LED背光的设计与优化(LightTools)
LightTools-照明设计解析软件
O P T I C A L R E S E A R C H ASSOCIATES 高峰
目录
1.引言
本文目录 结构
2.LightTools的组成模块
3.LightTools的应用领域
1.引言
LightTools是美国Optical Research Associates开发的真正意义上的照 明设计解析软件。内置3维CAD建模功能，在LightTools中可与任意的模块 进行组合，可自由设定反射、透射、散射、偏振光、薄膜等的光学特性。 可高精度、快速获得这些特性的照度分布、亮度分布、色度分布等计算结 果。LightTools依靠操作方便和丰富的设计功能模块，获得最佳的测试结 果，是一款卓越的照明设计工具。
2.LightTools的组成模块
★接收器设定 1.接收器（面、远场接收器） 2.表面的照度 3.亮度分布解析 4.光学系统整体的配光分布解析 5.滤光功能（面、波长、光路长度等） ★各种解析结果 1.2种亮度输出（空间亮度计，角度亮度计） 2.测试角度、范围的设定 3.散射图（光线和感光面的交点显示） 4.光栅图（伪彩表示） 5.线图 6.面图（3D阴影显示） 7.LumViewer（光栅、面、线同时显示） 8.CIE色度图输出 9.照度、角度强度分布的RGB输出 T功能（各光路的评价·解析、杂散光解析 11.光路追踪功能——光路的评价解析、杂散光解析
2.LightTools的组成模块
Solid Works Link Module
1.在Link的状态下，可以直接在LightTools中输入在Solid Works中制作的元 件和装配件。 2.在SolidWorks Link Module中设定的尺寸等参数可以直接在LightTools中编 辑。 3.与在LightTools中制作的其他元件相同，通过最优化功能能够自动修改在 LightTools中可编辑的SolidWorks模型的参数。
LightTools功能与应用简介
– 可將 3D Texture 轉換成實體形狀 – 具有修復功能
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4
材料特性
• LightTools 提供各式的材料特性
– 玻璃（Schott, Hoya, Ohara, China…） – 塑膠（PMMA, PC, PS…） – 特別材質（AIR, Silicon…） – 自訂材料
功能與應用簡介
思渤科技 光學業務部 optical@
LightTools 介紹
• 1994 正式發行 • 以模組化方式提供使用 • 發行公司：Optical Research Associates（1963）
Epoxy Package
分析結果 OK
資料輸出
NS Ray Parametric control
最佳化
最佳化 NG
設計過程
7
3D 實體模型
• 以實體物件來表達
– 所有特性都可作控制（形狀、材料、表面） – 材質：折射率、吸收率、體散射、偏振 – 表面：穿透反射吸收、散射、塗膜、偏振、Fresnel loss
• 可進行
– 布林運算 – 移動、複製、尺寸和旋轉 – 膠合、沈浸
• 是非常好用的分析工具，尤其是雜散光的分析
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情境模擬 Photorealistic Rendering
• 照明模組的功能 • 允許使用者建構如照片般真實的影像
– 可模擬模型未發光與發光時的情景
環境光
情境光
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最佳化（優化）
• 最佳化就是根據標準或誤差函數，透過自動計算來改善系 統性能
• 最佳化三大基本組成：
– 誤差函數 Merit Function (Error Function)： • 系統的目標函數，是單一的數值。若該數值為 0 表示已經達成目標
LightTools优化教程
LightTools优化教程LightTools 优化教程⽬录第⼀章开始优化的基本概念什么是照明设计结构和要求软件的⽤途什么是优化？LT 优化照明系统优化有何特别LT 优化的特别功能LT 优化过程中的图表第⼆章优化的光线和光线图背景：为何通过光线进⾏优化？例1：优化⼀个椭圆反射器主要步骤汇总细节步骤更多应⽤第三章噪声优化函数背景：关于噪声优化函数选择正确的优化引擎例2：LED 功率平衡光管关于pikups步骤汇总（70/30 功率平衡）细节步骤（70/30 功率平衡）例3：⼀致性的例⼦⽹格细节更多功能例4：使⽤选择引擎进⾏优化第⼀章开始优化的基本概念这⼀章我们将要学习⼀些关于优化的基本概念⽬录什么是照明设计? (1)什么是优化？ (1)照明系统优化有何特别LT 优化的特别功能LT 优化过程中的图表什么是照明设计?照明设计意味着以下⼏件事，包括基于审美因素的选择和设计；这可能⽐理解为发光设计要好。
照明设计是⼀个技术问题，是为了确定需要的光源的组合（通常在光学软件的帮助下），其他组合以及他们的位置来得到想要的光分布。
基于这⼀性能，分布是指照度、亮度或光强（或他们的辐射当量），可能包含特殊考虑（例如CIE ⾊坐标）。
这⾥有⼀个典型的⽬标分布，特殊表⾯或者区域的照度⼀致性，或者根据强度曲线定义的⾓度分布。
另外还有功效要求，即是到达照明区域的所有可探测的光功率或光通量所占的百分⽐。
组件和要求在初始设计阶段，光源可以被定义为点光源或扩展光源（通常使⽤⾓度和空间分布来近似的模拟物理分布），或者更多的细节光源模型可以使⽤，基于光源组件的物理模型，或者基于测量数据。
组成可以是反射⾯、透镜、有光滑表⾯的塑胶块、⽑⾯或粗糙的表⾯、或其他的光学或机械组件。
这些组件具有⼀定的尺⼨、位置、放置的⾓度、材料属性（如反射系数、吸收系数、体散射），⾯属性如⾦属镀层或⾯散射，⾯的形状从简单的平板到复杂的样条或者⾮球⾯。
组件和整个系统可能具有⼀定的对称，如旋转或双向对称，这些需要特殊的外形设计，或者可能没有对称需求。
LightTools 用于背光模组设计
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莎益博设计系统商贸（上海）有限公司 Cybernet CAE Systems (Shanghai) Co., Ltd.
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结构元件几何特性
• 参数定义方式
– 定值 – 多项式 – 列表
• 定义途径
– 示意图(直观简单)
用以定义定值参数
– 树状列表
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控制系统设计仿真
技术支持
ＣＡＥ教育培训
用户技术培训
机械结构分析
应用顾问
系统集成
HDI/PCB设计服务
光 学检测
客户化开发
及设计优化
电子电路 设计与仿真
新药开发 生命工程
纳米技术
IT解决方案
业务流程管理 会议系统（Ｗｅｂ会议）
反信息泄漏解决方案
知识创新
建筑与 土木工程
IT资产管理 网络安全
远程数据管理
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背光模组简介
基本部件： • 导光板（light guide） • 光源：CCFL 或LED
其它部件： • 增亮膜（BEF） • 散射膜 • 反光板
光源和反射器
微结构
反光板
增亮膜
散射膜 导光板
lighttool在背光设计上的应用
先搞个序言天气冷大家多穿点衣服。
今年气候比较异常，感冒病毒变种显著增多。
千万不要在这个时候感冒，否则，你可能会是下一种猪流感的创始人。
如果别人家破人亡了，你要记得，那是你干的。
关于背光源信息显示如今这个社会有很多种信息显示技术，其中一些被用于照明显示。
