High Efficiency and Wide Color Gamut Liquid Crystal Displays

Liquid crystal display (LCD) has become ubiquitous and indispensable in our daily life. Recently, it faces strong competition from organic light emitting diode (OLED). In order to maintain a strong leader position, LCD camp has an urgent need to enrich the color performance and reduce the power consumption. This dissertation focuses on solving these two emerging and important challenges. In the first part of the dissertation we investigate the quantum dot (QD) technology to improve the both the color gamut and the light efficiency of LCD. QD emits saturated color and grants LCD the capability to reproduce color vivid images. Moreover, the QD emission spectrum can be custom designed to match to transmission band of color filters. To fully take advantage of QD\u27s unique features, we propose a systematic modelling of the LCD backlight and optimize the QD spectrum to simultaneously maximize the color gamut and light efficiency. Moreover, QD enhanced LCD demonstrates several advantages: excellent ambient contrast, negligible color shift and controllable white point. Besides three primary LCD, We also present a spatiotemporal four-primary QD enhanced LCD. The LCD\u27s color is generated partially from time domain and partially from spatial domain. As a result, this LCD mode offers 1.5× increment in spatial resolution, 2× brightness enhancement, slightly larger color gamut and mitigated LC response requirement (~4ms). It can be employed in the commercial TV to meet the challenging Energy star 6 regulation. Besides conventional LCD, we also extend the QD applications to liquid displays and smart lighting devices. The second part of this dissertation focuses on improving the LCD light efficiency. Conventional LCD system has fairly low light efficiency (4%~7%) since polarizers and color filters absorb 50% and 67% of the incoming light respectively. We propose two approaches to reduce the light loss within polarizers and color filters. The first method is a polarization preserving backlight system. It can be combined with linearly polarized light source to boost the LCD efficiency. Moreover, this polarization preserving backlight offers high polarization efficiency (~77.8%), 2.4× on-axis luminance enhancement, and no need for extra optics films. The second approach is a LCD backlight system with simultaneous color/polarization recycling. We design a novel polarizing color filter with high transmittance ( \u3e 90%), low absorption loss (~3.3%), high extinction ratio (\u3e10,000:1) and large angular tolerance (up to ±50˚). This polarizing color filter can be used in LCD system to introduce the color/polarization recycling and accordingly boost LCD efficiency by ~3 times. These two approaches open new gateway for ultra-low power LCDs. In the final session of this dissertation, we demonstrate a low power and color vivid reflective liquid crystal on silicon (LCOS) display with low viscosity liquid crystal mixture. Compared with commercial LC material, the new LC mixture offers ~4X faster response at 20oC and ~8X faster response at -20°C. This fast response LC material enables the field-sequential-color (FSC) driving for power saving. It also leads to several attractive advantages: submillisecond response time at room temperature, vivid color even at -20oC, high brightness, excellent ambient contrast ratio, and suppressed color breakup. With this material improvement, LCOS display can be promising for the emerging wearable display market

Automated Control For Electrical Appliances By Using RFID

This study features the implementation of a security system utilizing Radio Frequency Identification (RFID) which, through the basic interface provided by ASCII technology, allows interoperability with the tag (smart card). The RFID Automated Control for Electrical Appliances system is an access system that enables entry using a smart card, suitable for minimizing and reducing the electrical usage inside houses, offices and factories to ensure that only authorized personnel is allowed access

Evaluation of the color image and video processing chain and visual quality management for consumer systems

With the advent of novel digital display technologies, color processing is increasingly becoming a key aspect in consumer video applications. Today’s state-of-the-art displays require sophisticated color and image reproduction techniques in order to achieve larger screen size, higher luminance and higher resolution than ever before. However, from color science perspective, there are clearly opportunities for improvement in the color reproduction capabilities of various emerging and conventional display technologies. This research seeks to identify potential areas for improvement in color processing in a video processing chain. As part of this research, various processes involved in a typical video processing chain in consumer video applications were reviewed. Several published color and contrast enhancement algorithms were evaluated, and a novel algorithm was developed to enhance color and contrast in images and videos in an effective and coordinated manner. Further, a psychophysical technique was developed and implemented for performing visual evaluation of color image and consumer video quality. Based on the performance analysis and visual experiments involving various algorithms, guidelines were proposed for the development of an effective color and contrast enhancement method for images and video applications. It is hoped that the knowledge gained from this research will help build a better understanding of color processing and color quality management methods in consumer video

