用LED实现高亮度超薄型背光源的设计方法

近年来随着LED产业的发展,LED光源在背光应用领域也在不断拓展。本文主要从LED直下式背光源的结构特点探讨,如何提高亮度和均匀性,用光学软件模拟了用大功率白光LED实现高亮度和均匀性的背光模组,用实验数据验证了最初理论结果。并对LED直下式结构模组和LED侧入式结构模组的优缺点进行了对比和全面分析,及直下式LED背光结构在背光源系统的各个领域广泛应用的必然性。     

Study on the light delivery to a transmissive‐LCD spatial light modulator used in an LED projector

Abstract— The main targeted areas of this study focused on the optical analysis and design verification of light delivery to a transmissive‐LCD spatial light modulator in LED projectors. The behavior and the distribution pattern of the LED light source, its ray path, and its secondary optical performance in the light tube were investigated. Through the use of LightTools, an optical analysis software, an optical engine structure was established to simulate the LED‐light‐source distribution at the outlet of the light tube after passing through the focus lens. Optical experiments, including a goniophotometer, and scanning illumination measurements were then used to compare the results with computer‐software simulation results to ensure rationality and accuracy of the optical simulation. By using the improved approximation method for uniformity, it was found that the most suitable tilting angle for the light tube would be between 49.2° and 49.4°. The value of the light angle for minimal light intensity deviation to occur was found to be 9°. The optimum location for the light source was found to be 1 mm within the center of the light tube and at 35 mm away from the inlet of the light tube; the effect of uniformity was observed.     

LED隧道灯最优安装方式的实验研究

目前,LED隧道灯的安装主要是在原来高压钠灯安装条件的基础上替换高压钠灯,在安装位置上没有统一的规定,导致光线得不到最大化的利用。文章通过控制变量法对高压钠灯的安装高度和角度进行了实验研究,得出LED隧道灯的最优安装方式,以便为今后长大公路隧道开展绿色照明研究提供借鉴与参考。     

提高汽车背景光大面积照明亮度一致性的光源布置

汽车背景光系统广泛应用LED光源进行照明,单颗LED近似为点光源,在较大面积照明的情况下,LED光源的布置方式在很大程度上影响了亮度的一致性.研究了LED作为背光源的照明特点,分析了LED背光源的布置对汽车背景光亮度一致性的影响,提出一种通过优化光源布置确定相邻LED间距提高汽车背景光较大面积照明亮度一致性的方法.该方...     

Optimized design of LED freeform lens for uniform circular illumination

An optimization method is proposed for designing an LED freeform lens which produces a uniform circular pattern with high energy efficiency.This method is composed of three main aspects:design of the initial guess,parameterization of the freeform surface,and construction of the merit function.The initial guess is created by solving an ordinary differential equation numerically.An approach of selecting optimization points is introduced for parameterization of the freeform surface.The merit function is constructed by use of the irradiance uniformity and the efficiency of the lens.Design examples are given,and the results show that the irradiance distribution is well controlled with a maximum uniformity(the relative standard deviation of irradiance,RSD) of 0.0122 and a maximum efficiency of 93.88%.This optimization method can be generalized to design freeform lenses with different lighting patterns or without rotational symmetry.     

Measurement of image quality for large-screen displays based on audience viewing: Overview of standardization and preliminary study on laser projection displays and LED displays

The large screens used in stadiums, shopping malls, and movie theaters typically have multiple viewers looking at them simultaneously. The quantification of these displays' image quality would require more considerations of measurements at different locations to satisfy the multiviewing condition. In this paper, we describe the practical implementation method involved in the current standardization activities. Additionally, a vantage point measurement method is studied. In the actual use case scenarios, the vantage point method is more appropriate. This method mimics the viewing behavior of audiences. The displays we measured were laser projection and LED. The method shows validity in both displays. Using the vantage point method, the experimental data show that the existing large displays may have very prominent differences in luminance and chromaticity at different viewing locations.     

A study of patent analysis of LED bicycle light by using modified DEMATEL and life span

The present study proposed a modified decision-making trial and evaluation laboratory (DEMATEL) method. This innovation method involves collecting the repeated or identically defined technical keywords of patent techniques related to light-emitting diode (LED) bicycle light to determine the ratios of the normalized numerical values of these technical keywords by using one technical domain as the primary domain and another as a variable. The values obtained are then converted to mutual influence levels on a scale of 0 to 4, replacing the conventional expert questionnaire. In this study, in accordance with the operational steps of the decision-making trial and evaluation laboratory method, a general relational influence matrix, direct and indirect relationships diagram, and values of centrality (D + R) and causality (D − R) were obtained. A causal diagram was therefore created. The causal diagram was drawn using values of (D + R) and (D − R) as the two axes and facilitated determining the levels of mutual influence between technical domains. In accordance with the proposed modified decision-making trial and evaluation laboratory method, this study collected patents related to LED bicycle light; moreover, the normalized numerical values of key technical, part/component, and function words that appeared in these patents were calculated. Furthermore, clusters of technical and part or component words were defined in accordance with the first-layer technical category. The second-layer technical categories and functional categories were subsequently defined under the first-layer technical categories to establish the technique–function matrix, thereby dividing the techniques related to LED bicycle light into seven main technical domains. This study then analyzed patent life span. Patent life span was calculated using the announcement date of related patents. Finally, this study investigated the development potential of each technical domain of LED bicycle light by conducting a combined analysis of causal diagram obtained by modified DEMATEL method, activity trend chart of techniques, and patent life spans. The proposed patent analysis method and results can serve companies and engineers as references to facilitate developing new patents.     