我们今天所广泛使用的平板显示是基于LCD显示技术的，它通常都需要一个叫做背光源的照明系统。
这一章我们将通过一个简单的例子来介绍背光源设计，这个过程中可能会占用一部分内存。
一个背光源系统的大体结构如下图所示：·Light source（光源）。
正如这篇文章中的例子里，光源通常都是一个带有反射镜的冷阴极射线管（CCFL）。
而对于小型的显示器则一般使用一个到多个LED。
·Rectangular light guide（矩形导光板）。
它通常被人们叫做导光管，用来传输从边缘光源发出的用于照明液晶板的光线。
·Additional layers（增光板）。
许多背光系统利用显示器前面的散射或者增光装置（BEF）来适当的改变光照的均匀性和角度。
这个设计的重点在于把光线传输到垂直于原来的传播方向，这样就可以更好的为导光板上面的LCD液晶板提供照明。
这里有许多种传输方式，其中一些将会在backlight tutorial（背光指南）中描述和示范。
其中最主要的两种方式是印刷式输出（paint dots）和模型化输出（3D texture）。
不过这两种输出方式都依赖于lighttools中的property zone。
设计一个数字图像显示器在这篇文章的例子里，我们假定一个廉价的数字图像显示设备。
它由一个照明范围为3.5×5 inch（88.9×127mm）组成，附带一个存储记忆卡槽，这样你可以利用它来显示存储在一个数码相机里或个人电脑里的数字照片。
对于这些图片，控制操作等等，它具有充分的处理能力。
这个例子里不打算介绍这个设备里的包装，电源，处理器等器件，只是尽量简洁的描述显示器。
lighttools背光源设计实例
IntroductionBacklights are used for compact, portable, electronic devices with flat panel Liquid Crystal Displays (LCDs) that require illumination from behind. Applications include devices as small as hand-held palm pilots and as large as big-screen TVs. Goals for backlight design include low power consumption, large area with small thickness, high brightness, uniform luminance, and controlled viewing angle, either wide or narrow. To achieve these challenging design goals with a cost effective and timely solution, it is necessary to use computer-aided optical design tools to expedite the design. This paper describes fea-tures in ORA’s LightTools® illumi-nation design and analysis software that enable the development of state-of-the-art backlight designs. Optical Design and Analysis Tools for BacklightsIllumination or lighting systems take light from one or more sources and transform it in some way to produce a desired light distribution over an area or solid angle. Illumination design software must be able to model the geometric and optical properties of different types of light sources and transforming elements, and it must also be able to evaluate the paths of light using optical ray tracing through the model to calcu-late the final light distribution.The light distributions are calculatedusing Monte Carlo simulations tocalculate illuminance, luminance, orluminous intensity over the desiredareas and/or angles. Rays are startedfrom random locations and direc-tions from the source(s), tracedthrough the optical system, and col-lected on receivers. Illuminance canbe calculated for rays collected onsurface receivers and intensity forrays collected on far field receivers.By defining a luminance meter forsurface receivers, the spatial orangular variation of luminance canbe calculated from that surface.In some cases, it may be importantto analyze the chromaticity of a dis-play. The spectral energy distribu-tion of the sources (such as LEDs)can be specified. The output of CIEcoordinates, together with corre-lated color temperature (CCT),quantifies the colorimetric behaviorof the display. An RGB photorealis-tic rendering of the display outputcan also be generated. All of theseanalyses are available in LightTools.Aspects of backlight displays makeparticular demands on illuminationanalysis software. As will be dis-cussed, the means by which light isextracted from a backlight relies oneither dense patterns of paint dots orpatterned microstructures. Model-ing microstructure arrays in particu-lar can result in extremely largemodel sizes if created explicitly as aCAD model. LightTools providesthe capability to define arrays of 3Dtextures that ray trace and