유기발광 다이오드 표시장치를 장착한 이동형 시스템의 전력 공급 최적화

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2012. 8. 장래혁.오늘날 스마트폰, 태블릿 PC 와 같은 휴대용 전자기기는 고성능의 중앙처리장치 (CPU), 대용량 메모리, 대형 화면, 고속의 무선 인터페이스 등을 탑재함에따라 전 력 소모량이 급속히 증가하여 그 전력 소모는 이미 소형의 랩탑 컴퓨터 수준에 이르고 있다. 성능과 전력 소모량의 측면에서 휴대용 전자기기와 랩탑 컴퓨터 사 이의 구분이 점차 사라지고 있음에도 배터리 및 전력 변환 회로는 기존의 설계 원칙들만을 따라 설계되고 있는 실정이다. 삼성전자의 갤럭시 탭 및 Apple 사의 iPad 등 스마트폰 및 태블릿 PC의 경우 1-cell 직렬 리튬 이온 전지를 사용하는 반 면, 랩탑 컴퓨터의 경우는 제조사에 따라 3-cell 에서 5-cell 직렬 등으로 설계되고 있다. 이는 배터리 출력 전압을 다르게 함으로써 전력 변환 효율에 영향을 준다. 전력 변환 회로의 효율 및 배터리의 수명은 입출력 전압/전류를 비롯한 동작 환경의 영향을 받는다. 휴대용 전자기기에 사용되는 각종 전자부품은 전력 소모를 줄이기 위한 다양한 기능들을 구현하고 있으며, 중앙처리장치의 동적 전압/주파 수 조절 기법 등 공급전압의 변화를 수반하는 기법 역시 다양하게 적용되고 있다. 이는 각 장치의 공급 전압 및 전류의 변화로 인한 전력 변환 회로의 효율의 변화 를 초래한다. 따라서 중앙처리장치, 디스플레이 등 주요 전력 소비 장치의 전력 절감 기법을 개발할 때에는 개별 장치의 전력 소비를 줄이는 것과 동시에 개별 장 치의 동작 행태에 대한 정확한 분석에 기반하여 배터리, 전력 변환회로의 설계가 함께이루어져야 한다. 선행 연구를 통해 배터리의 특성을 고려한 배터리 구성의 최적화 기법이 제안되었다 [1]. 중앙처리장치의 동적 전압/주파수 제어 기법에 이어 유기발광다이오드(OLED) 기반 디스플레이의 동적 구동회로 공급 전압 기법이 제안되었다 [2]. 유기발광다 이오드 디스플레이는 전력 소모 및 시야각 등 기존 액정 표시장치에 비해 여러 우수한 특성으로 인해 주목받고 있는 차세대 디스플레이 장치이다. 유기발광다 이오드 디스플레이의 적은 전력 소모량에도 불구하고 화면의 대형화 및 해상도의 고밀도화에 따라 시스템 전력 소모에서 여전히 큰 비중을 차지하고 있다. 유기발 광다이오드 디스플레이의 동적 구동회로 공급 전압 기법(OLED DVS)는 색상의 변화의 기초한 기존의 유기발광다이오드 디스플레이 전력 절감 기법과는 달리 최 소한의 이미지 왜곡만을 수반하여 대부분의 사진, 동영상 등에 적용가능한 전력 절감 기법이다. 해당 기법은 공급 전압의 변화시킬 필요가 있으며, 이를 시스템에 올바르게 통합시키기 위해서는 전력 변환 회로 및 배터리 구성에 미치는 영향을 고려해야 한다. 본 논문에서는 유기발광다이오드 디스플레이의 전력 소모와 함께 전체 시스 템 효율에 미치는 영향을 함께 고려하여 시스템을 최적화한다. 배터리 구성 역 시 기존의 설계 표준 대신 체계적인 시스템 분석에 기반한 최적화가 시도되었다. 공급전압이 조절 가능한 유기발광다이오드 디스플레이 하드웨어 및 제어기 시스 템-온-칩 (System-on-a-chip, SoC) 가 제작되었고, 그 동작 특성이 분석되었다. 기존 스마트폰 및 태블릿 PC 개발용 플랫폼의 전력 변환 효율 및 동작 특성 역시 분석 되었다. 유기발광다이오드 디스플레이의 동적 구동회로 공급 전압 기법의 동작 특성 및 스마트폰 플랫폼의 동작 특성, 배터리 특성에 대한 분석을 기반으로 시스 템 수준에서의 전력 변환 효율이 최적화되었다.Modern mobile devices such as smartphone or tablet PC are typically equipped a high-performance CPU, memory, wireless interface, and display. As a result, their power consumption is as high as a small-size laptop computer. The boundary between the mobile devices and laptop computer is becoming unclear from the perspective of the performance and power. However, their battery and related power conversion architecture are only designed according to the legacy design so far. Smartphone and tablet PCs from major vendors such as iPad from Apple or Galaxy-tab from Samsung uses 1-cell Li-ion battery. The laptop PC typically has 3-cell Li-ion battery. The output voltage of the battery affect system-level power conversion efficiency. Furthermore, traditional power conversion architecture in the mobile computing system is designed only considering the fixed condition where the system-level low-power techniques such as DVFS are becoming mandatory. Such a low-power techniques applied to the major components result in not only load demand fluctuation but also supply voltage changing. It has an effect on the battery lifetime as well as the system-level power delivery efficiency. The efficiency is affected by the operating condition including input voltage, output voltage, and output current. We should consider the operating condition of the major power consumer such as a display to enhance the system-level power delivery efficiency. Therefore, we need to design the system not only from the perspective of the power consumption but also energy storage design. The optimization of battery setup considering battery characteristics was presented in [1]. Beside the DVFS of microprocessor, a power saving technique based on the supply voltage scaling of the OLED driver circuit was recently introduced [2]. An organic light emitting