Thermal Characteristics of LED Light Source in Flat Panel Display Backlight System

2007 ◽  
Author(s):  
Sung Ki Kim ◽  
Joon Kang ◽  
Seo Young Kim
Keyword(s):  
Image Quality ◽  
Light Source ◽  
Light Emitting Diode ◽  
Thermal Characteristics ◽  
Temperature Limit ◽  
Wavelength Shift ◽  
Flat Panel Display ◽  
Flat Panel ◽  
Led Light ◽  
Led Backlight

Light Emitting Diode (LED) begins to be applied as backlight system in a flat panel display because of local dimming function, wide color gamut, longer lifetime and environmental-friendly feature. The performance of LED device is strongly dependent on the operating temperature, however, the operation beyond temperature limit could cause the luminosity decrease, wavelength shift and lifetime decrease including failure of electrode soldering in the package. Therefore, the thermal management in a LED backlight system is crucial to guarantee the image quality and the reliability of the display. However, narrow volume of flat panel displays cause low convective heat transfer showing non-uniform temperature distribution over the panel. It deteriorates the image quality that the inherent temperature difference over the flat panel display backlight system. The objective of present study aimed to investigate the effect of LED alignment in a direct-illuminating type backlight system. It is discussed thermal characteristics of backlights in flat panel with LED light source and evaluated performance of the heat spreading system to ensure the reliability of LED backlight system.

scholarly journals Optimal Color Lighting for Scanning Images of Flat Panel Display using Simplex Search

2018 ◽  
Vol 4 (11) ◽  
pp. 133
Author(s):  
HyungTae Kim ◽  
EungJoo Ha ◽  
KyungChan Jin ◽  
ByungWook Kim
Keyword(s):  
Image Quality ◽  
Light Source ◽  
Light Emitting Diode ◽  
Optical Filters ◽  
Flat Panel Display ◽  
Flat Panel ◽  
Light Emitting ◽  
Simplex Search ◽  
Inspection Systems ◽  
Color Control

A system for inspecting flat panel displays (FPDs) acquires scanning images using multiline charge-coupled device (CCD) cameras and industrial machine vision. Optical filters are currently installed in front of these inspection systems to obtain high-quality images. However, the combination of optical filters required is determined manually and by using empirical methods; this is referred to as passive color control. In this study, active color control is proposed for inspecting FPDs. This inspection scheme requires the scanning of images, which is achieved using a mixed color light source and a mixing algorithm. The light source utilizes high-power light emitting diodes (LEDs) of multiple colors and a communication port to dim their level. Mixed light illuminates an active-matrix organic light-emitting diode (AMOLED) panel after passing through a beam expander and after being shaped into a line beam. The image quality is then evaluated using the Tenenbaum gradient after intensity calibration of the scanning images. The dimming levels are determined using the simplex search method which maximizes the image quality. The color of the light was varied after every scan of an AMOLED panel, and the variation was iterated until the image quality approached a local maximization. The number of scans performed was less than 225, while the number of dimming level combinations was 20484. The proposed method can reduce manual tasks in setting-up inspection machines, and hence is useful for the inspection machines in FPD processes.

scholarly journals Analysis on High-Power Seaport LED Luminaire with Uniform Light Distribution Based on Optimized Lens and Heatsink

2021 ◽  
Vol 11 (9) ◽  
pp. 4035
Author(s):  
Jinsheon Kim ◽  
Jeungmo Kang ◽  
Woojin Jang
Keyword(s):  
Light Source ◽  
High Power ◽  
Heat Dissipation ◽  
Light Emitting Diode ◽  
Light Distribution ◽  
Light Sources ◽  
Led Light ◽  
High Power Led ◽  
Distribution Requirement ◽  
Lighting Application

In the case of light-emitting diode (LED) seaport luminaires, they should be designed in consideration of glare, average illuminance, and overall uniformity. Although it is possible to implement light distribution through auxiliary devices such as reflectors, it means increasing the weight and size of the luminaire, which reduces the feasibility. Considering the special environment of seaport luminaires, which are installed at a height of 30 m or more, it is necessary to reduce the weight of the device, facilitate replacement, and secure a light source with a long life. In this paper, an optimized lens design was investigated to provide uniform light distribution to meet the requirement in the seaport lighting application. Four types of lens were designed and fabricated to verify the uniform light distribution requirement for the seaport lighting application. Using numerical analysis, we optimized the lens that provides the required minimum overall uniformity for the seaport lighting application. A theoretical analysis for the heatsink structure and shape were conducted to reduce the heat from the high-power LED light sources up to 250 W. As a result of these analyses on the heat dissipation characteristics of the high-power LED light source used in the LED seaport luminaire, the heatsink with hexagonal-shape fins shows the best heat dissipation effect. Finally, a prototype LED seaport luminaire with an optimized lens and heat sink was fabricated and tested in a real seaport environment. The light distribution characteristics of this prototype LED seaport luminaire were compared with a commercial high-pressure sodium luminaire and metal halide luminaire.