renderaccurately but are not explicitly con-structed as part of the geometricmodel, thereby resulting in muchsmaller model sizes and much fasterray tracing.A second aspect of backlight analy-sis involves ray splitting and scatter-ing from the surfaces of the lightguide. Because Monte Carlo simu-lations are used to analyze the illu-mination performance, a potentiallylarge number of rays must be tracedto get sufficient accuracy for com-parison of designs. It is most effec-tive to trace rays that carry most ofthe flux. This can be achieved byusing probabilistic ray splitting totrace the paths with the most flux,and allowing use of aim areas orsolid angles for scattering surfaces todirect scattered light in “important”directions (i.e., toward the displayobserver).What is a Backlight?A typical backlight consists of alight source, such as a Cold CathodeFluorescent (CCFL) or Light Emit-ting Diodes (LEDs), and a rectangu-lar light guide, which is also referredto as a light pipe. Other elementsthan can be used include a diffuser,which enhances display uniformity,and a brightness enhancement film(BEF), which enhances displaybrightness.The light source is usually located atone edge of the light guide to mini-mize the thickness of the display.Edge lighting typically uses totalinternal reflection (TIR) to propa-gate light along the length of the dis-Optical Design Toolsfor Backlight Displaysplay. Figure 1 shows a schematic ofa typical backlight design.The backlight designer has severaloptions for modeling light sources inLightTools. CCFL sources of differ-ent shapes (e.g., straight, L-shaped,U-shaped, or W-shaped, shown inFigure2) can be rapidly definedusing the Fluorescent Lamp CreationUtility. Reflectors for the lamp canbe defined using a variety of Light-Tools geometric primitives, such ascylinders, elliptical troughs, andextruded polygons; reflectorsdefined in CAD systems may also beimported via standard data exchangeformats (IGES, STEP, SAT andCATIA).If LEDs are used, the designer canchoose the desired LED model frompre-stored catalogs of models fromAgilent,LumiLeds, Nichia, orOsram.Once the light is directed into theside of the light guide, the problembecomes extracting the light out ofthe light guide perpendicular to thedirection of propagation.As shown in Figure 3, the availablepower is highest at the source end ofthe light guide and falls off withincreasing distance from the source.To obtain uniform output, the extrac-tion efficiency must increase withdistance from the light source.Developing a light guide that exhib-its the necessary variation in extrac-tion efficiency is one of the primarytasks in designing a backlight.Two extraction techniques can beused. The printed light extractiontechnique uses patterns of paint dotson the bottom of the light guide toscatter light upward and out of thetop of the light guide. The secondtechnique, molded light extraction,relies on TIR from microstructuresor textures patterned on the bottomsurface to redirect light out of the topof the light guide.LightTools supports the design oflight guides via the BacklightDesign Utility. This tool (Fig-ure 4) assists the user in creat-ing the different parts of abacklight. There are optionsfor adding source/reflectorcomponents to the model, BEFmodeling, and setting up areceiver for illumination analy-sis. The main focus of theBacklight Utility is multipletabs for setting up and