短距离LED可见光音频传输系统设计

基于白光LED照明和通信双重作用,构建了一种短距离白光LED可见光音频传输系统。从短距离、低功率系统考虑,分析可见光传输模型和影响因素,设计可行的可见光发射端和接收端。采用AGC电路和限幅放大电路提高系统的动态范围,保证语音信息输出稳定;采用阵列接收方式扩大接收角,提高系统灵敏度。为了实现系统噪声匹配,设计了低噪声高增益前置放大器。测试结果表明,系统实现了可见光短距离音频信息的无失真传输,验证了系统的可行性。     

大功率LED灯光动态变化控制器设计

设计了一套能同时控制红色、绿色、蓝色3路30 W功率LED灯的控制器,采用Microchip公司的dsPIC30F2023处理器对LED灯电流进行闭环控制,使其按照给定要求变化,从而使红色、绿色、蓝色LED灯发出预定要求强度的光,组合成非常美丽的光线。     

白光LED煤矿工作面可见光通信调制技术研究

介绍了煤矿工作面可见光通信系统总体结构;研究了煤矿工作面可见光通信关键技术,包括载波调制技术、调制驱动电路设计以及调制带宽,得出兼顾带宽和发光效率的白光LED是理想的可见光通信系统光源。     

Implementation of an LED backlight for avionics displays

Abstract— The replacement of conventional light sources used to backlight displays with LEDs is very attractive in avionics. Today's LED technology provides devices suitable to implement display backlight sources but specific requirements need to be satisfied for avionics displays. This paper covers the development of an innovative LED backlight dedicated to avionics displays, realized in a new box geometry in order to generate more than 10,000 cd/m² on a 6 × 5‐in. active area using less than 28 W of power.     

Improvement of extraction efficiency for GaN-based light emitting diodes

A simple, low cost method for mass production to enhance the light extraction efficiency of GaN-related LEDs was proposed. With appropriate process parameters, the nature lithography of nanosphere can be used to fabricate two-dimensional nanostructures, including the nanomesh ZnO layer, photonic crystal (PhC) patterned p-GaN, and patterned sapphire substrates. Based on preliminary results, the extraction efficiencies of LEDs with these nanostructures can thus be improved and the nature lithography is demons...     

A common type of commercially available LED light source allows for colour discrimination performance at a level comparable to halogen lighting

Abstract

As light sources based on light emitting diodes (LED) are increasingly used to replace classic tungsten-based light sources in household lighting applications, possible impairments of colour perception under those light sources due to a different spectral power distribution become a major concern. The Colour Rendering Index (CRI) which is the only measure available to the end user is controversial and does not represent a comprehensive measure of colour perception. Aspects of colour perception disregarded by the CRI such as colour discrimination have to be taken into account as well. Therefore, we evaluated colour discrimination performance under a commercially available phosphor-converted LED light source from a popular brand (OSRAM) in comparison to a classic tungsten-based halogen light source. Colour discrimination performance was not affected by the type of light source, indicating that the phosphor-converted LED light source enables colour discrimination performance comparable to that of halogen lighting despite being associated with a lower CRI.

Practitioner summary: Considering the increasing use of energy efficient light sources, we compared colour discrimination under a common type of phosphor-converted LED and under traditional halogen lighting. Colour discrimination performance was comparable in both lighting conditions, indicating that the phosphor-converted LED can replace halogen lighting without sacrificing colour discrimination for energy efficiency.

Abbreviations: LED: light emitting diode; CRI: colour rendering index; CCT: correlated colour temperature; CIE: commission internationale de l’éclairage; FMHT: Farnsworth-Munsell 100-Hue Test; lm: lumen; lx: lux, lumen/m^2; W: watt; nm: nanometer; K: kelvin     

Analysis and design of light emitting diodes for optoelectronic applications

This paper presents detailed analysis and design of light-emitting diodes for optoelectronic applications. Both internal and external efficiencies are investigated taking into account the nonradiative recombination process and the total internal reflection. The dependency of the LED output power on the efficiency and double pass parasitic absorption is studied. Effect of the temperature variation on the LED performance is also studied. A complete design of an encapsulated LED operating at 1.55 m has been investigated. The design illustrates layer structures and thickness, material compositions, and index of refraction. The results show that decreasing the radiation recombination time increases the quantum efficiency, The quantum efficiency increases from 15% to 70% as the radiative recombination time reduced from 0.5 s to 0.05 s. It is also shown that increasing the width of the active region increases the output power.     

Characterization of light extraction efficiency for WOLEDS with light‐out‐coupling layer

We studied the light extraction efficiencies of white organic light‐emitting diodes with a light‐out‐coupling layer by simulations and experiments. The light extraction efficiencies estimated by the simulation were confirmed to agree well with those measured by the experiments. Moreover, we successfully obtained the high light extraction efficiency (η_OC) of 69%.