Non-visual Effects of Flat Panel Display with Light Emitting Diode Backlight on Human

2013 ◽  
Vol 42 (7) ◽  
pp. 768-771
Author(s):  
宋丽妍 SONG Li-yan ◽  
李俊凯 LI Jun-kai ◽  
牟同升 MOU Tong-sheng
Keyword(s):  
Light Emitting Diode ◽  
Flat Panel Display ◽  
Flat Panel ◽  
Visual Effects ◽  
Light Emitting

1.331μm Narrow-Bandwidth Light Source Based on Polymer Micro-Blazed Grating

2008 ◽  
Author(s):  
Hairong Wang ◽  
Xianni Gao ◽  
Guoliang Sun ◽  
Yulong Zhao ◽  
Zhuangde Jiang
Keyword(s):  
Light Source ◽  
Light Emitting Diode ◽  
Low Cost ◽  
Diffraction Order ◽  
Blazed Grating ◽  
Light Emitting ◽  
Led Light ◽  
Narrow Bandwidth ◽  
Narrow Width ◽  
The Cost

In order to detect methane (CH4) accurately and reliably, this paper presents a sensor which consists of infrared diode, fixtures, blazed grating, to realize the extremely narrow-bandwidth light at wavelength of 1.331μm. Based on factors such as compatibility with the transmission characteristics of silica fiber and the cost, a LED (light-emitting diode) with center wavelength of 1.3μm is selected. The LED light is modulated as the parallel light beam. As the light is incident in a micro-blazed grating with certain angle, by diffraction and interference, the light will output the maximum light intensity of its diffraction order at 1.331 μm, which just is an absorption peak of CH4. Micro-blazed grating applied here is low cost and easy replication by various ways, which makes extreme narrow width wavelength possible. Simulation and analysis indicate the designed prototype can output 1.331μm with bandwidth from 1.32907μm to 1.332495μm. With the light source basing on light dividing system, more reliable and higher sensitive measurement of the dangerous gases such as methane and carbon monoxide (CO) can be realized.

Comparison and Research of LED Screen’s Image Quality Optimizing Technology

2011 ◽  
Vol 480-481 ◽  
pp. 1373-1377 ◽  
Author(s):  
Xiao Ming Zhao ◽  
Xiao Yuan Zhou ◽  
Sheng Chun Yuan
Keyword(s):  
Image Quality ◽  
Light Emitting Diode ◽  
Basic Principles ◽  
Central Wavelength ◽  
Light Emitting ◽  
Led Light ◽  
Display Unit

This paper compares and analyzes various common sub-pixels layouts in the outdoor LED (Light Emitting Diode) display industry. According to the basic principles of chromatics and the instructions about central wavelength of LED lamps, proposed that the ratio (2:1:1) of the red, green, blue lamps in one display unit of the 4-subpixels arrangement should be changed to 1:2:1 to improve the clarity of the screen. Besides, to solve the chaotic situation of relating technologies, the paper proposed that optimizing technologies of image quality around LED screen can be classified into two groups based on sub-pixels layouts---centralizing and dispersing evenly.

scholarly journals Investigation on optical integration between LED Mid-IR light sources and Si-based waveguides for sensing applications

2021 ◽  
Vol 2145 (1) ◽  
pp. 012056
Author(s):  
Pawaphat Jaturaphagorn ◽  
Papichaya Chaisakul ◽  
Nattaporn Chattham ◽  
Pichet Limsuwan
Keyword(s):  
Integrated Circuits ◽  
Light Source ◽  
Light Emitting Diode ◽  
Coupling Scheme ◽  
Light Sources ◽  
Optical Coupling ◽  
Led Light ◽  
Carbon Dioxide Gas ◽  
Sensing Applications ◽  
Ir Light

Abstract Research on mid-IR silicon-based waveguides has recently received strong interest. Particularly, this paper focuses on one of the critical issues in micron-scale photonic integrated circuits, which is to efficiently couple a mid-IR LED (light emitting diode) light source to an external micron-scale waveguide. The optical coupling scheme is crucial for the exploitation of LED light sources in waveguide-based spectroscopic sensing applications. This paper reports optical coupling scheme between an LED mid-IR light source and a silicon rich silicon nitride (SiN) waveguide that could enable the use of LED-based light sources. Finally, the detection limit of the investigated device for carbon dioxide gas detection is calculated.

Optical and Thermal Analysis for Polymer Light-emitting Diode as A Flat Panel Light Source

2011 ◽  
Vol 32 (8) ◽  
pp. 809-815
Author(s):  
桂宇畅 GUI Yu-chang ◽  
林昊天 LIN Hao-tian ◽  
刘艳梅 LIU Yan-mei ◽  
张剑平 Zhang Jian-ping ◽  
文尚胜 WEN Shang-sheng
Keyword(s):  
Thermal Analysis ◽  
Light Source ◽  
Light Emitting Diode ◽  
Flat Panel ◽  
Light Emitting ◽  
Panel Light ◽  
Polymer Light Emitting Diode
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