modify-Figure 2. Fluorescent Lamp Building Blocks ReflectorDiffuser(BEF)Light SourceLight GuideFigure 1. Schematic of a Typical Backlighting extraction mechanisms of differ-ent types.For backlights using the printed light extraction method, the Backlight Utility provides options for linear variation in paint dot size and aspect ratio, as well as linear variation of dot spacing along the length of the light guide. This type of pattern variation will often give a good start-ing point for a uniform display, but is not sufficient to meet the final uni-formity requirements. Additional control of output uniformity can be obtained by allowing non-linear variation of extraction parameters.An approach that gives very flexible control with a minimum of parame-ters is to define the variation of a parameter in terms of a quadraticBezier curve. The LightTools 2D Zone Utility is used to set up nonlin-ear patterns.Figure 5 shows an example using painted light extraction in which three parameters (paint dot width, height, and vertical spacing) are var-ied to create variable extraction behavior.The output uniformity is shown in Figure 6. The slice on the right shows that the average output lumi-nance is constant.The second extraction method,molded light extraction, uses the 3D texture capability in LightTools . The 3D texture feature is designed to ray trace repetitive structures very effi-ciently and store the information very compactly. Models created using explicit geometry can trace more than 30 times slower and have model files more than 100 times larger than equivalent models cre-ated using 3D textures. Three differ-ent basic shapes are available: spheres, prisms, and pyramids (Figure 7).The Backlight Utility provides a means for setting up linearly varying patterns of the microstructure types.2.521.510.50510152025Bezier with Control NetZone NumberFigure 5. Variable Light Extraction Using Quadratic Bezier CurvesFigure 4. LightTools Backlight Design UtilityThe 3D Texture Utility can be used to vary the texture parameters non-linearly using a quadratic Bezier curve. An example where a groove microstructure (modeled using the prism 3D texture) is used as an extraction mechanism is shown in Figure8.The resulting light guide and its per-formance is shown in Figure 9. Optical Calculations for BacklightsTwo of the most important optical quantities for backlight displays are display luminance and illuminance uniformity on the top of the light guide. Calculation of luminous intensity and various colorimetric quantities (CIE coordinates andCCTs) are important as well.LightTools has built-in support forthese calculations and a number offeatures to aid in understanding theresults of the Monte Carlo simula-tions used to generate the data.Monte Carlo simulations are thefoundations of the illumination cal-culations in LightTools. It is gener-ally understood that random numbergenerators are used to pick startingray positions, directions, and wave-lengths to sample the light distribu-tions on the receivers. Theconvergence of the simulations canbe dramatically affected by how the“random” numbers are chosen.Using low discrepancy (Sobol) num-ber sequences, which are not randomat all, can improve the reduction oferror from to 1/N, where Nis the number of rays at the receiver.A comparison of colorimetric resultsusing random number sequences(Figure 10) and Sobol numbersequences (Figure 11) is shown onpage 6. For this case, it would take128,000 rays using a random num-ber generator to equal the accuracyof a 16,000-ray Sobol sequence sim-ulation. It is important to recognizethe simulation convergence speedwhen comparing different software,since it is the speed with which youget to a certain accuracy level, notthe speed it takes to trace a certainnumber of rays, that is important.Receivers in LightTools collect raydata for illumination calculations.1N⁄Figure 7. Sphere, Prism and Pyramid 3D Textures-0.4-0.2-0.00.20.440302010-0.4-0.2-0.00.20.440302010XXY Y403020100.00.10.20.30.4Figure 6. Output Uniformity of Backlight Using Paint DotsThe ray data is collected on data meshes for analysis and display. The user can interactively control the dimensions or number of bins in the data meshes. For a given num-ber of rays on the receiver, meshes with a small number of bins will have low spatial or angular resolu-tion but high relative accuracy (low error), while meshes with a large number of bins will have better reso-lution but lower accuracy (greater error). An error estimate can be dis-played for each bin in a mesh to help the user decide if enough rays have been traced in the simulation to meet the resolution and accuracy neces-sary to assess the design(Cassarly,W.J., Fest, E.C., andJenkins,D.G., 2002). If more raysare needed, the user may interac-tively continue the simulation untilthe goals are met.An important aspect of backlightanalysis involves ray splitting andscattering from the surfaces of thelight guide. The nature of the lightguide is that a ray can bounce aroundthe inside of the light guide numer-ous times prior to becomingabsorbed or exiting the guide. If aray is split into a transmitted andreflected part for each surface inter-action, an extremely large number ofsplit rays result, most of which carrylittle energy, thereby slowing theanalysis. An example of this isshown in Figure 12, which showsthe many paths of a single startingray due to beam splitting.A simulation was run where 2000rays were started from the sourceand, due to ray splitting, 277,948rays were collected on the receiver(Figure 13). Because most of therays reaching the receiver had littleenergy, the error for the result was42%.If, instead, one traces the ray proba-bilistically, with the probability of a-0.4-0.2-0.00.20.440302010-0.4-0.2-0.00.20.440302010XXY Y403020100100200300400 Figure 9. Light Guide Performance with Groove MicrostructureBezier with Control NetZone Number0.350.30.250.20.150.10.05010203040XFigure 8. Definition of a Groove Microstructureray transmitting or reflecting deter-mined by the Fresnel loss coeffi-cients or scattering properties at the surface, the bulk of the ray tracing time will be spent following the flow of the energy in the system, thereby speeding analysis. The results of a simulation where 200,000 rays were started from the source are shown in Figure 14. In this case 118,969 rays reached the receiver with an error estimate of 6% for the calculation. The probabilistic ray trace mode reduced the error in the calculation by 7x and, at the same time, reduced the calculation time by 42%.Finally, diffusers are sometimes used above the top surface of the light guide to improve the angular unifor-mity of the display. Because diffus-ers spread rays over a wide angle, few rays would be scattered into the luminance meter