关于LED的外文文献和中文译文
【推荐】大屏幕显示系统LED的发展外文文献翻译
【word版本下载后可任意编辑】The research of the large screen display system'sLed developmentAlong with computer technology's high speed development, LED (Light Emitting Diode) the screen display system takes after the television, the broadcast, the newspaper, the magazine “the fifth big media” marches into the social life fast each aspect. Its collection microelectronic technology, the computer technology, the information processing and management technology in a body, may the information through the writing, the design, the animation and the video frequency four forms demonstrates. With media and so on bank of television monitors, magnetism vane compares, the LED large screen display system has the design to be artistic, the color is sharp; The design, the color change are rich, are fast; The low power loss, the long life, the use cost low, work stably reliable and so on characteristics. It demonstrated the chart article angle of view is big, the apparent distance is far, thus has widely applied in the large-scale square, the commercial advertizing, the sports complexes, the information dissemination, the news issue, the securities trading; It also applies in the industrial control and the industry reassignment system, is advantageous each kind of parameter, the alarm point, the technical process demonstrates clearly perfect, may satisfy the different environment the need. The LED display monitor is one kind of use computer and the complex digital signal processing electron advertisements propaganda screen. Its screen body part by the microprocessor (is mainly monolithic integrated circuit) and the driving circuit control movement, demonstrated the image or the writing obtain by the computer edition software editor. Because the LED display monitor this kind of new generation information graphic display device has the demonstration design to be stable, the power loss is low, life long and so on characteristics, moreover it synthesized each kind of information graphic display device's strong point, and has overcome own insufficiency, because specially a display monitor may demonstrate that the different content, the display mode is rich. Therefore in the public area, it has the intense advertisements propaganda and the information transmission effect, already in the solid demonstrated day by day occupies the dominant position. The LED display monitor's prospects for development are extremely broad, at present toward thehigh luminance, a higher weather fastness, the higher luminous density, the higher illumination uniformity, the reliability, the panchromatic direction is developing. Is composed of the different material's semiconductor can send out the different color the LED crystal spot. At present what applies is broadest is red, the green, yellow LED. But the blue color and the pure green LED development had already achieved the practical stage.LED display monitor's classificationLED display monitor's classified LED display monitor is many kinds of technical synthesis application product, involves photoelectronics, the semiconductor device, the digit electronic circuit, the large scale integrated circuit, the monolithic integrated circuit and the microcomputer and so on each aspect, both has the hardware and to have software. After the LED display monitor is takes the broadcast, the television, the newspaper, the magazine another new communication media. At present the LED display monitor basis uses the place to be different, may divide into the outdoor screen and the indoor screen two kinds, its main difference is photo tube's illumination brightness is different. But acts according to the content which demonstrated different also to be possible to divide into the image screen and the writing screen two kinds, the image screen may the display image as well as multimedia, but writing screen main demonstration writing or simple fixed image. Display image's multimedia outdoor screens are the investment huge (reaches as high as several millions) the large-scale upscale equipment, main application in large-scale public place, image project and some important places. The LED display monitor's application involves to social economy many domains, already spread the transportation, the negotiable securities, the telecommunication, the advertisement, the propaganda and so on each aspect.LED display monitor's trend of developmentAt present the LED display monitor's demonstration to the high luminance, a higher weather fastness, the higher illumination uniformity, a higher reliability, the panchromatic, the multimedia directions develops, system's movement, the operation and the maintenance also to the integration, the network, the intellectualized direction develop. The 21st century's display technology will be the panel display time, the LED display monitor takes one of panel display leadership products to have a bigger development.1. since the high luminance, entire color blue color and the green superelevation brightness LED product has appeared, the cost reduces fast year by year, causes the LED entire colored display monitor product cost to drop, the promoted speed speeds up. At the same time, along with control technology's development and the LED display monitor body stable enhancement, the entire colored LED display monitor's brightness, the color, white balanced achieves the quite ideal effect, definitely may satisfy the outdoors all-weather environmental condition request, moreover the image is clearer, is more exquisite, is sharper.2. after standardization, standardized material, technology mature and market price basic balanced, the LED display monitor's standardization and the standardization will become a tendency which the LED display monitor develops. In recent years industry in development, after several price recedes the adjustment achieves basically balanced, the product quality, the system reliable and so on will become the main competition factor, this had the high request to the LED display monitor's standardization and the standardization. Profession standard and standard system's formation, IS09000 series standard application, causes the LED display monitor profession the development tends the order.3. the product mix diversification along with the informationization society's formation, the information field is even more widespread, the LED display monitor's application prospect is broader. It is estimated that large-scale or the ultra-large LED display monitor will have the change for the mainstream product's aspect, will suit can have in the service industry characteristic and the specialized request small LED display monitor enhances greatly, will be richer face the information service domain's LED display monitor product class and the variety system, the part potential market demand and the application domain will have the breakthrough, like the mass transit, the parking lot, the dining, the hospital and so on comprehension service aspect's information display monitor demand will have a bigger enhancement.Involves the mentality and the principle of workThis system basis classics' circuit design mentality, uses the design method from bottom to top, from the display panel to the actuation board, arrives at the control panel again, carries on the hardware programming, after debugging successfully, receives a telegram the source plate, finally completes the data transmission board and PC machine connects, carries on the PC software programming, completes the demonstration data the production,the extraction, processing, the transmission as well as the demonstration effect real-time control. Each module uses 8 LED lattices to lighten each line by the line scan form red, green, the traffic light, the demonstration writing and the image. The LED lattice's actuation, the decoding, the lock save and so on to be responsible by control panel's digital circuit. Its data reads by the monolithic integrated circuit from the memory, simultaneously the monolithic integrated circuit uses the interrupt mode, carries on the two-way communication through the RS-232 data line and PC machine, from the PC machine gain order or the data, and carries out the movement or the stored datum according to the order. Not only but PC machine carries on many machine serial port correspondences with many monolithic integrated circuits, but must be responsible for the writing input and the typesetting, the production lattice data or the order character, realize the man-machine interaction function.Principle of work this article designs the large-scale LED display monitor becomes by the double primary color lattice LED combination, uses the line-by-line scanning the display mode to demonstrate red, green, the yellow three kind of color random lattice information. The display module uses the line-by-line scanning demonstration the way, its control system take monolithic integrated circuit AT89C52 as a core, uses 74HC154 memories to take the data-carrier storage, actuates 8*8 using latch 74HC595 and 8 group of line driver 2083The LED display module, simultaneously opens the serial port interrupt and superior PC machine carries on many machine correspondences. Through realizes display monitor's many kinds of animation pattern to the monolithic integrated circuit programming to demonstrate: Rolls the screen toward left, rolls the screen toward right, rolls the screen upwardly, rolls the screen downward, on rolls the screen toward left, on rolls the screen toward right, to the Zola curtain, pulls the curtain toward right, pulls the curtain upwardly, pulls the curtain downward, to the right lateral, lightens in turn from left to right, from among to two nearby, lightens in turn. Animation speed adjustable: Divides into 100 grades, lowest is 1 fast, highest is 100 fast. The pattern color is diverse: The background achromatic color, the writing red/green/yellow, the background is red, the writing does not have/the yellow/green, the background green, the writing does not have/yellow/red, the background yellow, the writing does not have/the red/green. Moreover, but also increased several dozens kind of neon light effect animation. The PC machine on display control software may realize functions and so on Chinese character input, typeface choice, words change, and after carrying on the data processing, may in left side simulatethe demonstration whole effect, simultaneously “sees namely obtained” demonstration in underneath preview region. Moreover, this control software also has additional functions and so on text designation, mouse localization, coordinate tracing, time date. PC machine realizes through the RS-232 connection with the demonstration part monolithic integrated circuit's correspondence, interrupts the real-time receive and the transmission data message using the monolithic integrated circuit serial port. Has also given dual attention to monolithic integrated circuit's antigambling ability in the system design, enhanced the systems operation reliability effectively.Shines the second-level tube characteristicThe light emitter diode (light emitting diode, LED), is one kind turns the electrical energy the energy of light the special component, when the electric current achieves the threshold current, the light emitter diode breakover, along with electric current passing, produces the visible light. Light emitter diode's structure mainly ties the chip, the electrode and the optical system constitution by PN. After PN ties performs the direct voltage, P area's hole injection to the N area, N area's electron-injection to the P area, the electron which and the hole meet, pours into after mutually namely produces compound, these minority carriers injection which ties in PN produce the radiation with compound to shine. It is the original radiation illumination, does not need the high injection current to have the granule number reverse distribution, also does not need the optical resonator, the launch right and wrong coherent light. Describes the LED characteristic to have many parameters, between these parameter's relations present misalignment. Therefore, describes these relations with the characteristic curve, has the use value in the project application.LED component's actuationMay know from the LED component's illumination mechanism, when exerts the direct voltage to the LED component, winds through component's forward current to cause its illumination. Therefore the LED actuation is must make its PN knot to be in the forward bias, simultaneously to control its luminous intensity, but must solve the forward current adjustment problem. The concrete drive type has [9] and so on direct-current actuation, constant flow actuation, pulse actuation and scanning actuation, in this system LED component's actuation for scanning actuation.1. direct-current actuation. The direct-current actuation is the simple the actuation。
