대면적 LCD TV용 백라이트 내 반사형 편광판의 광학성능과 백라이트 구조의 상관성에 관한 연구

유진선,고재현,유미연,박승미,김수진 한국물리학회 2010 새물리 Vol.60 No.1

The luminance, the luminance uniformity, the viewing-angle characteristics, and the luminance gain properties of 55-inch LED (light-emitting-diode)-type and CCFL (cold-cathode fluorescent lamp)-type backlights were investigated quantitatively. The luminance gain of the reflective polarizer, one of the most representative brightness enhancement films, was measured for several optical configurations of both backlights. The optical gain for the LED backlight, for which a light guide plate was used, was higher than that for the CCFL backlight, for which a diffuser plate was adopted. This result suggests that the luminance gains achieved by using brightness enhancement films are substantially affected by optical properties such as the reflectance, the absorption, and the polarization-conversion properties of the optical components and light sources in the backlight. This point may be useful in optimizing the optical performances of backlights for LCD applications. 55인치 LCD TV에 적용되는 발광다이오드(Light Emitting Diode, LED)형 백라이트(Backlight)와 냉음극형광램프(Cold Cathode Fluorescent Lamp, CCFL)형 백라이트의 휘도, 시야각 특성, 휘도향상 특성을 정량적으로 평가하여 비교하였다. 특히 대표적인 휘도향상필름인 반사형 편광판에 의한 휘도이득을 다양한 광학필름의 조합 하에 두 백라이트에 대해서 평가하였다. 그 결과 도광판이 적용된 LED 백라이트 내에서의 휘도 이득이 확산판을 사용하는 CCFL 백라이트에 비해 더 높은 것을 확인할 수 있었다. 이러한 결과는 동일한 휘도향상필름을 적용한다고 하더라도 백라이트의 후면 구조가 가지는 반사율과 흡수율, 편광 변환 특성 등에 의해 휘도향상필름의 휘도이득이 달라진다는 것을 의미한다. 이러한 결과는 이후 백라이트의 광학구조 최적화에 있어서 반드시 고려해야 할 광학적 특성의 하나가 될 것이다.

Initial Photometric and Spectroscopic Characteristics of 55-inch CCFL and LED Backlights for LCD-TV Applications

고재현,유진선,유미연,박승미,김수진 한국조명.전기설비학회 2010 조명·전기설비학회논문지 Vol.24 No.3

For better picture quality in LCD TVs, it is important to reach a steady emitting state within as short a time as possible in the initial stage after the TV is turned on. The initial characteristics of LCD TVs are mainly determined by the properties of the backlight. In the present study, the photometric and spectroscopic properties of a 55-inch Cold Cathode Fluorescent Lamp (CCFL) and Light Emitting Diode (LED) backlights were investigated. The measured properties include time dependence of the spectrum, luminance, and color coordinates. The results show that the change in the spectroscopic properties of the LED backlight is smaller than that of the CCFL backlight. This indicates that the initial picture quality of the LCD TV with the LED backlight is superior to that with the CCFL backlight. The origins of this difference were discussed in relation to the inherent characteristics of the two light sources.

Study on the Luminance Properties of Optical Films for Flat-lamp Backlight Applications

Mi-Yeon Yu,Ji-Hee Park,고재현 한국광학회 2008 Current Optics and Photonics Vol.12 No.3

The luminance properties of FFL(Flat Fluorescent Lamp) backlights have been investigated in detail for the first time. The on-axis luminance gain as well as viewing-angle characteristics on various combinations of optical films were obtained from FFL backlight and compared to the results of conventional CCFL(cold-cathode fluorescent lamps) backlights. It was found that the on-axis luminance gains achieved by using optical films in the FFL backlight were lower than those in the CCFL backlight indicating that the recycling processes occurring between optical films and light sources/reflection sheet are not so effective in the FFL backlight due to the much larger area of, and thus higher absorption probability of the FFL. This result suggests that new optical films should be developed for FFL backlight and other flat-lamp backlight technologies.