aperture, and cal-culating the luminance normal to the display as measured by a typical luminance meter would require an extremely large number of rays. LightTools provides for aim areas or aim cones to be associated with scat-tering surfaces to allow the user to indicate where the scattered ray sam-ples should be directed. This is a form of importance sampling and is another method for improving the convergence of a Monte Carlo simulation.Figure 15 shows a luminance meter and a backlight with a diffuser with-out an aim cone. Two thousand rays were traced from the source, and the luminance meter collected 40 rays, as shown by the raster plot of spatial luminance.The value of importance sampling can be seen in Figure 16, whichshows the same case but with an aim cone added to the diffuser. The aim cone is matched to the acceptance angle of the luminance meter aper-ture. When a ray is incident on the diffuser, LightTools will generate the scattered ray (with the flux into the aim area determined appropriately based on the full angular distribution of the diffuser model) into the aim cone, so that the luminance meter collects all of the scattered rays, thereby improving the convergence of the simulation. In this case, of the 2000 rays started, 1416 rays (71%) were collected by the luminance meter.Figure 11. Colorimetric Calculations using Sobol SequenceSobol: 16,000 raysFigure 12. Light Guide Traced with Ray SplittingFigure 10. Colorimetric Calculations using Random NumberRandom: 16,000 raysAdditionalConsiderationsBacklights are widely used with Liq-uid Crystal Displays (LCDs), which are polarizing components. The capability to model polarizing com-ponents such as linear polarizers and quarter wave plates and evaluate their effects via polarization ray trac-ing can be critical to the success of an analysis. LightTools provides simple linear polarizer and retarder models, as well as specification of polarization components by their Jones or Mueller matrices. The polarization ray tracing feature,which the user can enable when needed, tracks the polarization state of the ray as it propagates using a Stokes vector.It is often necessary to treat compo-nents with optical coating with vari-ous transmission, reflectance, and polarization properties. Coatings are defined in LightTools in terms of their performance, which is often the only information available to the user. The average or the individual S or P values of reflectance and transmittance can be specified interms of any two of the following parameters: angle of incidence, wavelength, X position, or Y posi-tion. A utility to convert coating stack definitions into the LightTools performance coating format is also available.While most backlights use printed or molded extraction techniques, other approaches are possible. One is to use scattering from particles in the light guide itself. If the particle sizes and density are controlled appropri-ately, Mie scattering from the parti-cles can efficiently extract light from the light guide (Tagaya, et al., 2001:6274). LightTools can simu-late volume scattering according tothe Mie theory for spherical particlesFigure 15. Spatial Luminance for Diffuser without Aim ConeFigure 13. Results of Ray Splitting SimulationFigure 14. Results of Probabilistic Ray Trace3280 East Foothill Boulevard, Pasadena, California 91107Telephone: (626) 795-9101 FAX: (626) 795-0184E-mail: service@ Web site: or according to a user defined angu-lar distribution.Exporting completed optical designs to CAD systems is often a necessary step toward manufacturing the light guide. Support of standardexchange formats such as STEP, SAT, or IGES is needed to accom-plish this. In the case of molded extraction designs, this also requires that the 3D texture definitions of the molded features be translated into explicit geometry for the dataexport, because data exchange stan-dards support the transfer of explicit geometry only. LightTools supports the standard formats and can option-ally export files with 3D textures converted to explicit geometry so that the entire backlight is repre-sented in the exchange file.SummaryThe field of backlight design contin-ues to evolve rapidly in response to market demand for better perfor-mance and reduced costs. This evolution is supported by the devel-opment of illumination design soft-ware with features specifically intended to reduce the design cycle time for new backlight development. Key features in LightTools address-ing model creation and size, ray trace and simulation time, and calcu-lation of a wide range of optical parameters relevant to the design of backlights have been identified and demonstrated.Version 5.0 of LightTools , available in 2004, will add noise-tolerant illu-mination optimization to the features aimed at backlight designers. This will allow light extraction patterns, which maximize power and unifor-mity, to be determined automati-cally.ReferencesCassarly, W. J., E. C. Fest, D. G. Jen-kins, “Error estimation and smooth-ing of 2D illumination andchromaticity distributions,” SPIE Proc ., V ol. 4769, 2002.Tagaya, A., M. Nagai, Y . Koike, K. Yokoyama, “Thin Liquid-Crystal Display Backlight System with Highly Scattering Optical Transmis-sion Polymers,” Applied Optics-OT , Vol. 40, Dec. 2001.Figure 16. Spatial Luminance for Diffuser with Aim Cone。
LightTools 在LED背光设计中的应用-北大深圳研究院
LightTools在LED背光设计中的应用金鹏1，叶浩21.北京大学深圳研究生院2.莎益博设计系统商贸（上海）有限公司摘要：在背光的设计中，一个主要的目标和挑战是保证在垂直于光的传播方向上提升光的利用效率。
在背光模组中，是通过导光板来实现这一过程的，设计的关键就在于找到一种合理的网点分布以获得均匀的亮度分布。
利用光学软件模拟可以自动优化这一过程从而简化设计流程。
关键词：背光模组；导光板；LightTools；自动优化中图分类号：文献标识码：The application of LightTools in LED backlights design（Peng Jin; Shenzhen Graduate School, Peking UniversityHao Ye; Cybernet CAE Systems（Shanghai）Co., Ltd）Abstract：In the backlight design, a major goal and challenge is to ensure that light efficiency has been enhanced in the direction that is perpendicular to the propagation direction of light. In the backlight module, this process is achieved through the light guide plates. the key of the design is to find a reasonable distribution of nodes to obtain uniform brightness distribution. Optical software can automatically optimize and simplify this design processKeywords：backlight module; light guide plate; LightTools; automatic optimization1 引言近年来液晶显示器（LCD）获得迅速发展，并逐渐以主流产品出现在显示市场，相应的，作为LCD显示的核心技术之一的背光源技术也得到了很大的发展【1】。
lighttools 背光设计例
LightTools®的操作介面
功能選單 控制台視窗
系統導覽
3D 設計視窗 屬性對話框
偏好設定導覽
視窗導覽 指令列 錯誤訊息窗
8
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可編輯的COM介面
• LightTools® 可由 COM 介面與其它軟體來結合
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選用 LightTools® 的原因
• LightTools 提供給不同習性的工程師不同的平台
– 工學院相關工程師可透過 GUI 來設計 – 理學院相關工程師可藉由 API/COM 來設計
照明分析的基本架構
光源 接收器 光學系統
Monte Carlo 計算
分析圖表
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設計流程