关于LED的外文文献和中文译文
多个LED发光装置的新型采集系统作为光源的一种，发光二极管（LED）有很多优点。
LED集成度更高，颜色种类多，使用寿命更长，而且工作电压较低。
但是，它仍有一个非常大的缺陷：一只LED的光照强度还是比较低。
这个缺点导致显示屏上的光通量不会很高。
但是无论如何，LED还是以其出色的性能在低电压装置中普遍应用。
因此，利用此系统采集多个LED的光，集成为更高强度的照明装置。
本设计提出三种采集系统，来实现增强光强的功能。
效率最好的一种采集系统可以达到96%。
同时，还分析了本系统的制造误差以及预算。
1 简介利用传统的光源来设计一个便携式探照灯，尺寸和能耗会很大。
而利用LED 来设计将会避免这些问题。
LED有很多优点：节能、体积较小、使用寿命长（约100,103小时）等，尤其是LED的光很适合环境工作。
Carel Zeiss和Philips打算用LED光源设计两种便携式探照灯。
尽管LED有诸多优点，可以让他们设计出的探照灯更加便携和小巧，但是由于光学元件的转换效率问题，导致系统有很多困难。
解决这个困难将是本文研究的重点。
通常，用一种合成非线性集中器（CPC）来减小分散度。
但是，这种传统的CPC采集效率仅为72%，必须要改善采集效率来提高光的利用率。
本文中将解决分散度和采集效率两个问题。
为实现这个目标，设计了三种不同的采集系统，以提高效率，下面逐一介绍。
2 仿真部分利用光学仿真软件和标签查找模块（BRO），来设计并分析采集系统的性能。
LED光源部分来自Osram-Opical半导体。
远程LED光源是一种Lambertian模式，LED的规格见表1。
在采集系统的底部有四个LED。
系统各个LED之间的位置关系如图1。
通光部分为2.1×2.1mm2，孔径3.26mm。
LED阵列对称的分布于系统的底部。
采集系统的第一个光学元件为均质器。
这个均质器的受光角度是12.5°。
因此，这个系统就是要把LED的受光角度的范围控制在±60°到±12.5°之间。
LED点阵的外文翻译---纳米结构InGaN发光Diodesfor固态照明
（要求翻译与毕业设计（论文）相关的外文文献两篇，且3000单词以上/ 篇，将译文附在原文之后）第一篇：[ 所译外文资料：①作者：Taeil Jung②书名（或论文题目）：Nano-structured InGaN Light-Emitting Diodesfor Solid-State Lighting③出版社（或刊物名称或可获得地址）：All Rights Reserved.④出版时间（或卷期号）：2009.⑤所译起止页码：Nano-structured InGaN Light-Emitting Diodesfor Solid-State LightingSolid-state lighting can potentially reduce the electricity consumption by 25%. It requires high efficiency light-emitting diodes across the visible spectrum. GaN and related materials have direct band gap across the entire visible spectrum and are ideal for future solid-state lighting applications. However, materials defects, polarization charges, and total internal reflection have thus far limited the efficiencies of InGaN LEDs, in particular InGaN LEDs in the green/yellow wavelength range, which are critical in achieving highly efficient LED luminaries with an excellent color-rendering indexIn this Thesis, we have developed and demonstrated that novel in situ nanostructured GaN processes in MOCVD are effective in improving the efficiencies of InGaN LEDs. InGaN LEDs grown on quasi-planar semi-polar GaN templates were proven to exhibit three times higher internal quantum efficiencies and negligible quantum confined Stark effect using selective area epitaxy. InGaN LEDs grown on nanostructured semi-polar GaN templates are also effective to improve the internal quantum efficiency by 31%. The same in situ processes are also effective in reducing the defect density by an order of magnitude and increasing the photon extraction efficiency as a factor of two.The in situ processes include in situ silane treatment and high temperature overgrowth. Both processes require only standard MOCVD tools and hence are cost effective and suitable for mass-production. In situ silane treatment treatsc-plane GaN samples with silane under ammonia environment, generating nano-scale truncated cone structures with up to 200 nm scale. These truncated cone structures can be subsequently transformed into pyramidal nanostructures comprising of only (10-11) and (11-22) semipolar planes using high temperature overgrowth. These processes were applied to both InGaN active region and the LED surface to improve the internal quantum efficiency and the photon extraction efficiency, respectively. Extensive materials, device, and optical characterizations have been carried out in this research.1.1 Gallium Nitride Materials for Optoelectronic ApplicationsGallium nitride based materials, including GaN, AlN, InN, and their alloys, are excellent candidates for short-wavelength optoelectronic applications. Their direct bandgaps extend from ultraviolet to near-infrared. In addition, they exhibit high mechanical and thermal stabilities compared to other III-Vsemi-conductors, making them especially suitable for high-power andhigh-temperature operations. In recent years, breakthroughs in p-type doping and defect reduction have led to the commercialization of GaN based laser diodes, light-emitting diodes (LEDs), high electron mobility transistors (HEMT) and hydrogen detectors. Despite these advances, many technological challenges such as green gap and substrate growths still remain.Perhaps one of the most important applications for GaN based materials is solidstate lighting (SSL). Worldwide, lighting constitutes 20% of electricity consumption while its efficiency is much lower than 25%. In contrast, efficiency of space heating has exceeded 90%. To this end, the development of highly efficient and reliable LEDs for solid-state lighting has been very active in both industry and academia in the past few years. It is projected by the US Department of Energy that by 2015, if successful, solidstate lighting can reduce the overall electricity consumption by 25%.Unlike GaAs and InP based semi-conductors, GaN based materials have suffered from a high density of defects due to very limited availability of lattice-matched GaN substrates. Up to now, most GaN based optoelectronic devices have been fabricated using hetero-epitaxy on foreign substrates such as sapphire (Al2O3), silicon carbide (SiC), and aluminum nitride (AlN), and in a very small percentage on silicon. Because of large lattice mismatch, GaN grown on these substrates often exhibits a high density of threading dislocations, typically on the order of 108 – 1010 /cm2. These defects are still one of the major limiting factors for the performance of GaN based optoelectronic devices, acting as non-radiative recombination and scattering centers. Achievement of lower defect density would also improve device reliability, resulting in a longer lifetime. Various defect reduction approaches, such as epitaxial lateral over-growth (ELOG), have been demonstrated and some of the details will be discussed in Chap.1.3.1. As part of this thesis, we have explored a novel approach to using nano-structured GaN to effectively lower the threading dislocation density.Among various epitaxial techniques that have been developed for GaN based materials, metal-organic chemical vapor deposition (MOCVD) is the leading technology. The typical growth temperature for GaN materials is around 1000 to 1200°C. This high growth temperature is necessary to improve the crystal quality and is a result of low cracking efficiency of the nitrogen source, ammonia (NH3), at a low temperature. In Chapter 2, I will summarize my contributions to successfully ramp up an MOCVD tool for the epitaxial growth of GaN LEDs for this research.1.2 InGaN LEDs for Solid-State LightingThe basic component for SSL is a white-light LED. As shown in Figure 1-1, itcan be achieved by mixing various color components, which can be generated either from the direct output of individual LEDs or from color-conversion materials, such as phosphor. To date, commercially available white-light LEDs usually consist of a blue emitter and a yellow phosphor plate. It has been shown that InGaN based blue LEDs could achieve external quantum efficiency in excess of 70% [1, 2]. However, this di-chromatic configuration typically has a poor color rendering index due to the lack of green and red components. The phosphor conversion process also limits the overall luminous efficiency due to energy loss during downconversion. To achieve luminous efficiency in excess of 200 lm/W and a color rendering index (CRI) in excess of 90, which is required for general illumination, a further improvement in blue LED efficiency and the use of tetra-chromatic configuration (blue + green + yellow + red) is necessary [3].* Unfortunately, the efficiency of both InGaN and AlInGaP LEDs decreases significantly in the green-yellow (500 - 580 nm) range. This efficiency gap is also known as “green gap”. Because AlInGaP materials have indirect bandgaps in this wavelength range, to achieve high-efficiency SSL, it is crucial to significantly improve the luminousNote that a trichromatic (e.g. blue + green + red) source cannot achieve a CRI > 90. efficiency of green and yellow InGaN LEDs. In this thesis, we will address these challenges using nano-structured GaN.Figure 1-1. Illustration of various potential white-light LEDs configurations (after Ref. [4]).1.3Limiting Factors for InGaN LEDs EfficiencyTo date, the efficiencies of InGaN LEDs are still limited by materials defects, polarization charges, and photon trapping. In this Section, we will briefly review the state of theart and overview how this research helps address these limitations.1.3.1 Materials DefectsAs mentioned before, the high defect density in GaN based materials grown on foreignsubstrates increases the non-radiative recombination rate and lowers the radiative efficiency. To date, several techniques have been demonstrated to improve the crystal quality and reduce the threading dislocation (TD) density of the GaN layer. Substrate pretreatmentat the growth temperature in an ammonia environment, also known as nitridation [5-7], has been shown to be critical for high quality GaN epilayers. The TD density of a typical GaN layer grown on c-plane sapphire substrate can be reduced to 108/cm2 [8] by employing the combination of a low temperature (LT; 450 - 600 °C)nucleation layer (NL) and a short annealing at the growth temperature to change the phase of the as-grown NL from cubic to hexagonal [9-11]. As will be discussed in Chapter 2, careful optimization of these low temperature growth sequences can significantly alter the subsequent GaN template growth. To this end, a home-made optical in situ monitoring tool (reflectometry) was established and will be discussed extensively in Chapter 2.In addition low temperature buffer growth, epitaxial lateral overgrowth (ELOG) which is a variation of selective area epitaxy (SAE) has been introduced [12, 13] to further lower the TD density by an order of magnitude to below 107/cm2. Variations of ELOG including pendeo- (from the Latin : hang on or suspended from) epitaxy (PE) [14] and multi-step ELOG are also effective to further reduce the TD density. Additional techniques such as TiN nano-porous network [15] and anodic aluminum oxide nano-mask [16] have also been proposed and demonstrated. All these methods, however, require ex situ processing and hence will add complexity and cost to the manufacturing. In this thesis, we will explore and generalize an in situ silane treatment approach to effectively lowering the TD density by an order of magnitude.1.3.2 Polarization ChargesDue to the non-cubic symmetry of GaN materials, compressively-strained active regions in InGaN LEDs exhibit both spontaneous and piezoelectric polarization charges. These polarization charges induce a strong internal electric field (IEF), typically on the order of MV/cm, in the active region, resulting in both efficiency droop at a high injection current density and the decrease of radiative efficiency with an increasing emission wavelength. The IEF can separate electrons from holes and increase electron leakage, resulting in low internal quantum efficiency (IQE) and efficiency droop [17], respectively. The suppression of the IEF, which is expected