Initial Photometric and Spectroscopic Characteristics of 55-inch CCFL and LED Backlights for LCD-TV Applications

Jae-Hyeon Ko,Jin-Sun Ryu,Mi-Yeon Yu,Seung-Mi Park,Su-Jin Kim 한국조명·전기설비학회 2010 조명·전기설비학회논문지 Vol.24 No.3

For better picture quality in LCD TVs, it is important to reach a steady emitting state within as short a time as possible in the initial stage after the TV is turned on. The initial characteristics of LCD TVs are mainly determined by the properties of the backlight. In the present study, the photometric and spectroscopic properties of a 55-inch Cold Cathode Fluorescent Lamp (CCFL) and Light Emitting Diode (LED) backlights were investigated. The measured properties include time dependence of the spectrum, luminance, and color coordinates. The results show that the change in the spectroscopic properties of the LED backlight is smaller than that of the CCFL backlight. This indicates that the initial picture quality of the LCD TV with the LED backlight is superior to that with the CCFL backlight. The origins of this difference were discussed in relation to the inherent characteristics of the two light sources.

Initial Photometric and Spectroscopic Characteristics of 55-inch CCFL and LED Backlights for LCD-TV Applications

Ko, Jae-Hyeon,Ryu, Jin-Sun,Yu, Mi-Yeon,Park, Seung-Mi,Kim, Su-Jin The Korean Institute of IIIuminating and Electrica 2010 조명·전기설비학회논문지 Vol.24 No.3

For better picture quality in LCD TVs, it is important to reach a steady emitting state within as short a time as possible in the initial stage after the TV is turned on. The initial characteristics of LCD TVs are mainly determined by the properties of the backlight. In the present study, the photometric and spectroscopic properties of a 55-inch Cold Cathode Fluorescent Lamp (CCFL) and Light Emitting Diode (LED) backlights were investigated. The measured properties include time dependence of the spectrum, luminance, and color coordinates. The results show that the change in the spectroscopic properties of the LED backlight is smaller than that of the CCFL backlight. This indicates that the initial picture quality of the LCD TV with the LED backlight is superior to that with the CCFL backlight. The origins of this difference were discussed in relation to the inherent characteristics of the two light sources.

Optimization of the optical structure of thin direct-lit LED backlights for LCD applications by using micro-LEDs

이정균,고재현 한국정보디스플레이학회 2020 Journal of information display Vol.21 No.1

The optimized optical structure of the micro-LED-based direct-lit backlight was investigated through optical simulation. The backlight consisted of only one diffuser plate and an array of micro-LEDs with a reflection film positioned on the bottom of the backlight. An additional reflector was put on top of each micro-LED to prevent the formation of bright spots. Under several number density conditions of the microbeads in the diffuser plate, stable regions were found on the gap-pitch plot, where a high Mura index of ∼1 was secured. The bead density needed to be small (around 104 mm−3) to maintain above 60% transmittance, because the transmittance of the backlight was significantly reduced at higher bead densities. Under the 104 mm−3 bead density condition, the gap can be reduced to 1.5 mm at a 3 mm pitch. The gap can be further reduced if additional optical films, such as a diffuser sheet, a prism film, and a reflective polarizer, will be adopted in the backlight. This work demonstrated that micro-LEDs are ideal light sources for realizing a thin direct-lit backlight for LCD applications.