diode (OLED) is a promising display device which has a lot of advantages compared with conventional LCD, but it still consumes significant amount of power consumption due to the size and resolution increasing. The OLED dynamic voltage scaling (OLED DVS) technique is the first OLED display power saving technique that induces only minimal color change to accommodate display of natural images where the existing OLED low-power techniques are based on the color change. The OLED DVS incurs supply voltage change. Therefore we need to consider the system-level power delivery efficiency and battery setup to properly integrate the DVS-enabled OLED display to the system. In this dissertation, we not only optimize the power consumption of the OLED display but also consider its effect on the whole system power efficiency. We perform the optimization of the battery setup by a systematic method instead of the legacy design rule. At first, we develop an algorithm for the OLED DVS for the still images and a histogram-based online method for the image sequence with a hardware board and a SoC. We characterize the behavior of the OLED DVS. Next, we analyze the characteristics of the smartphone and tablet-PC platforms by using the development platforms. We profile the power consumption of each components in the smartphone and power conversion efficiency of the boost converter which is used in the tablet-PC for the display devices. We optimize not only the power consuming components or the conversion system but also the energy storage system based on the battery model and system-level power delivery efficiency analysis.1 Introduction 1.1 Supply Voltage Scaling for OLED Display 1.2 Power Conversion Efficiency in MobileSystems 1.3 Research Motivation 2 Related Work 2.1 Low-Power Techniques for Display Devices 2.1.1 Light Source Control-Based Approaches 2.1.2 User Behavior-Based Approaches 2.1.3 Low-Power Techniques for Controller and Framebuffer 2.1.4 Pre-ChargingforOLED 2.1.5 ColorRemapping 2.2 Battery discharging efficiency aware low-power techniques 2.2.1 Parallel Connection 2.2.2 Constant-Current Regulator-Based Architecture 2.3 System-level power analysis techniques 3 Preliminary 38 3.1 Organic Light Emitting Diode (OLED) Display 3.1.1 OLED Cell Architecture 3.1.2 OLED Panel Architecture 3.1.3 OLED Driver Circuits 3.2 Effect of VDD scaling on driver circuits 3.2.1 VDD scaling for AM drivers 3.2.2 VDD scaling for PWM drivers 4 Supply Voltage Scaling and Image Compensation of OLED displays 4.1 Image quality and power models of OLED panels 4.2 OLED display characterization 4.3 VDD scaling and image compensation 5 OLED DVS implementation 5.1 Hardware prototype implementation 5.2 OLED DVS System-on-Chip implementation 5.3 Optimization of OLED DVS SoC 5.4 VDD transition overhead 6 Power conversion efficiency and delivery architecture in mobile Systems 6.1 Power conversion efficiency model of switching-Mode DC–DC converters 6.2 Power conversion efficiency model of linear regulator power loss model 6.3 Rate Capacity Effect of Li-ion Batteries 7 Power conversion efficiency-aware battery setup optimization with DVS- enabled OLED display 7.1 System-level power efficiency model 7.2 Power conversion efficiency analysis of smartphone platform 7.3 Power conversion efficiency for OLED power supply 7.4 Li-ion battery model 7.4.1 Battery model parameter extraction 7.5 Battery setup optimization 8 Experiments 8.1 Simulation result for OLED display with AM driver 8.2 Measurement result for OLED display with PWM driver 8.3 Design space exploration of battery setup with OLED displays 9 Conclusion 10 Future WorkDocto

