LED Backlight Unit Research Articles

P‐11.8: DCI‐P3 Representation by Using Nano‐IPS Technology

DCI‐P3 color space for digital movie projection is replacing Adobe RGB color space in Wide Color Gamut (WCG) monitor market. Nano‐IPS technology can achieve DCI‐P3 color space by using new advanced phosphors which can enlarge red and green color coordinates in LED backlight unit. This technology does not need to use WCG color filter panel, but need to use general high transmittance color filter panel.

Thermal deformation of microstructure diffuser plate in LED backlight unit

Thermal deformation of microstructure diffuser plate in LED backlight unit

전력 최적제어 기능을 가진 LED 드라이버 설계

LEDs have small size, long lifespan, high reliability, low power consumption and high color efficiency. Using such a characteristics, LED Back Light Unit has been studying actively. This paper proposes LED driver to minimize power consumption due to LED forward voltage(V<SUB>F<SUB>) difference and temperature rising. Compared to conventional LED driver, the proposed driver have excellent stability, brief structure and linear output voltage of DC-DC boost converter. Proposed LED Driver circuit was designed using 0.35um CMOS technology. And its operation was verified through simulation.

6.4: Multi‐mode LCD with Wide View Angle and High Reflectance for Sunlight Readability

AbstractA multi‐mode liquid crystal display LCD is proposed which typically shows color images in the transmissive mode and the transflective mode, and black and white images in the reflective mode. The multi‐mode LCD has the advantages of wide view angle and high reflectance for sunlight readability with low power consumption. A 10.1″ multi‐mode 3Qi LCD with LED backlight unit is demonstrated with wide view angle and 27% reflectance ideal for both notebook and electric reader applications.

P‐201L: Late‐News Poster: A Large‐Sized Directional LED Backlight Unit with Hollow Cavity Light Guide

AbstractAn innovative large‐sized directional LED backlight unit with hollow cavity light guide is devised for autostereoscopic 3D displays by implementing bilateral symmetry bumpy structures in bottom reflector. Simulation results demonstrate a good 3D BLU performance by accommodating only a 3D film as the top emission surface.

大尺寸LED背光源网点的设计及优化

Adopting LED as the light source, LCD TV has significant advantages over adopting Cold Cathode Fluorescent Lamp (CCFL). Light guide plate (LGP) with a two-dimensional array of dots scheme is the key to the design of the LED backlight unit (BLU). A LED BLU with 1.066 8 m in diagonal and 4 mm in thickness, using incidence structure with four-side light sources is proposed in this paper. Considering the complexity and time-consuming process of the large scale LGP dot-pattern design, the method of simplified model is introduced which is the simplification of the LGP and the LEDs. The optimization result between the simplified model and the actual model can be ignored. The LGP luminance uniformity reaches up to 90% and the extraction efficiency is around 50%. Adopting the same method to a BLU with 1.422 4 m in diagonal and the thickness of 3 mm, it also achieved a good result. The luminance uniformity reaches 85% and the extraction efficiency is around 50%.

Local dimming algorithm and color gamut calibration for RGB LED backlight LCD display

A 32 in RGB LED backlight unit is developed. A local dimming algorithm is designed for the backlight, and grid-noise artifacts in the LC driving signal are successfully removed with consideration of the backlight distribution to provide identical intensity from each LED block. The 32 in RGB LED backlight LCD display has achieved a static display contrast of over 20000:1 and an average power reduction of 30%. We have also obtained the color gamut transformation matrix for transferring a cold cathode fluorescent lamp BLU LCD display gamut system to our RGB LED BLU LCD display gamut system, and extended the color saturation by suppositional color expansion method. As a result, the color has been accurately reproduced in RGB LED BLU LCD display with more richness and more saturation.

51.2: New 240Hz Driving Method for Full HD &amp; High Quality 3D LCD TV

AbstractWe propose the new 240Hz driving method that includes black frame insertion, LED BLU(back light unit) control and shutter glasses control to reduce crosstalk caused mainly by slow LC response and data scanning driving method. As a result, it realizes 240Hz Full HD 3D LCD TV with average crosstalk about 1% level.

P‐67: Simulation of Backlight Using Bidirectional Scattering Distribution Function

AbstractBSDF (Bidirectional Scattering Distribution Function) has been used in order to predict exact optical characteristic of BLU (Backlight Unit). BSDF implies real scattering characteristics, and measured using test equipment of Goniometer type and compared simulation results with measuring data. Simulation was performed for direct‐type LED BLU and CCFL BLU by applying BSDF for diffuser sheet, diffuser plate, and reflector. Accuracy of total flux and luminance, viewing angle, image, etc. was increased and simulation result was obtained in a short time using BSDF assuming multiple sheets as one sheet.

에노다이징 절연층과 반사컵 구조를 보유한 COB타입 LED BLU 광원구현

LED BLU(Back Light Unit), based on MCPCB(Metal Core Printed Circuit Board) with anodizing oxide dielectric layer and improved thermal dissipation property, are presented. Reflecting cups were also formed on the surface of the MCPCB such that optical coupling between neighboring chips were minimized for improving the photon extraction efficiency. LED chips were directly attached on the MCPCB by using the COB (Chip On Board) scheme.

57.2: Optical Design of Phosphor Sheet Structure in LED Backlight System

AbstractA novel LED backlight unit with a phosphor sheet is proposed. The basic structure of the phosphor sheet consists of a phosphor layer with a diffusion layer on either side of the phosphor layer. The diffusion layers can reduce the chromaticity shift due to the viewing angle and incident angle of blue light.

64.4: Smart Algorithms for Local Dimming LED Backlight

AbstractTo reduce power consumption and improve image quality including contrast ratio and color gamut, LED backlight units (BLUs) consisting of many small blocks in 2‐dimensional space are implemented. Either white‐gray‐level luminance or color is controlled by the local dimming LED BLU. However, such a BLU can induce various recognizable artifacts. A method is proposed for exact block luminance calculation along with a new algorithm to correct local dimming artifacts. A new concept of color classes has also been developed to achieve extremely wide color gamut and to minimize color related artifacts.

Enhancement of the Optical Performances for the LED Backlight Systems with a Novel Dual Lens-Cap

A novel dual-cone-shaped side-emitting lens cap for High Brightness Light Emitting Diodes (HB-LEDs) is proposed for improving brightness and high uniformity of the direct LED backlight Units (BLUs) for large-sized LCD-TVs. Combining the designed lens cap with red, green and blue (RGB) chips on a Metal Core Printed Circuit Board (MCPCB), the LED module with the proposed cap is able to provide a compact white light source with unique features such as instant color variability and lower power usage, etc. The dual-cone-shaped of the proposed lens cap is designed to emit most of the light rays to the sides, only a small portion of light upward along the optical axis of the lens, providing a uniform luminance distribution and the high brightness on the backlight. In addition, a small reflective surface in semi-circular shape is designed and placed upon the proposed LED module about 10mm, the surfaces of which are attached with reflective films to increase the level of light mixing in the larger, global reflector optical box. With the structure of the LED module well designed, the LED backlight Module would be designed for the large-sized LCDTV using the fewer number of LEDs to lead to lower power consumption. The results indeed identify the attributes of the BLU, which make it possible to achieve excellent backlight performance using a direct illumination approach from the light source of “Dual-Cone-Shaped Side- Emitting Lens Cap of LEDs.”