to increase IQE and the current density at which efficiency droop occurs, can be achieved by reducing the lattice mismatch in hetero-structures or growing them on semi-polar (e.g. {10-11} and {11-22}) and non-polar (e.g. a-plane and m-plane) surfaces. Because indium incorporation is more difficult on non-polar planes than on semi-polar planes, it is more advantageous to fabricate long-wavelength green-yellow LEDs on semi-polar planes to suppress the IEF.At least three approaches to fabricating semi-polar InGaN LEDs have been reported thus far. These include the growth of a GaN epilayer on spinel substrates [18], on bulk GaN substrates [19-27], and on the sidewalls of pyramidal or ridge GaN structures created on planar polar GaN surfaces using SAE [28-35]. GaN grown on spinel substrates have so far exhibited a high density of threading dislocations and stacking faults, thereby compromising the potential improvement of efficiency from the lowering of IEF. The use of bulk semi-polar GaN substrates has demonstrated the advantage of a lower IEF for the enhanced efficiency of green and yellow LEDs [25, 26]. However, limitations such as prohibitively high wafer cost and small substrate size need to be resolved before this approach can become more practical. On the other hand, the SAE technique can create semi-polar planes on polar GaN surfaces.High quality polar GaN films have been fabricated from a variety of substrates including sapphire, 6H-SiC, and bulk GaN by MOCVD. Using growth rate anisotropy and three-dimensional growth, different semi-polar and non-polar GaN planes can be generated on c-plane GaN [13]. In Chapter 3, we will show that high quality InGaN multiple quantum wells (MQWs) which exhibit IQE as large as a factor of three compared to polar MQWs can be grown on pyramidal GaN microstructures. This approach, however, requires ex situ patterning processes and does not easily produce a planar structure for electrical contacts. In this thesis, a new semi-polar LED structure is investigated, which is enabled by a novel epitaxial nanostructure, namely the nanostructured semi-polar (NSSP) GaN, which can be fabricated directly on c-plane GaN but without the issues of the SAE technique mentioned above [36]. NSSP GaN also eliminates the issues of excessive defects for GaN grown on spinel substrates and lowers the cost of using bulk semi-polar GaN substrates. As we will show later, the surface of NSSP GaN consists of two different semi-polar planes: (10-11) and (11-22). Therefore it is expected that InGaN active regions fabricated on NSSP GaN can exhibit a low IEF, and hence much improved IQE.1.3.3 Photon ExtractionAfter photons are generated from the active region in LEDs, they need to escape the device in order to be useful. When light travels from a medium with a higher refractive index to a medium with a lower refractive index, total internal reflection (TIR) occurs at the interface. In InGaN LEDs, photons experiencing TIR at LED surfaces can be re-absorbed by the active region or trapped in the device due to a wave-guiding effect as shown in Figure 1-2. In a simple InGaN LED, only 4% of photons generated from the active region can escape from each device surface. It has been shown that surface textures on LED surfaces can greatly reduce TIR and improve photon extraction efficiency as illustrated in Figure 1-2. To date, many surface texturing techniques such as photonic crystal structures [37] and photo-electrochemical etching of GaN surfaces [38] have been introduced. Notably, the photo-electrochemical etching of nitrogen-terminated GaN surface has been successfully implemented into commercial blue LEDs [2]. However, these approaches all require additional ex situ patterning processes which add significant costs.In this thesis, we investigate an in situ process to fabricate nano-structured GaN surfaces on LEDs which effectively improves the photon extraction efficiency. Figure 1-2. Light traveling within waveguides (left) with a smooth interface and (right) with a rough interface (after [39]).1.4 Organization of the ThesisThe objective of this thesis is to investigate cost-effective nanofabrication techniques that can significantly improve the efficiency of the state-of-the-art InGaN LEDs in both blue and green/yellow ranges for high performance solid-state lighting. The organization of this thesis is as follows.In Chapter 2, a summary of the MOCVD techniques for InGaN LEDs is given. In Chapter 3, we study the dependence of InGaN LED IQE on {10-11} semi-polar planes using SAE. In Chapter 4, fabrication and characterization of novel andcost-effective nano-structured GaN templates will be described. Using in situ silane treatment (ISST) and high temperature overgrowth (HTO), the formation of nano-scale inverted cone structures and nano-structured semi-polar (NSSP) templates has been obtained. In Chapter 5, we study InGaN semi-polar LEDs based on NSSP templates. An improvement of internal quantum efficiency is demonstrated.A green semi-polar InGaN LED grown on a c-plane substrate is also demonstrated. In Chapter 6, current spreading in NSSP InGaN LEDs will be discussed. In Chapter 7, the application of ISST for theimprovement of photon extraction efficiency of an InGaN LED will be discussed. In Chapter 8, we will summarize and make suggestions for future work.2.1 Gallium Nitride GrowthAs mentioned in the Introduction, gallium nitride (GaN) and related alloys are excellent candidates for future solid-state lighting. To date, III-nitride epitaxial growth has been limited by the lack of sufficiently large single crystal substrate for homoepitaxial growth. Therefore, the growth of GaN and related materials has been largely based on hetero-epitaxy using hydride vapor phase epitaxy (HVPE), metal organic chemical vapor deposition (MOCVD), and molecular beam epitaxy (MBE). Among these techniques, MOCVD is the leading technology due to the advantages on material quality, scalability, and cost [40]. The material quality of GaN grown by MOCVD has been excellent owing to its relatively high growth temperature (1000 - 1200°C) [41, 42].To date, various substrate materials including sapphire (Al2O3), silicon carbide (SiC), and silicon have been studied for GaN growth (Table 2-1). Although GaN substrates have been recently introduced in markets through bulk material growth on foreign substrates using HVPE and laser cutting along specific crystal planes, the cost has been prohibitively high. On the other hand, GaN grown on c-plane (0001) sapphire substrate exhibits stable growth over a wide range of growth conditions despite high dislocation density at the interface between thesubstrate and epitaxial layer. In this research, I have helped ramping up an MOCVD system together with Dr. Hongbo Yu. In this Chapter, I will summarize the MOCVD technologies and defect reduction strategies for InGaN light-emitting diodes (LEDs) epitaxy that will be used throughout this Thesis.2.1.1 GaN Growth Using MOCVDDue to a large lattice mismatch between GaN and sapphire, it is important to contain the defects near the GaN/sapphire interface such that the defect density can be minimized in the device region. Such optimization is achieved using in situ reflectometry [44, 45]. A home-made reflectometry system shown in Figure 2-1 was established in our 3 x 2” Thomas-Swan Close-Coupled Showerhead (CCS) MOCVD system. White light is reflected from the sample surface and monitored by a spectrometer during the growth. The reflectivity is sensitive to both the surface morphology and the epitaxial layer structure.Figure 2-1. Illustration of a home-made in situ reflectometry system integrated into the MOCVD system.Figure 2-2. Typical growth conditions for GaN templates used in this research.Typical growth conditions for GaN templates used in this research are summarized in Figure 2-2 and Table 2-2. Unless otherwise mentioned, c-plane sapphire substrates were used. The five steps outlined in Table 2-2, including high temperature (HT) cleaning, nitridation, low temperature (LT) nucleation, annealing of LT nucleation layer, and HT GaN growth, are crucial for high quality GaN epilayer.Figure 2-3 and Table 2-3 show the corresponding in situ reflectometry signal.In the following, we will describe how the reflectometry signal can be used to optimize the GaN template growth. Unless otherwise mentioned, we will refer to the reflectometry signal shown in Figure 2-3.Figure 2-3. In situ reflectometry trace of GaN template growth (Sample ID : UM-S07- 254). The highlighted areas correspond to important sub-steps during the epitaxy.2.1.1.1 High Temperature CleaningInitially, as the sample temperature is ramped up, the reflectivity increases due to the increase of the refractive index of the sample. Kim et al. has thoroughly studied the effect of initial thermal cleaning on the sapphire substrate andexperimentally demonstrated that this thermal treatment can effectively reduce the surface roughness of the substrate [46]. Generally, the flat surface is preferred for the GaN nuclei to be formed uniformly, which is critical to the crystal quality of the final GaN epilayer. The specific condition for the HT cleaning should be optimized by examining the treatment temperature and time. In our GaN growth, the optimal treatment temperature and time were set to be 1075 °C and 5 minutes, respectively. Moreover, HT surface annealing can effectively eliminate surface moisture.2.1.1.2 NitridationNitridation [5, 7] is the process of NH3 preflow under hydrogen (H2) ambient to prepare the surface for growth. During nitridation, NH3 reacts with the surface oxygen atoms on the sapphire substrate. Due to the replacement of the oxygen atoms by the nitrogen atoms and the diffusion of the nitrogen atoms into a certain depth, the exposed surface becomes a smooth amorphous state. Because this change of surface morphology is on the order of tens of angstrom, the corresponding reflectivity change is not significant. It has been shown that with a proper nitridation condition, GaN epilayers with lower dislocation density and better electrical and optical properties can be achieved [7]. However, as mentioned above, suitable combination of reactor conditions such as temperature, treatment time, and NH3 flow rate must be considered. In our GaN growth, the nitridation was optimized at 530 °C for a total of 210 seconds under 3 slm of NH3 flow.2.1.1.3 Low Temperature NucleationAs mentioned in Section 1.3.1, several approaches have been introduced to reduce the threading dislocation (TD) density in growing the GaN template. Specifically, the use of low temperature nucleation layer (LT NL) has been shown to be simple yet effective. A threading dislocation density as low as 108/cm2 has been reported [8].As GaN is nucleated on sapphire, the cubic phase islands are first formed at a temperature of 450 - 600 °C. These islands are subsequently transformed into the wurtzite phase [8]. The increase of the reflectivity during the LT NL growth is attributed to the increase of reflection from the flat top surfaces of nuclei. Basically, we know that the reflection from GaN is about twice stronger than that from sapphire due to the difference in refractive indices. As the islands become denser (i.e. the growth time of LT NL becomes longer), total reflection from the top surface of nuclei becomes up to 200% of reflection from sapphire substrate assuming that the entire surface is covered by GaN islands. Even though the islands are not coalesced completely to form a crystalline layer, this is still possible because the distances between the adjacent islands are too small compared to the optical wavelength. Once the reflectance exceeds twice that of the sapphire (as shown in Figure 2-3), the islands continue to coalesce further, which results in larger GaN grains and a thicker NL. Here, the size of the nucleation islands and the thickness of the NL are critical to obtain high quality GaN epilayer. To show that, we have compared a series of GaN templates with different NL conditions. All conditions were kept the same† except the growth time of the LT NL was varied,resulting in different LT NL thicknesses. The thickness of the LT NL was extrapolated by analyzing the reflectometry data as the reflection ratio at the end of LT NL growth to the sapphire substrate (RLT NL / RSapphire). The qualities of the GaN templates were characterized using photoluminescence (PL) and x-ray diffraction (XRD). From these results, the best GaN template quality can be obtained when RLT NL / RSapphire is around 2.6 which corresponds to a 40nm thick NL, at the given growth conditions.