method, and the effect of the bandpass filter on the color gamuts of LCDs is also investigated. When a bandpass filter based on a 5-layer configuration comprising low and high refractive indices ((HL)²H) is used in phosphor-converted white-light-emitting diode (pc-WLED), K₂SiF₆:Mn⁴⁺ (KSF-LED), and quantum-dot (QD) backlights, the color gamuts of the LCDs improve from 72% to 95.3% of NTSC, from 92% to 106.7% of NTSC, and from 104.3% to 112.2% of NTSC respectively. When the incident angle of light increases to 30°, the color gamuts of LCDs with pc-WLED and KSF-LED backlights decrease by 2.9% and 1% respectively. For the QD backlight, the color gamut almost does not change. When the (HL)²H structure is coated on the diffusion film, the color gamut can be improved to 92.6% of NTSC (pc-WLED), 105.6% of NTSC (KSF-LED), and 111.9% of NTSC (QD). The diffusion film has no obvious effect on the color gamut. The results have an important potential application in wide-color-gamut LCDs.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.7-9
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• 2011

본 논문은 LED 백라이트 구동을 위한 전력변환 제어기 설계 및 동특성에 대해 설명한다. 또한 근래 산업계에서 널리 사용하는 operational transconductance amplifier(OTA)와 operational amplifier(op-amp)의 상관관계를 분석하여 각각의 소자를 이용한 최적 제어기를 설계하였다. 설계와 해석을 위해 PSIM 시뮬레이션을 사용하였으며 구현한 PSIM 모델은 실험을 통하여 타당성을 증명하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04a
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• pp.70-71
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• 2009

Photoelectric characteristics of a hydrogenated amorphous silicon thin film transistor(a-Si:H TFT) were obtained for the illumination from various backlight sources and the results were compared and analyzed in terms of the photon energy spectral characteristics of the backlights obtained from the integration of the multiplication of the photon energy and the spectral intensity at etch wavelength. It was possible to conclude that the absorption of illuminated backlight to a-Si:H layer and the generation of electrons and holes are mainly carried out at the wavelength less than 500nm.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1327-1330
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• 2008

A novel fiber optic solution is provided to efficiently mix visible colors. Full color synthesis was achieved utilizing a novel $3{\times}1$ hard polymer clad fiber (HPCF) coupler along with red, green and blue (RGB) light emitting diode (LED) primaries. Varying the intensities of RGB LEDs that are coupled to three input ports, the device rendered a full color with an ultra wide CIE color gamut. Potential applications in pica-projection displays and LED backlights will be discussed.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1606-1609
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• 2008

In this paper, we present a novel process for the realization of large area, low cost field emission cathodes. The process makes use of alumina substrates, which are anodically oxidized in order to yield porous structures capable of hosting metal catalyst nanoparticles. By carefully controlling the final stage of the anodisation as well as the electrodeposition conditions, it is possible to fine tune the density of such catalysts in the range of $10^8-10^9/cm^2$. The catalytic growth of CNTs is subsequently performed at low temperature (${\sim}\;600^{\circ}C$ or below, thanks to the use of $H_2O$), using plasma enhanced chemical vapour deposition. There is no lithography need to make the cathode and current densities of ${\sim}\;1mA/cm^2$ are easily obtained.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1157-1160
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• 2005

In order to improve the image quality of a large size LCD-TV, the Area-Focused Luminance Control (AFLC) technology with data processing algorithm has been developed. The AFLC backlight consists of 16 U-shaped lamps, and controllable areas are divided into 8 blocks. Based on the AFLC technology, the backlight luminance of each block is automatically and separately controllable. Consequently, the contrast ratio is greatly enhanced whereas the corresponding power consumption is decreased as compared with those of conventional backlights.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05a
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• pp.123-127
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• 2004

Cold cathode fluorescent lamp (CCFL) has been used as a light source for direct type backlights for LCD monitors or TV. One inverter for one CCFL was necessary for maintaining the lamp current so that many inverters were used to drive as many CCFLs of direct type backlight for LCD TV. An inverter for driving 16 CCFLs was developed to reduce the backlight cost. The length and diameter of CCFL were 450mm and 4mm, respectively. Backlight including 16 CCFLs for 26" LCD TV was assembled by using one inverter. The uniformities of the assembled backlight operated by the conventional inverter and the newly developed inverter were 75% and 88%, respectively.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06d
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• pp.428-431
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• 2010

LED 백라이트는 그 효율, 활용도 및 환경친화성으로 인해CCFL 백라이트를 대처 할 수 있는 좋은 대안이다. 현재 다양한 LED 백라이트 구성방식이 사용되고 있으며, 전력 절감과 명암대비 향상을 위한 다분할 제어방법(local-dimming)도 다양하게 제안되고 있다. 하지만 다분할 된 LED 백라이트의 제어 해상력은 LCD 패널의 해상력에 비해 상대적으로 매우 낮다. 이런 차이는 백라이트 제어 시 사람에게 인지되는 심각한 왜곡을 발생 시키며, 왜곡을 보상하여 극복하기 위해서는 많은 고려사항들을 파악해야 한다. 본 연구는 백라이트의 정확한 제어를 위해 주변 밝기를 고려하는 Cooperative Dimming방법을 제안하고 있으며, 본 제안 기술을 이용하여 요구 밝기를 최대한 만족하는 정확한 제어를 하며, 동시에 전력 소비를 최소화 하는 제어방법을 제안한다.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.693-696
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• 2009

The ray-tracing technique was used to optimize the light guide plate for the purpose of improving the on-axis luminance on the edge-lit backlights. One-dimensional prisms and engraved V-shaped patterns were applied to the upper and the lower surfaces of the light guide plate, respectively. By optimizing the apex angles of these micro-structures, as well as the shape of the reverseprism film put over the light guide plate, highly-collimated light-output distribution could be obtained on the backlight, which may contribute to the development of mobile LCD's with low power consumption.

• Journal of the Optical Society of Korea
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• v.17 no.6
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• pp.506-512
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• 2013

Recently, the color separation issue of wide-spreading white LEDs has attracted attention due to their wide applicability as light sources in direct-lit LCD backlights. These wide-spreading LED packages usually consist of LED chips, a color-conversion phosphor layer, and a light-shaping lens. The technical aspect of this color issue was related to a method for balancing the yellow spectral component emitting from phosphors with respect to the blue one from the LED chip as a function of viewing angle. In this study, we suggested an approach for carrying out quantitative analysis for the color separation problem occurring in wide-spreading LED packages by optical simulation. In addition, the effect of an internal scattering layer on the color uniformity was investigated, which may be considered as a potential solution for this problem.