Appearance-based image splitting for HDR display systems

High dynamic range displays that incorporate two optically-coupled image planes have recently been developed. This dual image plane design requires that a given HDR input image be split into two complementary standard dynamic range components that drive the coupled systems, therefore there existing image splitting issue. In this research, two types of HDR display systems (hardcopy and softcopy HDR display) are constructed to facilitate the study of HDR image splitting algorithm for building HDR displays. A new HDR image splitting algorithm which incorporates iCAM06 image appearance model is proposed, seeking to create displayed HDR images that can provide better image quality. The new algorithm has potential to improve image details perception, colorfulness and better gamut utilization. Finally, the performance of the new iCAM06-based HDR image splitting algorithm is evaluated and compared with widely spread luminance square root algorithm through psychophysical studies

Design, measurement and analysis of multimode light guides and waveguides for display systems and optical backplane interconnections

The aim of the research in this thesis was to design and model multimode lightguides for optimising visible light for liquid crystal display systems and to design, model and experimentally test infrared light propagation within polymer multimode waveguides as board-to-board interconnects for high data rate communication. Ray tracing models the behaviour of a novel LCD colour separating backlight to optimize its efficiency by establishing the optimum dimensions and position for a unique micro-mirror array within the light guide. The output efficiency increased by 38.2% compared to the case without the embedded mirror array. A novel simulation technique combined a model of liquid crystal director orientation and a non-sequential ray tracing program was used first time to compute the reflected intensity from a LCOS device for a rear projection TV system. The performance of the LCOS display was characterised by computing the contrast ratio over a ±15° viewing cone. Photolithographically manufactured embedded multimode waveguides made from acrylate Truemode® polymer are characterized by measuring the optical transmission loss of key waveguide components including. straight, bend and crossing. Design rules derived from the experimental measurement were used to optimize optical PCB (OPCB) layout. A most compact and complex optical interconnects layout up-to-date for data centres, including parallel straight waveguide sections, cascaded 90° bends and waveguide crossing other than 90° angles, was designed, tested and used in an optic-electrical demonstration platform to convey a 10.3 Gb/s data. A further new method for reducing the end facet roughness and so the coupling loss, by curing a thin layer of core material at the end of the waveguide facet to cover the roughness fluctuations, was proposed and successfully demonstrated giving the best results reported to date resulting in an improvement of 2.8 dB which was better than the results obtained by using index matching fluid