† LT NL growth temperature = 530°C, V/III = 9140, LT NL annealing time = 420 seconds, HT GaN growth temperature = 1040°C, V/III = 1230, growth time = 4300 seconds.Figure 2-4. The comparison of GaN template qualities with respect to the reflection ratio between the LT NL surface and the sapphire substrate.2.1.1.4 Annealing of Low Temperature Nucleation LayerIn GaN hetero-epitaxy with a large lattice mismatch, the initial growth on the surface follows the Volmer Weber model [47], i.e. GaN island growth dominates. In order to obtain smooth GaN templates, these islands need to be transformed into the layer-by-layer growth mode using an NL annealing process. During annealing, the substrate temperature is gradually increased up to around 1030 - 1050 °C under NH3 overpressure. Temperature ramping rate, reactor pressure, and NH3 flow can control the NL decomposition rate, which determines the surface roughness at the end of the annealing process [48, 49]. In Figure 2-3, after point (h) at which LT NL annealing begins, slight increase of reflectance is normally observed. The increase continues until around 800 °C at which GaN decomposition process starts to occur. Once the reflection intensity peaks, it begins to drop due to the increase in surface roughness. Initially randomly distributed islands start to be transformed into relatively uniform islands due to the decomposition of the NL and the migration of the gallium ad-atoms.During the annealing process, the reflectivity first decreases due to the increase of surface roughness. Further annealing results in a slight increase of reflectivity because at a higher temperature, the surface morphology becomes smoother. However, if we anneal the surface even further, the surface roughness increases again, which results in the decrease of reflection intensity [48, 49]. This phenomenon can be explained by considering the volume of the GaN islands. At the transition point ((k) in Figure 2-3), the volume of the islands per unit area becomes the highest which is preferable for the subsequent HT GaN growth. As a rule of thumb, the position of this (reflectometry trace) shoulder is dominated by the highest temperature of the annealing process [50]. In summary, the goal of the low temperature nucleation and the subsequent annealing is to achieve a surface morphology with proper density and sizes of the islands for the following HT GaN growth.As shown in Figure 2-5, even a slight change of the island distribution caused by a slight difference of the NL thickness and temperature ramping rate (Table 2-4) can result in a significant difference in the following HT GaN growth under the same conditions. In general, it takes longer for an NL with a rougher surface and smaller islands to be transformed into the 2D growth mode. The conditions to achieve high crystal quality GaN on sapphire are mostly related to the growth and annealing of the LT NL.2.1.1.5 HT GaN GrowthAs soon as the sapphire surface is covered with suitable volume, uniformity, thickness, and density of GaN islands, HT GaN growth can be followed. This HT GaN itself can be divided into two parts (Figure 2-6). Part I corresponds to the initial stage of HT GaN growth when the growth mode is transitioned from 3D to 2D, which affects the crystal quality significantly. In part II, GaN epilayer becomes thicker because the growth mode as well as growth condition is stabilized for 2Dmode. Several strategies to control the GaN growth in each regime will be briefly discussed in the following.The growth in part I is a buffer step to prepare a surface suitable for HT GaN growth. During this step, the oscillation of the reflectometry signal becomes increasingly obvious. Initially, the reflectivity continues to drop due to the increase of surface roughness induced by the coagulations of the islands, i.e. 3D growth. As time goes by, the 3D growth mode is suppressed and the 2D growth mode is enhanced. Once the surface becomes flattened due to the enhanced 2D growth, layer by layer growth of GaN begins, which causes the reflectivity to increase. The duration of this part of growth can be optimized by tweaking the reactor pressure, V/III ratio, and growth rate [51, 52]. For example, in the case of a low V/III ratio, it takes longer to recover the reflection intensity, which implies that the change of the growth mode (3D 2D) occurs more slowly. The reflectivity recovery time is critical to oscillation amplitude in part II. In general, a larger oscillation amplitude corresponds to a better crystal quality.The part II of the HT GaN growth is stable in a wide range of growth conditions because the growth occurs in a mass transfer limited region. Nevertheless, several key factors will still affect the crystalline structure, including the growth temperature, trimethyl-gallium (TMG) flow, NH3 flow, V/III ratio, and reactor pressure. As shown in Figure 2-7, the growth rate increases as the group III flow increases but decreases as the V/III ratio and growth temperature increase. The。
中国LED发展前景中英文对照外文翻译文献
中英文对照外文翻译The development prospects of the mainland State LEDLED doomed its huge market will develop into a huge industry. Overall, the domestic industry in terms of size has been unsatisfactory, the typical case is the integrated circuit industry and the LCD panel industry, the domestic IC industry is now tail between its people, LCD panel industry is riddled with illness, technology complex, large investment and a weak infrastructure is the main reason, while the LED industry will break the curse, and can bring about the upgrading of industries, such as the domestic industry in LCD driver chips simply do not drive, because the LCD panel industry out of the country, support because of huge market, LED Driver IC is expected to flourish in the country to promote domestic enterprises bigger and stronger, which in turn will promote the domestic LCD driver chip or other chip-driven development.China's LED industry is currently a disadvantage lies in the fact that a LED products of domestic enterprises and overseas technical level there is a certain gap in the pursuit of high-end customers at a disadvantage; Second, the domestic IC manufacturing base compared to Japan, Korea and Taiwan, these strong LED weak areas, LED epitaxy, chip manufacturing capacity, technological level and poor external support of some materials, the learning curve longer will take some time to cultivate; Third, the size of the domestic LED business is still relatively small, most of them did not exceed 100kk / monthly energy (bluegreen), this state of affairs in the next two years will be improved; four, domestic R & D concentrated in universities and research institutes, production in the enterprises, the lack of R & D results of the rapid industrialization of the conversion mechanism, which should be learn from Taiwan's Industrial Technology Research Institute of the technical achievements the licensing mechanism to speed up the conversion rate of technological achievements and scientific research institutes can not be for their own industry rather than the outcome of the latest technology and timely transfer to industry, the Government should regulate the development of relevant policy-related behavior; five domestic lack of core patents, in particular related to the industry in the long-term development of the Blu-ray core patents and patent lack of white light, which will enable long-term development of domestic industries to function. China's local enterprises at this stage is mainly at the initial stage, smaller companies, the manufacturers of the master do not constitute a threat to the patent, patent issues is not very prominent. However, with the development and expansion of domestic enterprises, once the scale to a certain extent, the "going out" development strategy, will become a potential patent issues. At present, the domestic enterprises to grow bigger, to improve product quality and technical level of the most important task is to improve the future licensing companies asking price at the time, or to gradually break through the core of R & D patents.We believe that the LED industry in China has good prospects for development, based on the following points: First, in terms of the technology, LED technology has the bottleneck of high growth, low-threshold characteristics of the study, the domestic long-term accumulation in the semiconductor field ofresearch resources can be useful with a good basis for further study. Although the manufacturing of integrated circuits based on weak, relatively low technological level, some domestic enterprises to join overseas technical personnel, continue to make breakthroughs in technology, technological level of domestic enterprises with good companies with the technological level of Taiwan or less the same as with international companies as a whole has been narrowing the gap; Second, LED invested relatively small initial investment will be 100 million plant, the domestic enterprises to enter the threshold of the low, easy to achieve a rolling development and manufacture of integrated circuits and liquid crystal panel manufacturers easily to tens of billions of billions of yuan in investment it is "insignificant" easier access to the domestic enterprises to form industrial clusters, of course, may also lead to vicious competition and to a certain stage of development of market integration; Third, the domestic market great, LED market is the next major general lighting market, the market capacity, end-consumer market, scattered and difficult to form a monopoly, a vast living space of domestic enterprises; Fourth, some companies have a core of intellectual property rights, such as crystalline silicon photovoltaic substrate can GaN-ray projects, Dalian Road, the area of the United States and the core of the chip technology, has global competitiveness of these enterprises on technology development in the demonstration effect easy to form and promote the healthy growth of the domestic business market; five, after maturity of the technology, LED downstream packaging and devices are labor-intensive production, the development of the mainland with the labor cost advantage.The development process from the LED industry, the global sales of LED according to the market is currently the largest mobile phone backlight market,with mobile phone sales growth slowing down, as well as the OLED screen on the mobile phone TFT-LCD screen to enhance the penetration of the global growth rate of the LED . Technological progress as a result of cost reduction in the current (and even pre-2010) is not enough to allow full access to general use LED lighting market, global growth will be the next notebook, LCD TV backlighting, and automotive markets with the car interior lamp backlight market. As the world's top five LCD panel (LG Philips, Samsung, AUO, CMO and Sharp) in a high level of LED technology, large production capacity in Japan, Taiwan and South Korea, domestic only BOE, polish electricity and the Five Dragon PV panels of three lines, the 4.5-generation Shanghai Tianma production line will be able to after the demand for LED backlighting, but the overall demand is not dominant, the domestic