LED 백라이트 시스템을 이용한 빛 감지형 액자의 연구

조병권 ( Byung Gwon Cho ) 한국화상학회 2011 한국화상학회지 Vol.17 No.3

A lighted frame using LED backlight system operated by sensing of light was developed including in CDS sensor for sensing brightness. The LED backlight was turned off when the surrounding illumination was bright, and turned on when the surround illumination was dark. A frame was designed that the inside space was sufficient for inserting the LED backlight system and the edge of the frame could hide unnecessary light by a LED backlight. A LED backlight system was designed that a high speed switching transistor operated on and off state by connecting a CDS light sensor to base terminal because a CDS light sensor has a characteristics that a resistance was 0 in the case of bright condition and infinite value in the dark condition. 3 anodes among 9 LEDs with the series and parallel connections was joined to power supply and 3 cathodes was joined to a collector of the transistor. LEDs were light because 3 cathodes were grounded when a transistor turns on and LEDs were dark because 3 cathodes were floating in the off state. It was founded that LED backlight did not operate by the sensor under the bright illumination condition and normally operated when the surrounding illumination was dark.

CIM(Current Injection Method)을 이용한 Charge-Pump 방식의 Plasma Backlight용 고압 Inverter

이준영,장준호,강신호,이경인 전력전자학회 2007 전력전자학회 논문지 Vol.12 No.5

Charge-pump high voltage inverter for Plasma backlight using CIM(Current Injection Method) is proposed in this paper. Adoption of ERC(Energy Recovery Circuit) is a new attempt in high voltage inverter so that it is not only energy recovery but also improvement of discharge stability and system unstability which is interrupted by noise. Using a charge-pump technique enables low voltage switches to be usable, the cost can be reduced. CIM is adopted to achieve high speed energy recovery in proposed circuit. Operations of the proposed circuit are analyzed for each mode. The proposed circuit is verified to be applicable on a 32 inch plasma backlight panel by experimental results. 본 논문에서는 CIM(Current Injection Method)을 이용한 charge-pump방식의 plasma backlight용 고압 inverter회로를 제안한다. 고압 inverter에서 에너지 회수회로의 채용은 새로운 시도로서 에너지회수 이외에도 noise에 의한 시스템의 불안정성과 방전안정화에 기여하고 있다. charge-pump방식으로 스위치류의 내압을 저감하므로 cost면에서 매우 유리한 조건을 확립하였으며 CIM(Current Injection Method)방식의 적용으로 high speed 에너지 회수를 가능하게 하였다. 그리고 제안회로의 동작을 모드별로 해석하였으며, 실제 32" 패널에 적용하여 실험함으로써 제안한 회로의 유용성을 입증하였다.

Simulation study on the optical properties of hybrid films adopted in quantum-dot edge-lit backlights for LCD applications

Lee Jung-Gyun,Lee Gi Jung,고재현 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.6

A new hybrid optical flm integrating several optical functions was adopted in a quantum-dot (QD) backlight for liquid crystal display applications. The hybrid flm included two prism sheets and one refective polarizer between which index-matching layers were inserted. The optical performances of the hybrid QD backlight were comparable to those of a conventional QD backlight where optical flms were separately adopted. The on-axis luminance decreased slightly while the viewing angle became enhanced by adopting the hybrid flm. The color gamut of the present hybrid QD backlight was more than 100% according to the National Television Standards Committee standard. The hybrid flm suggested in this study can be used to reduce the number of optical flms substantially and, thus, the fabrication process of backlights.

새로운 관심영역 추출 방법을 이용한 역광보정

성준모 ( Joon Mo Seong ),이성신 ( Seong Shin Lee ),이성욱 ( Songwook Lee ) 한국정보처리학회 2017 정보처리학회논문지. 소프트웨어 및 데이터 공학 Vol.6 No.6

We have implemented a technique to correct the brightness, saturation, and contrast of an image according to the degree of light, and further compensate the backlight. Backlight compensation can be done automatically or manually. For manual backlight compensation, we have to select the region of interest (ROI). ROI can be selected by connecting the outline of the desired object. We make users select the region delicately with the new magnetic lasso tool. The previous lasso tool has a disadvantage that the start point and the end point must be connected. However, the proposed lasso tool has the advantage of selecting the region of interest without connecting the start point and the end point. We can automatically obtain various results of backlight compensation by adjusting the number of k-means clusters for texture extraction and the threshold value for binarization.