• 不同於傳統的設計流程。 • 傳統與軟體設計的差異：
– 實際量測 V.S. 模擬值。 – 經驗 V.S. 數值統計。 – 人腦 V.S. 電腦。
3D Object Source Receiver 3D Texture Design NG Analysis OK Manufacture
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3D實體模型
• 以實體物件來表達
放射狀排列
放射狀多項式排列
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Bezier Curve排列
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内容概要
•背光模组的定义与构成
•设计目标与设计方法
•参数设置与优化
•实际案例学习(仪器仪表)
背光模组的定义
•一般构成
–导光板
•
通常其材料为塑料
•注射成型或印刷式的网点（导光板下表面）–光源和反射罩
•（典型光源CCFL and LED ）
–其他常用的光学元件
扩散片(可提高均匀性)反射片
•一些元件能否被使用取决于它的尺寸大小和成本以及其它要求
Schematic of a typical backlight design
Light source Light guide
Diffuser
Reflector
Appliqué
Transparency
主要设计目标
•
在垂直光的传播方向上提升光的利用效率
Light Source
Preferred direction of light extraction
Direction of light propagation
Light guide
Light extraction from a light guide
设计过程: 均匀性
•光能量的传播是随导光板的长度变化的
-出光的提取效率要随导光板的长度的增加而增加•改变光提取效率的方法：
-改变网点密度，网点大小, 网点排布间距
Distance from the source
Available power
Extraction efficiency
Uniform output
背光网点设计
•网点模型：印刷式的或注射成型的网点
在背光设计中经常用到这两种网点来获得亮度均匀的背光
•
最佳的设计参数是优化后得到的网点密度分布
Pattern Generator
+CAD
Illumination Software
Output
OK
Unacceptable
优化过程
通过不断反复调整网点参数进行优化,可以得到最终最佳的亮度与均匀性。
-可以通过做样品或软件模拟来完成
光线追迹后输出模拟
结果
对比输出结果与初始
要求
网点参数设置计算新的网点
更新模型
完成
OK
Not OK
网点参数的确定
–为避免产生莫尔条纹，每个区域网点的密度是不一样
的
网点参数确定方法:
–定义网点密度为二维网格值
–定义网格值
•网点的大小为变量
•网点的数量和大小都为变量
假设给定网点大小与形状
通过计算在一个区域内变化网点的数量，得到想要的网点密度
–网点密度的变化应该是缓慢而平滑的–人眼对突变是很敏感的，对渐变却不敏感
变化网点数量的其他方法
–分子动力学方法–多联骨牌法
Mosaic Structure with
Observable
Rectilinear Substructure Smooth Variation with
Observable
Rectilinear Substructure
Smooth Variation with
Sinusoidal Shifts
假设给定网点位置排布
–经常用的排布一般为六角形
通过计算在一个区域内变化网点的大小通过计算在一个区域内变化网点的大小，，得到想要的网点密度
–出光的效率和网点排布的密度是成比例的
Mosaic Structure using Hexagonal Pattern Smooth Variation using Hexagonal Pattern Smooth Variation using Rectilinear Pattern
网点可以在位置的附近移动偏移网点可以在位置的附近移动偏移，，进行随机的变化, 但并不会重叠
–
也可以对网点的大小进行
随机控制
Dither X,Y=1,0Dither X,Y=0,1Dither X,Y=1,1
Dither X,Y=0,0Dither X,Y=.2,.2Dither X,Y=.5,.5
光线追迹与模拟评估
此商业照明软件可以对背光进行设计模拟评估
–
运用蒙特卡罗随机光线追迹的方法来进行光度计算和模拟–模拟结果的精确度取决于光线追迹的数量和分辨率的高低
高分辨率低精度低分辨率高精度
高分辨率高精度--更多的光线
--
模拟评估
可以使用优化函数进行模拟可以使用优化函数进行模拟，，比较输出结果与要求比较输出结果与要求，，进行评估-可使用优化函数限定统计噪声的最小值
•
当达到设计目标时可以中止优化函数•可增加光线的数目
MF = ∑W i 2(V i -T i )2
W i = Weight of i th MF item V i = Current Value of i th MF item T i = Target of i th
MF item
Luminance
with 10,000 Rays
Luminance
with
1,000,000 Rays
MF = ∑W i 2(V i + ∈i -T i )2MF = ∑W i 2(V i -T i )2 +Noise
网点优化
•BPO 通过改变网点的间距和大小来达到设计的要求
•网点优化可以是2维的平面网点也可以是3维的网点
•我们可以定义个接收面来接收并计算背光板表面的亮度和
照度
BPO 自动优化网点的过程
•BPO 提供有效的优化网点的过程方法
案例1: 印刷式导光板的网点优化
在开始的时候使用均匀的印刷式网点进行优化
得到合理的网点参数
Small Source
(e.g., LED)
2D Display
案例2: 注射成型网点的优化
–
网点大小相同，对排布的位置做优化处理来提高光的利用效率
–这个例子是使用注射成型的网
点进行优化
LED
Start
Final
Texture Density Output
案例3: 两个LED, 非对称排布
•使用注射成型的网点排布
•两个LED
–LED 采用非对称排布
LEDs
Start
Final
Texture Density Output
案例4: 两个LED, 对称排布
•使用注射成型的网点排布
•两个LED
–LED 采用对称排布
LEDs
Start
Final
Texture Density Output
Setup
Bitmap Appliqué
Side View
Top View
LED
Texture
Acrylic Light Pipe
Blue Filter
on kph Appliqué
•如下位图是作为优化的目标
illuminance in
the black
regions
Optimization Results
15 minutes
2.33Ghz processor
100,000 rays/iteration Iteration 1
Iteration 2
Iteration 3
Iteration 4
Iteration 5
Iteration 6
•
模拟结果
Illuminance Chart (1M rays) PhotoRealistic Rendering (100M rays)亮点
边缘照明不足
•需要新的目标区域设定
全覆盖整个
面积
原有仪表盘结构新的仪表盘结构
•最后的结果
Photorealistic Rendering (100M rays)
结论
•网点的优化和模型设置及参数类型选择有紧密联系•介绍了用LightTools 进行设计和分析的一个汽车仪
表盘背光的例子。