enterprises to enter the LCD panel backlight LED supply chain proceeds should not be too large backlit panel with mobile phone market is quite similar.Application of the Chinese market at this stage mainly in the architectural lighting, indoor and outdoor display, based on the above reasons, the main force of the next wave may be present in these markets, but in mobile phones, small size LCD backlight, automobile penetration will increase, and some scattered markets such as special lighting will open up even more (the cost of special lighting requirements for general lighting is not so harsh). After the replacement of a few years ago, LED traffic lights is very popular, as the LED's life is longer, the short term it is very difficult to replace in the event of large-scale work, which makes the LED traffic lights for a period of low demand period ; a large domestic sedan market, but higher, certification cycle length, as long as there is excellent product quality, domestic motor vehicle lights LED backlighting and avery large market demand and growth in demand in this market is relatively stable; and LED display its easy to assemble, low power consumption, high brightness, etc. has been widely applied to the banking, securities, squares, railway stations, sports venues, the future of this market there is still great potential for growth; in the Olympic Games, World Expo, a number of city night demonstration effect of the project, led by National Semiconductor Lighting Project, as well as the many favorable factors, such as the promotion of, the architectural lighting market is still a broad prospect.Generally speaking, a number of large international companies focused on high-end, more concentrated target market's "ready" market, as well as general lighting of the huge potential market, and some of the products will be relatively low technical requirements that the future control of the decentralized nature of the market so weak out of hand because of its large number of patents, do not worry about the future was out of the market at this stage not to pursue production capacity (per month to Nichia 500kk, Toyoda Gosei and Cree were 350kk and 300kk), and focus on technology to lead the market trend, When the technology is mature enough to be the size of the market into the general lighting, it is estimated that its production capacity will be rapidly and at the same time to reduce external licensing. This "center - periphery" of the competition is expected to maintain a long period of time.At present, the major manufacturers in the Mainland market, if the fear of chip exports will encounter two challenges: First, large international companies in patent litigation (mainly blue and white), in fact, as long as a certain size, regardless of the export and whether the patent will encounter challenges, but the export of patent litigation is more likely that a number of; Second, thecompetitiveness of other external vendors, especially manufacturers in Taiwan, Taiwan's traditional manufacturers followed their strategy - and technology to track the international companies, at the same time strongly improve productivity, reduce costs and production capacity in Taiwan the world's first chip, there are a number of other industries such as the giant Hon Hai, the Mau, the total being good to enter this area, can influence the future of Taiwan LED chip global market price fluctuations . Given the huge domestic market demand, domestic chip plants, even if it can rely on the domestic market of the development of an adequate, if the photovoltaic companies overseas unlimited access to domestic markets, domestic companies will face continued competitive pressures, which in the long-term domestic enterprises is a very negative statement. LED industry is growing at this stage, but also the layout of the LED makers a view of domestic, foreign investment in the Mainland to enjoy tax incentives, domestic enterprises to compete in an unequal position to enter the domestic market to foreign investors should be encouraged to set up factories in China to engage in outreach, chip core technology, such as enterprises, these enterprises can promote personnel training and raising the overall skill level; should be limited to those packages in the country, epitaxial, chip, such as part of the core technology for the occupation in the foreign market from the enterprise, Once such a business card in all core areas, and local enterprises do not enjoy the benefits of technological progress, development and limited space, I am afraid they will scramble to rely on price war, not so hard to curry favor with their own thing, so deal with only part of the current package in China to limit foreign investment, such as import tariffs levied on the chip.From the patent litigation is concerned, its not terrible, as long as our main competitors, have to pay, we still compete in the same starting line, Taiwan's major involving the blue and white LED chip factory in the growth process have experienced litigation LED , reached a settlement in the proceedings to obtain patents, continue to grow. The best response is to do at this stage a large-scale, access to patents, while at the same time strengthen its own R & D to improve the patent litigation in the bargaining power for cross-licensing. Domestic enterprises in terms of size, Xiamen San'an may usher in the growth of the first "baptism."The future industrial competitiveness will depend on two aspects, firstly, technology, including to improve light-emitting efficiency and lower the cost of technology to improve power device technology, the direction of the road there is an extension of existing technology, but also possible routes of new technologies; also including access to high-quality technology products, as well as external systems such as lighting design and technology-driven chip design; Second, the scale, on the one hand, due to large scale to reduce costs, the market strong bargaining power; On the other hand, compounds with IC wafer manufacture of silicon used is very different, even if an extension on the same production out of the chip performance may be quite different, which require relatively high consistency of application areas (such as a typical LCD backlight), the extension of an There is only a part of to meet the requirements, but large-scale enterprises, the number of levels of market structure, can be inconsistent with the requirements of a particular market deployment of chip products to another market, the company's total output to increase the efficiency of the full.LED industry a bright future, but only in the above-mentioned two aspects of the industry's leading enterprise is the future king. Conclusion: Company commented, domestic enterprises should be concerned about what?In the entire LED industry chain and which business concern? From the overall development process, the five companies most investment value.A class of intellectual property rights is a core business. Room for the development of such enterprises in the most broad-based domestic to Nanchang University established a joint private equity fund is the crystal can be a typical representative of photoelectric, photoelectric crystal can be made ofsilicon-based GaN epitaxial Blu-ray technology to the world's top three blue Light one process technology to break through foreign patents Nichia and Cree blockade, the company is set up near the current level of the industry need to be inspected; another Luming for Dalian, the company through the acquisition of American LED chip manufacturers to make chips AXT technology increases, access to more than 40 patented core technologies, as well as the technical team. In addition, Dalian Luming engaged in rare earth since the originallight-emitting material, white in the synthesis of fluorescent powder used in the production of an edge, is one of the world production of only a few can produce light-emitting light-emitting materials can chip business. Moreover, the possibility of R & D Luming new rare-earth fluorescent powder, breakthrough Nichia, Osram white light technology, such as patents, for the domestic industry into the general LED lighting breakthrough in the last barriers! White LED lighting as long as the two major "stumbling block" - Blu-ray patent and white patent to make a breakthrough, the domestic LED industry a bright future ahead for the rest of the domestic industry is to test the ability of the industry.Other enterprises in the chip industry and technology to track more successful doing business. Ability to carry out the actual chip design and processing of green extension of a certain size and mainly concentrated in the Saman Xiamen, Dalian Road, United States (Luming subsidiaries), several companies such as ShiLanWei, the current scale of production with LED-ray only Saman Xiamen. Xiamen, Taiwan MOCVD12 Saman, red chips per month can 1000kk, blue chip 200kk / month, technology in the domestic leading level, with full-colorultra-high brightness LED chip production capacity, sales revenue in 2006 nearly 300 million, the market was well received; Moreover, Taiwan's optoelectronics and informed Epistar to set up factories in Xiamen, the local formation of industrial clusters to enhance the capacity of industry and technical personnel supporting the flow of the importance of the development of the three also have an important role in promoting. ShiLanWei capacity of the current blue-chip 100kk / months, the level of advanced chip technology, the company will be in August two new MOCVD, into two next year, capacity will beblue-chip 300kk / months, when available bright red and green and blue LED chips, LED chip sales in 2007 expected to reach 200 million, with a certain scale in the market have a certain brand; ShiLan Wei Another advantage lies in its traditional integrated circuit design companies in LED Driver IC design and manufacture can make a difference, the company's products have been launched in this regard, it ShiLanWei also optimistic about the prospects for the development. Dalian Road in the industrialization of the United States also made a well-known, both intellectual property and the success of the industrialization of the characteristics of two types of development.The former two categories of enterprises are the core advantage of more concentrated, the investment value will first appear.The third type of enterprise is the best package of downstream businesses, such as Xiamen Hualian, Foshan State Stars electricity. The development of domestic-scale integrated circuits is a major feature of the area of local enterprise development package is better in the field of design and manufacture, it is estimated that in the field of LED packaging companies will also be a good development opportunities, or even faster than the upper and middle reaches of epitaxial chip business development, because the package can be purchased foreign chip companies to meet domestic market demand, while domestic enterprises will follow the road map chip technology progress. The field of LED, white LED light effect through the package to achieve some other color light source must also be packaged into a device for the terminal market, the level of packaging technology will directly determine the overall development of LED market! At present, mainly concentrated in the lower reaches of LED packaging industry, but the majority of low levels of enterprise package, leading to fierce competition, with the escalation of end markets, excellent downstream packaging increasingly strong brand, technology becoming more advanced, it is bound to come to the fore, the investment value of a to embody.The fourth type of enterprises will rise in the future of LED lighting in common areas, such as lighting design, professional brand developed a white LED general illumination light and lamp manufacturers, and so, as the largest market for LED applications, high-investment value of some enterprises a matter of course, only a matter of time rather long.The fifth type of LED industry chain in outlying areas of electronic materials, such as silicon, silicon resin, lead frame packaging, cooling module, etc. as well as the field of LED driver IC, current in these areas is still relatively weak, it is necessary to experience a long-term , driver chips are expected to grow faster than other outlying areas. LCD Driver IC domestic industrialization quite successful, to benefit small, mainly due to the lower reaches of the market (panel manufacturers) the lack of design and manufacture of integrated circuits based on relatively weak, and now a very broad semiconductor lighting to domestic downstream market-driven industrial development chip the opportunity to grow, it is believed that come to the fore a number of enterprises.As the further development of display device and technology, screen display system has been widely used in national economy, LED display as a carrier for displaying information is one of major media. LED display is composed by using LED lattice module or pixel unit.As computer technology developed, LED digital has the characteristics of high reliability, long life, high cost performance, low using cost, strongly adaptive capacity to environment which can be directly driven without reducing drive, therefore, it has been playing a importance role in the field of flat display. and for a long period of time, there are considerable room for development. So, it widely used in the financial markets, hospitals, stadiums, airports, terminals, stations, highways and other public places for information display and advertising.In recent years, China's LED display related technology has also been made a fast and great development, Because of early stage LED material and component restriction, LED display applications were not widely expand. Theother hand, display control technology basically is a communication control method which objectively affects the display effect. Thus resulting in the early LED displays in the country rarely, product based on double primary color which is green and red, communication control, gray level is single point of four tone gray, high cost. Later, the rapid development of LED display in the nineties, the global information industry is growing rapidly, information technology continue to make breakthroughs in various fields, LED display in the LED materials and control technology has also been the emergence of new results. The successful development of blue LED lens, full-color LED display to enter the market; the field of computer and microelectronics technology development in the field of display control technology, the video control technology, the screen dynamic display effect of greatly increased. In this stage, LED display in China has developed rapidly, LED display industry turn into a new high-tech industry. Today, LED display used in broader field, here I will talk my point about the LED in the hotel and leisure field applications.I LED display of the effectiveness of the hotelLED electronic display is the fourth largest advertising media after television，newspaper, network. It will bring tangible social benefits for investors and economic benefits, LED electronic display can be received from the computer, TV, VCR, VCD, video cameras and other information transmitted, and play dimensional or three-dimensional animation, text information at anytime.With economic grows, Accelerated pace of social work life, the hotel in people's lives plays a indispensable role. Hotel is a large population flow in today where it is a social gathering place for celebrities, of course, it is thewindow which needs information fastest, most accurate and huge. LED electronic display will be full of your customer's demand for investors with a huge, immeasurable, long-term social and economic benefits.1. SocialA. promote the hotel's services and preferential policies to enhance the hotel's image.B. promote the hotel's "service commitment" and other content, enhancing its visibility.C.beautify the hotel environment, to improve their grades and the taste is more conducive to attracting more customers a friend.D. Providing convenience to our customers.2. EconomicThe twenty-first century, a highly information-oriented era, corporate awareness of the advertisements has never been so strong and is growing; Hotels flow-intensive, information requirements wide; LED electronic display, a high information content of the display medium, a the world's best advertising media, can be, within 365 days a year to undertake a variety of advertising an unlimited number of foreign business; In good operation, will obviously about to create rising prosperity has brought enormous economic benefits. Guangzhou, China Trade Fair Exhibition Hall next to a large full-color screen, at an annual tens of millions of dollars in advertising revenue for investors rolling in wealth; Xiamen Egret Plaza on the state of large-scale full-color, in just three years time, the recovery of more than 500 million yuan of total investment, and is nearly 200 million a year net profit for the investors steady flow of economic benefits.The foregoing analysis, the Grand Hotel to configure a large LEDelectronic display, will give you and your guests with huge, long-term, good social and economic benefits, play a double-edged sword effect.ⅡThe role of hotel LED display1.Heat the hotel mood.Through the display screen to play the higher-ups and all kinds of guests come to visit, guide words of welcome, a variety of major festivals such as celebration of the word.2.Knowledge spreadingA.through the LED electronic display that can play a variety of laws, rules, regulations and all kinds of knowledge and so on.B.through the LED electronic display can play hotel new service introduction; the hotel's "service commitment" and so on.3. Play the role of bulletin boardsThrough the display screen can be broadcast lectures, meetings of the notice, all notices, job placement and advanced individuals, the Hall of Fame and advanced deeds and so on.4.played the role of public service ads①through the display screen can be broadcast weather forecasts;②local culture, history, geography, climate profiles, local customs and habits;③ local maps, tourist traffic map and various tourist spots, maps;④"civilized citizens of the Convention", the hotel's slogan and important news.5. Creation of well economic benefitsAs the world's best advertising media, also carry advertisements of major companies, (the proposed dual-color or full color, so that the content displayed on the rich and colorful, more attraction to major companies and units undertake activities and doing advertising, enhance the hotel to be well known, fully reflect the grade of the hotel).Overall LED display in the hotel for the advancement of hotel services to the public image, reputation, service grade, and create a civilized window.ⅢThe characteristics of LED display1. Display is of bright and longer visual distance, which reaches to 500m can be seen clearly.2. Display shows the simple and colorful contents that will not bring banners or other display device and the thick rough sense of feeling.3. Display is green lighting with the characteristics of long life, low power consumption, without extra IR / UV spectra of mercury-containing hazardous substances.4. Display is a high-tech product, it will be used to quickly align your company with the times.5. The development prospect of display is extremely broad, in government agencies and enterprises play an important role in office. The adoption of the display system will enable your company's information technology step to high level.China's economy is developing rapidly, there is increasing number of dissemination of information requirements. It is believed that, led electronic display with its bright colors, display informative, long life, power consumptionis small, light weight, space for small size, high stability, easy operation, easy installation and maintenance, and other characteristics played a role in thesocio-economic development becomes more important. Somehow seems, led screen display in today's media, the best cost performance, is your best choice.中国本土LED的发展前景LED自产生以来就具有广阔的发展前景。
LED相关翻译_英文
Using LED Lighting for Ubiquitous Indoor Wireless Networking Abstract—Wireless networking is currently dominated by radio frequency (RF) techniques. However, the soon-to-be ubiquity of LED-based lighting motivated by significant energy savings provides an opportunistic deployment of widespread free-space optical (FSO) communications. LED-based network transceivers have a variety of competitive advantages over RF including high bandwidth density, security, energy consumption, and aesthetics. They also use a highly reusable unregulated part of the spectrum (visible light). In this paper we describe results from a pilot project to demonstrate the viability of an optical free-space visible light transceiver as a basis for indoor wireless networking. Inexpensive, commercial, off-the shelf LEDs and photodiodes were used to construct two prototypes; a simplex channel as expected as a component of an asymmetric/hybrid RF-FSO system, and a full-duplex channel demonstrating the ability to isolate multiple channels. On-off keying (OOK) was applied without observable flicker in the target modulation ranges. Results indicate the viability of creating inexpensive FSO transceivers that might be embedded in commercial lighting products to support ceiling-to-floor distances of approximately 3m.Index Terms—Wireless networking, indoor communications, free-space optical communications, visible light LED, modulation, OOK: ON OFF Shift Keying, FSO: Free Space Optics, RF: Radio Frequency.Ⅰ.INTRODUCTIONWIRELESS networking is dominated by the use of radio frequency (RF) techniques. The desire for low-cost, high-speed links has motivated recent interest in infrared wireless communication. At the same time the rapid development of new LED ma terials in the visible spectrum, particularly “white” LEDs motivates consideration of visible light as a communication medium since it is expected to be widely adopted as the next form of illumination. With its significant energy savings over incandescent and compact fluorescent technologies this adoption creates an opportunity in the replacement of devices. Because LEDs are easily modulated for communications, there is a corresponding opportunity to insert wireless LED-based communication into these illumination devices as introduced by the Visible Light Communication Consortium in order to provide indoor communication link through a power line (PLC).The LED-based visible-light optical channel becomes a very attractive complement or even substitute for RF techniques. A good example is the RONJA project in Czech Republic for outdoor application were the data link can network neighboring houses with cross-street Ethernet access, solving the last mile problem for ISP‟s, or provide a link layer for fast neighborhood mesh networks. It has advantages of large potential bandwidth (THz) with no regulation or license fee. Optical communication with lasers is successfully employed today; however, simple LEDs, as shown in this paper, can be used for the required distances and in the context of noise sources indoors, where we expect to apply LED-based lighting. Finally, in addition to lower energy consumption LEDs have a significantly longer lifetime and are safer for the environment as they lack the harmful ingredient of mercury.To demonstrate the concept and prove viability, we have sought to create two prototypes to capture scenarios associated with future access points providing LED-based indoor networking. The first is a simplex channel characteristic of one-half of an asymmetric hybrid RF-FSO model in which data may be downloaded at high speed from overhead illumination to a receiver.In such a hybrid model we can isolate asymmetric traffic and benefit from the line-of-sight characteristics of light and its channel isolation. The second model is of a full-duplex channel on which we can support the construction of a network interface for multiple access embedded in ceiling lighting. A photo of the simplex channel is shown in Fig. 1. Using off the shelf components, the prototype supports communication between two computers using a serial link. The transmitter and receiver are powered by 9V batteries.The simplex channel permits transmission in one direction only. Fig. 2 shows the overall signal flow. By connecting computers at each end we can demonstrate the transmission of ASCII characters from one terminal to the next using the visible light channel. The signal chain uses visible light through an array of 10 LEDs. The receiver employs an array of 3 photodiodes and corresponding OOK decoding circuitry. In the remainder of the paper we describe related work in LED-based communications, modulation, frequency considerations, performance, and the duplex channel. Section VII concludes the paper.II. PRELIMINARIESA. LED vs. LaserLEDs are constructed from direct band-gap semiconductor materials whose band-gap energies correspond to frequencies in the visible spectrum. In order to make LEDs efficiently emit light, this is typically accomplished through forward biasing a p-n junction. The current flowing through the junction allows for the rate of the radiative electron-hole recombination to be large. The light emitted from this radiative recombination is in the form of spontaneous emission and is radiated uniformly in all directions. Laser diodes are made from similar materials as LEDs however they are generally more heavily doped to allow the materials to act as a semiconductor optical amplifier. As with all lasers feedback is required. In laser diodes it can take the simple form of cleaved surfaces which take advantage of internal reflections from the difference of indexes of refraction or engineered Distributed Bragg Reflectors. Typical characteristics of LEDs and Laser diodes that can be used as a basis for comparison are their respective spectral intensities, efficiencies, and output optical powers. The spectral intensity of LEDs is very broad in comparison with that of the laser diode which is very narrow as a result of stimulated emission. Overall laser diodes are also more efficient with respect to power conversion efficiency and the output optical power is generally much greater. Laser diodes can be characterized by high intensity, spatially confined beams of light.LEDs on the other hand produce light that is not spatially confined and diffuses readily. From a communications standpoint, using laser light as the medium allows for significantly greater distance separations and higher data rates and such application is already being developed with promising results of 1.9km at 10Mbit/s full duplex Ethernet. LEDs can provide illumination but because they produce diffuse light they are more sensitive to separation distances.B. Optical ComponentsIn considering relevant LEDs to select for a prototype for supporting illumination and communication, we first evaluated LEDs from a consumer flashlight. Two of these flashlights used were disassembled, and the LED arrays were removed. The flashlights belong to the ProPolymer series manufactured by Streamlight. The choice of photodiode to begin experimentation was based primarily on price and availability, as well as the fact that it must be sensitive to the visible region of the spectrum. Osram‟s SFH213 photodiode was chosen. A snapshot from this device‟s datasheet (Fig. 3) shows its spectral sensitivity and directional characteristics.Visible light ranges between wavelengths of 400nm (violet) and 700nm (red). Notice that the spectral sensitivity of this photodiode actually peaks beyond the visible region, in the near infrared, where the majority of FSO research resides. Photodiodes with peak sensitivity in the visible region are not in high demand, and hence are difficult to find in the commercial market. This component was chosen with the expectation that 90% relative sensitivity at 700nm was sufficient. The received signal ultimately is to be translated into a bit stream, so attention was also given to the rise time of the PIN photodiode. The SFH213 on Fig. 3 is advertised to have a 5ns rise time. The term …PIN‟ refers to the composition of the photodiode (p-type, intrinsic, n-type) and is used interchangeably with the term …photodiode‟ in this paper. We assumed that purchasing a photodiode with a preamp would substantially increasethe range of the received signal. Hamamatsu‟s S6468 Silicon PIN was chosen based again on the spectral response and fast rise time.The separation distance (distance between LED and Photodiodes) was measured by powering the LED array with a function generator (2V peak-peak square wave with a 1V offset). Following these experiments (Fig. 4), we decided to use the SFH213 components for the prototype and incorporate an external amplifier in the design.We expected that the overhead lighting in the laboratory would interfere with the signals transmitted by the LEDs and preparations had been made to purchase optical filters and focusing components to alleviate this problem. During experimentation, a second advantage to using the SFH213 was discovered in the inherent directionality of the PIN. The operator needed to carefully align the photodiode with the LED array to obtain realistic signal readings, but with the photodiode pointed along the table (perpendicular to the overhead lights), there was minimal background noise. The directional characteristics of the PIN (shown in Fig. 3b) allow experiments to be conducted, and the prototype to be demonstrated, in a normally illuminated room. Furthermore, the size and shape of the SFH213 permitted reuse of the flashlight reflectors to contain the accepted light. The reflector on the flashlight functions to increase the forward intensity of the LEDs by redirecting the backward scattered light. Having a reflector at both the transmitting end of the prototype (around the LEDs) and the receiving end (around the photodiodes) inevitably increased the performance of the system.III. FREQUENCY CONSIDERA TIONSWe decided to use On-Off Keying (OOK) as a modulation scheme meaning that the frequency study is very important in the photonics components and in the circuit design of the communication interface.A. Photodiode ResponseThe frequency characteristics of the photodiodes purchased proved to be a limiting factor of the maximum achievable data rate of our system. The Osram SFH213 photodiodes advertised rise and fall times of 5 ns, which would directly translate to an upper bound frequency of 200 MHz. Initially we set up the photodiodes reverse biased, connecting in series to a 100 kΩ r esistor going to ground. We found that when we applied a square wave with a frequency of 10 kHz that it became distorted and appeared as a saw-tooth function instead of the square wave. Initial suspicions were directed at the LEDs as the limiting component on bandwidth. However, when we set up the Hamamatsu photodiodes we found that in fact the limitation was caused by the photodiodes. By readjusting the resistive component in both the sender and receiver we were able to increase the input frequency to the 50 kHz range.B. V oltage Reference Effect on FrequencyAnother factor that affected the maximum frequency of the system was the value of the voltage reference for the comparator to convert to TTL logic. Using the slope coupling trigger feature of the oscilloscope we were able to see the actual signal for a given ASCII character. Due to the saw-tooth behavior of our photodiodes at high frequencies, the photodiodes were not able to make full transitions in the short bit times required. Therefore, raisi ng the voltage reference we were able to “catch” these incomplete transitions. However, the reference voltage also needs to be a low enough so as not to mistake noise as the signal and make false transitions. We found that by using a reference voltage of three volts we were able to achieve data rates above 56 kbps.IV. COMMUNICA TION INTERFACEThe communication interface subsystem is the design of the hardware interface that will modulate and demodulate the signal using OOK modulation scheme. Several infrared research prototypes described in [3] and [4] used OOK with a successful implementation in the range of 5-20Mb/s. The block diagram circuit of the simplex channel that we designed is shown in Fig. 5.A. Transmitter CircuitA link between the USB/RS-232 cable and the LEDs was necessary to convert the signal from serial to TTL. Our original design is based on a laser transceiver circuit. It consists of an opto-isolator (4N33) and a hex-inverter (open collector) also used in as a key design. The opto-isolator couples a standard RS-232 signal from the computer to the driver section of the circuit. The hex-inverter has all its output coupled together to provide enough drive current for the LEDs. This configuration was designed so that when no signal is present the LEDs are still ON. Once the transmitter circuit wassuccessfully working, we switched the opto-isolator with the MAX232A chip (transceiver).B. Receiver CircuitThe noisy low power signal received from the photodiodes was sent to the input of an LM741 operational amplifier. The amplifier had a non-inverting gain of 51. This amplified version of the signal was then sent to the AP393 comparator so as to clip the amplified signal between 0-5V making it TTL. As mentioned previously we used a reference voltage to set the transition point which was a critical value in determining the maximum frequency attainable. The output TTL voltage from the comparator was then sent to MAX232A transceiver chip so that it can be sent over the USB/RS232 cable to the laptop.V. ANALYSIS, SIMULA TIONS, & RESULTSTo characterize the performance of the design we studied the distance versus intensity and also the link budget of a simplex channel. A link budget is the accounting of all the gains and losses from the transmitter, through the medium (free space, cable, waveguide, fiber, etc) to the receiver in the communication channel. It accounts for the attenuation of the transmitted signal due to propagation, as well as the antenna gains, feedline and miscellaneous losses.A. Distance vs. Intensity PerformanceOnce the photodiode component had been selected, various configurations were tested to find a scenario that promised a range of 3-5 meters. During this phase, the PINs were not mounted in a reflector and two LED arrays (from the flashlights) wereavailable. The measurements shown in the chart below were conducted with a separation between light source and PINs of three feet.Although the two LED arrays appear to give better results than a single LED-array, this option would eliminate the possibility of packaging the final prototype within the footprint of two flashlights (one at each end). Also, a third reflector would then need to be integrated. Finally, to fully gain the advantage of two LED arrays the photodiodes should be separated and centered on each individual array rather than focused at the center of the combined arrays [9].Fig. 7 shows that the slope of the drop-off with distance for two LED arrays and two PINs remains the same as with one of each component, but the initial values are much lower. Compare the first point in the graph below at approximately 300mV to the first point in Fig. 7 at approximately 1500mV. Upon completion of the simplex channel, data rate and distance parameters were simultaneously tested. A table of the results is shown below:This table clearly shows that the speed of the simplex channel is related to the distance of the transmitter and the receiver. For a faster baud rate and no errors we need to decrease the distance (i.e., 48,000 Baud for almost 3m). If we increase the distance we need to reduce the baud rate (i.e. 9600 Baud for almost 4m). This is a first step in accomplishing a link using visible light. In comparison a non-directed IR system achieves a 4.2-m range at 70Mb/s.Table I characterizes the simplex prototype and is a proof of concept of FSO technology using visible light. Using this type of USB/RS-232 cable, the maximum speed is inherently limited to 1MB/s. However, higher data rates are feasible with closed-loop signal recovery at the receiver, which was not employed in our simple circuits. In terms of power consumption, the receiver of our prototype consumes 25mA while the transmitter consumes approximately 250mA, mainly to power the array of 10 LEDs.B. Link BudgetLine of sight visible light propagation is generally a simpler topic than RF propagation as far as link budget is concerned. Although the same principles are used, terms like antenna gain, free space loss and multipath fading have different interpretations. A link budget based on IRDA protocols was designed. The theoretical results were very close to the experimental ones and also gave us an understanding of how changing the physical properties would improve the performance. The Link Budget is as follows:An input power per LED of PTX = 125mW, an LED half angle of α = 10º and of solid angle s = 2π(1-cos(a)), an equivalent radiation intensity of Ie = PTX/SIe, and an irradiance of photodiode of Ee = 1mW/cm².Since we are not using a pre-amplifier before the transmitter and the ambient light is the same as the data-carrying light, the noise power is negligible. The results are shown below:As can be seen from the figure the maximum distance D Max that can be achieved is not linearly related with the number of LEDs and photodiodes. This was in compliance with the experiments where the improvement in performance was not significant after increasing the number of LEDs to 10 and number of photodiodes to 3. Fig. 9 shows how much of an effect the half angle, and in turn also the solid angle of an LED, has for the maximum distance that can be attained.The SHF213 photodiode has a switching time of 5ns which implied and upper bound on data rate of 200Mbps. The experimental data showed, with open-loop receiver showed a limit of approximately 48Kbps. Ultimately the performance limit is dictated by the RC time constants/slew rates of the more limiting of the LED or the receiving photodiode. For the particular LED employed in our prototype, a 50% duty cycle with OOK has a limit of 100 KHz under the resistive components of the driver. Clearly there is an opportunity for improving performance with more elaborate modulation, drivers, and clocking circuits.VI. DUPLEX CHANNELA duplex communication system in our context is formed by two simplex channels. The support of bidirectional communication is essential for the support of network interfaces that permit multiple access and indoor networking. Conceptually theduplex prototype involved laying components corresponding to the simplex channel in parallel but opposing directions. However, the selected (duplex) transceivers permitted reuse of some components at each end. A schematic of the duplex prototype is shown in Fig. 10. One of the challenges was to design a transceiver that would utilize the flashlight reflectors by combining both LEDs and photodiodes without crosstalk.A. Simplex vs. Duplex: LEDs & PhotodipdesTo transition from a simplex channel to a duplex channel, it was necessary to reconfigure the components within each reflector. Rather than having one reflector completely populated with LEDs and another with just three central photodiodes, both reflectors needed to contain some number of both LEDs and photodiodes.Recall that the directionality of the photodiodes requires that they be aligned with the most intense portion of the incoming beam. The circular arrangement of the LED‟s within the reflector leads to the center of the bea m having the highest intensity at some distance away from the source. These two physical considerations led to a duplex design where the two sides are identical, with 7 LED‟s around the perimeter of the reflector and 3 photodiodes in the center. The LED‟s could not easily be removed from the flashlight circuit, so independent LED‟s were chosen andpurchased.B. CrosstalkIn order to create a compact design we included both the transmit and the receive arrays on the same reflector that we used for the simplex channel. This led to the problem of crosstalk which affects our ability to receive data. In order, to reduce this problem we proceeded by wrapping the arrays of photodiodes with black electrical tape to reduce the effects of the local transmitter (Fig. 11 (b)).This setup was beneficial, however it did not completely isolate the photodiodes from crosstalk and the reflectors actually served to be detrimental. The oscilloscope plots are shown in Fig. 12.The first picture shows the effect of crosstalk with reflectors and the second image shows the received signal without the reflector. It can be seen on the crossta lk is more sever with the reflectors and this is because the reflected light by the local transmitter would also be recognized by the photodiodes at the small distances of separation that we were testing. Without the reflector the crosstalk is extremely diminished as shown in the figure on the left.C. ResultsThe full duplex circuits, based on their origin of the simplex design, were anticipated to have similar performance limitations. In practice, we observed lower data rates due to the limitations of the breadboard implementation. This configuration was inconclusive in terms of the noise introduced by the illumination component, the bidirectional crosstalk, and other potential effects. The prototype level would be to integrate the system into ceiling lighting using Power-line.VII. SUMMARYThis paper considers the opportunity provided by the replacement of existing illumination systems with LED-based lighting and the potential to introducefree-space optical networking with LED transceivers. We developed simplex and duplex transceiver prototypes as part our investigation and demonstrated their expected and achieved performance. In summary, using off-the-shelf LEDs and photodiodes we were able to demonstrate viable communication using visible light in the presence of normal room illumination. These results are promising for the potential to create more sophisticated network interfaces that both improve medium performance and provide multiple-access for ubiquitous indoor networking.。
LED点阵显示-外文文献及翻译
译文：大屏幕显示系统的研究LED的发展随着计算机技术的高速发展，LED屏幕显示系统作为继电视、广播、报纸、杂志之后的“第五大媒体”正快速步入社会生活的各个方面.它集微电子技术、计算机技术、信息处理技术于一体，可以将信息通过文字、图案、动画及视频四种形式显示出来。
与电视墙、磁翻板等媒体相比，LED大屏幕显示系统具有图案美观、色彩亮丽；图案、色彩变化丰富、快速；低功耗、长寿命、使用成本低、工作稳定可靠等特点。
它显示的图文视角大、视距远，因而已广泛应用于大型广场、商业广告、体育场馆、信息传播、新闻发布、证券交易；它还应用于工业控制和工业调动系统,便于把各种参数、报警点、工艺流程显示得更加清晰完美，可以满足不同环境的需要。
LED显示屏是一种利用计算机和复杂数字信号处理的电子广告宣传屏。
它的屏体部分由微处理器（主要是单片机）和驱动电路控制运行，显示的图像或文字由计算机编辑软件编辑获得。
由于LED显示屏这种新一代信息显示设备具有显示图案稳定、功耗低、寿命长等特点，而且它综合了各种信息显示设备的长处，并且克服了自身的不足，特别是由于一幅显示屏可以显示不同的内容，显示方式丰富.所以在公共场合,它具有强烈的广告宣传和信息传递效果，日趋在固体显示中占主导地位。
LED显示屏的发展前景极为广阔，目前正朝着更高亮度、更高耐气候性、更高的发光密度、更高的发光均匀性、可靠性、全色化方向发展。
由不同材料的半导体组成能发出不同色彩的LED晶点。
目前应用最广的是红色、绿色、黄色LED。
而蓝色和纯绿色LED的开发已经达到了实用阶段。
LED显示屏的分类LED显示屏是多种技术综合应用的产品，涉及光电子学、半导体器件、数字电子电路、大规模集成电路、单片机及微机等各个方面，既有硬件又有软件。
LED 显示屏是作为广播、电视、报纸、杂志之后的又一新传播媒体。
目前LED显示屏根据使用场所不同,可以分为室外屏和室内屏两种，其主要区别是发光管的发光亮度不同。
LED显示屏中英文对照外文翻译文献
LED显示屏中英文对照外文翻译文献(文档含英文原文和中文翻译)译文：大屏幕显示系统的研究LED的发展随着计算机技术的高速发展，LED屏幕显示系统作为继电视、广播、报纸、杂志之后的“第五大媒体”正快速步入社会生活的各个方面。
它集微电子技术、计算机技术、信息处理技术于一体，可以将信息通过文字、图案、动画及视频四种形式显示出来。
与电视墙、磁翻板等媒体相比，LED大屏幕显示系统具有图案美观、色彩亮丽；图案、色彩变化丰富、快速；低功耗、长寿命、使用成本低、工作稳定可靠等特点。
它显示的图文视角大、视距远，因而已广泛应用于大型广场、商业广告、体育场馆、信息传播、新闻发布、证券交易；它还应用于工业控制和工业调动系统，便于把各种参数、报警点、工艺流程显示得更加清晰完美，可以满足不同环境的需要。
LED显示屏是一种利用计算机和复杂数字信号处理的电子广告宣传屏。
它的屏体部分由微处理器（主要是单片机）和驱动电路控制运行，显示的图像或文字由计算机编辑软件编辑获得。
由于LED显示屏这种新一代信息显示设备具有显示图案稳定、功耗低、寿命长等特点，而且它综合了各种信息显示设备的长处，并且克服了自身的不足，特别是由于一幅显示屏可以显示不同的内容，显示方式丰富。
所以在公共场合，它具有强烈的广告宣传和信息传递效果，日趋在固体显示中占主导地位。
LED显示屏的发展前景极为广阔，目前正朝着更高亮度、更高耐气候性、更高的发光密度、更高的发光均匀性、可靠性、全色化方向发展。
由不同材料的半导体组成能发出不同色彩的LED晶点。
目前应用最广的是红色、绿色、黄色LED。
而蓝色和纯绿色LED的开发已经达到了实用阶段。
LED显示屏的分类LED显示屏是多种技术综合应用的产品，涉及光电子学、半导体器件、数字电子电路、大规模集成电路、单片机及微机等各个方面，既有硬件又有软件。
LED 显示屏是作为广播、电视、报纸、杂志之后的又一新传播媒体。
目前LED显示屏根据使用场所不同，可以分为室外屏和室内屏两种，其主要区别是发光管的发光亮度不同。
外文文献--翻译--led显示屏
外文资料原文Large screen display system’s researchLed developmentAlong with computer technology’s high speed development，LED （Light Emitting Diode) the screen display system takes after the television, the broadcast, the newspaper, the magazine “the fifth big media” marches into the social life fast each aspect。
Its collection microelectronic technology, the computer technology, the information processing and management technology in a body, may the information through the writing, the design，the animation and the video frequency four forms demonstrates. With media and so on bank of television monitors，magnetism vane compares，the LED large screen display system has the design to be artistic，the color is sharp; The design，the color change are rich，are fast; The low power loss，the long life, the use cost low, work stably reliable and so on characteristics。
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多个LED发光装置的新型采集系统
作为光源的一种，发光二极管（LED）有很多优点。
LED集成度更高，颜色种类多，使用寿命更长，而且工作电压较低。
但是，它仍有一个非常大的缺陷：一只LED的光照强度还是比较低。
这个缺点导致显示屏上的光通量不会很高。
但是无论如何，LED还是以其出色的性能在低电压装置中普遍应用。
因此，利用此系统采集多个LED的光，集成为更高强度的照明装置。
本设计提出三种采集系统，来实现增强光强的功能。
效率最好的一种采集系统可以达到96%。
同时，还分析了本系统的制造误差以及预算。
1 简介
利用传统的光源来设计一个便携式探照灯，尺寸和能耗会很大。
而利用LED 来设计将会避免这些问题。
LED有很多优点：节能、体积较小、使用寿命长（约100,103小时）等，尤其是LED的光很适合环境工作。
Carel Zeiss和Philips打算用LED光源设计两种便携式探照灯。
尽管LED有诸多优点，可以让他们设计出的探照灯更加便携和小巧，但是由于光学元件的转换效率问题，导致系统有很多困难。
解决这个困难将是本文研究的重点。
通常，用一种合成非线性集中器（CPC）来减小分散度。
但是，这种传统的CPC采集效率仅为72%，必须要改善采集效率来提高光的利用率。
本文中将解决分散度和采集效率两个问题。
为实现这个目标，设计了三种不同的采集系统，以提高效率，下面逐一介绍。
2 仿真部分
利用光学仿真软件和标签查找模块（BRO），来设计并分析采集系统的性能。
LED光源部分来自Osram-Opical半导体。
远程LED光源是一种Lambertian模式，LED的规格见表1。
在采集系统的底部有四个LED。
系统各个LED之间的位置关系如图1。
通光部分为2.1×2.1mm2，孔径3.26mm。
LED阵列对称的分布于系统的底部。
采集系统的第一个光学元件为均质器。
这个均质器的受光角度是12.5°。
因此，这个系统就是要把LED的受光角度的范围控制在±60°到±12.5°之间。
均质器的收集效率和能量分布能用来判断此采集系统。
3 新采集系统的说明
这里是三个新的采集系统：示踪的新设计I，新设计II，新设计III。
在下一
章节，将对采集系统的结构、采集效率和传统的合成非线性集中器（CPC ）和新的采集系统的能量分布进行阐述和分析。
3.1 传统的合成非线性集中器（CPC ）的设计
图2给出了传统的合成非线性集中器（CPC ）的结构。
用某种形状的侧反光板来收集从光源发射出来的光线。
合成非线性集中器（CPC ）的入口领域完全覆盖了LED 的光源。
见这平面横截面所有的边缘发出的光线发射器作为平行的光线离开合成非线性集中器（CPC ）。
CPC 的长度服从下面的关系式：
通常来说，一个传统的合成非线性集中器（CPC ），它的发散角和长度是成反比例的。
因此，如果一个传统的CPC 被用于采集系统，体积需要得到显著降低则散度角度会太大。
图3（a ）给出了从传统的合成非线性集中器到均质器的能量分布预测。
能量分布从均质器验收角度是±12.5°时产生分歧。
从图3（b ）中可以看出：收集的综合的能源效率流量和不同倾角只有72％在均质器的接受角度之内。
图1 LED 芯片之间的相对位置
图2 传统的合成非线性集中器（CPC ）的结构
3.2 包含透镜和反射镜的混合系统
图4给出了新设计I 的结构和射线追踪图。
对于这个准直透镜仪的设计，贝塞尔曲线被用于调制采集系统的形状。
新设计I 可以分为俩个部分：在中心的准直透镜、在侧面的反射器。
LED 在一个小于40°的角度发出的光线在镜头的中心会变成平行光。
图5给出了新设计I 中，穿过均质器的能量分布。
中心能量分布的下沉是由于在新采集系统的中心没有LED 光源的事实。
图中可以看出，
能量大都集图3 传统cpc 的能量分布和采集效率
图4 新式I 的结构和射线追踪图 图6 新式II 的结构和射线追踪图
图5 新式I 的结构和采集效率
中分布在±12.5°范围内。
这种现象在图5（b）中也可看出。
这是因为整合的穿过
均质器对抗倾斜角区域的能量能达到93％的采集率。
3.3 菲涅尔透镜和反射镜
图6给出了新设计II的结构和射线追踪图。
新设计II可以分为两部分：在中间的菲涅尔透镜和环绕在周边的反射镜。
由于LED相对狭窄的频谱波长，依赖于菲涅尔透镜装置的红外线波长可以被运用到此采集系统。
为了使装置的体积达到最小，用菲涅尔透镜的一种热射入取代了传统的镜头。
由于它的应用，获得了这种厚度只有10㎜的装置。
菲涅尔透镜的主要作用是收集射线以保证发光角度小于40°。
如果发散角在50°到90°之间，侧反光板便控制光线方向以确保光线到采集系统的中心。
然而，40°到50°之间仍有缺口。
新设计II的能量分布图在图7（a）中给出了。
可以认为，在新式II中的能量和新设计I中是相似的。
能量被集中于均质器的中心。
图7（b）中可以看到，新式II能量采集效率可以达到96％。
图7 新设计II的能量分布和采集效率图
3.4 抛物线型反射器
III 型的结构和光线追中如图8。
III 型在外表上和传统的CPC 很相似。
为了避免传统CPC 的过低的收集效率，在侧反光板用了一个贝齐尔曲线，且收集效率被用作最有条件。
主体只是一个反射器，所以它继承了传统CPC 的低成本。
光传播的方向是被这个侧反光板所控制的。
III 型的能量分布如图9。
与I 型和II 型相比，能量分歧角度比较大。
这一现象例证了它较低的收集效率。
通过均质器，收集效率如图9（b ），为76%。
图8 新设计II 的结构和射线追踪图
图9 新式III 型的能量分布和采集效率图
图10 新式I的照片图11 新式III型的照片4 容错性分析
显示移位和倾斜容错性的表格2中显示了3个采集系统的容错性。
采集率可用来判断容错性。
新设计II拥有3个设计中最好的采集率和最低的容错性。
但是，在移位和倾斜容错性测试中采集率下降到甚至低于50%。
新设计III在移位和倾斜容错性中只有中等性能。
容错性测试后的采集率有大约60%.移位和倾斜测试后新设计I表现出了最好的容错性。
采用通用标准的20%，采集率仍为约80%。