文献翻译——简易光谱分析仪的设计

第1页外文文献资料Designofasimplespectrumanalyzer1.1.summaryTheTAOSTCS230isasmall,highlyintegratedcolorsensingdevicepackagedinaclearplastic8-pinSOIC.Itreports,asanalogfrequency,theamountofshortwave(blue),mediumwave(green),longwave(red),andwideband(white)opticalpowerincidentontothedevice.Itcanbeusedinavarietyofcolorsensingapplications.Detailsofthedevicecanbefoundinitsdatasheet.ThiswhitepaperdetailstheconceptsandcalculationsinvolvedincolorsensingusingtheTCS230.WewillusetheColorCheckerchartasanopticalstimulustoworkthroughanumericalexampleofcolorsensing.Thechart,depictedinFigure1-1,ismanufacturedanddistributedbyGretagMacbeth.Thechartmeasuresapproximately13inchesby9inches(330mmby230mm);itcontains24coloredpatchesarrangedina6by4array.Figures1-2through1-5overleafshowthespectralreflectanceofthepatchesineachofthefourrowsofthechartthatis,thefractionofincidentlightthatisreflected(withrespecttoanidealdiffusereflector),asafunctionofwavelengthfrom350nmto750nm.Figure1-1TheColorCheckercontains18coloredpatchesanda6-stepgrayseries.第2页Figure1-2ColorCheckerspectra,toprow.Figure1-3ColorCheckerspectra,secondrow.Figure1-4ColorCheckerspectra,thirdrow.第3页Figure1-5ColorCheckerspectra,bottomrow(neutralseries)Figure1-6ConesensitivitiesofconephotoreceptorsareshownTheshortwave-sensitivephotoreceptorsaremuchlesssensitivethantheothertwotypes.Theresponsesofthemediumwaveandlongwavephotoreceptorshaveagreatdealofoverlap.Visionisnotsensitivetotheprecisewavelengthofthestimulus:Whatattersisopticalpowerintegratedundereachresponsecurve.1.2.IntroductiontocolorvisionPhotoreceptorcellscalledconesintheretinaareresponsibleforhumancolorvision.Therearethreetypesofconecells,sensitivetolongwave,mediumwave,andshortwaveradiationwithintheelectro-magneticspectrumbetweenabout400nmand700nm.Becausetheconesensitivitiesareveryroughlyinthepartsofthespectrumthatappearred,green,andblue,color第4页scientistsdenotethecelltypesas,and,theGreeklettersforr,g,andb.(TodenotethesensorsR,G,andBwouldwronglysuggestaclosercorrespondence.)EstimatesofthespectralresponseoftheconetypesaregraphedinFigure1-6above.Lightinthephysicalworldcanbecharacterizedbyspectralpowerdistributions(SPDs).Coloredobjectscanbecharacterizedbyspectralreflectancecurves,suchasthoseoftheColorChecker.However,visionisinsensitivetotheexactwavelengthofastimulus:Accordingtothemoderntheoryofcolorscience,allthatmattersistheintegralofopticalpowerunderneatheachresponsecurve.Thatthereareexactlythreetypesofconecellsleadstothepropertyoftrichromaticity:Threecomponentsarenecessaryandsufficienttocharacterizecolor.Somepeoplemightusethephrase“colorassensedbytheeye,”butIcon-siderthatqualifiertoberedundantatbest,andmisleadingatworst:Colorisdefinedbyvision,sothereisnoneedtousethequalifyingphrase“assensedbytheeye,”ortousetheadjectivevisiblewhenreferringtocolor.1.3.OverviewofCIEColorimetryThespectralresponsesoftheconecellsthatIgraphedinFigure1-6wereunavailabletoresearchersinthe1920s.Researchersatthetimeusedpsychophysicalexperiments,suchasthefamouscolormatchingexperiment,toteaseoutthedata.TheCIEistheinternationalbodyresponsibleforcolorstandards.In1931,thatorganizationadoptedthecolormatchingfunctionsdenotedx(),y(),andz(),graphedinFigure1-7.第5页Figure1-7CIE1931,2color-matchingfunctions.Acamerawith3sensorsmusthavethesespectralresponsecurves,orlinearcombinationsofthem,inordertocaptureallcolors.However,practicalconsiderationsmakethisdifficult.Theseanalysisfunctionsarenotcomparabletospectralpowerdistributions!WeightingaphysicalSPDundereachofthesethreecurves(thatis,formingthewavelength-by-wavelengthproduct),andsummingtheresults,formsatripleofthreenumbers,denotedX,Y,andZ.Incontinuousmathematics,threeintegralsneedtobecomputed;indiscretemath,amatrixproductissufficient.TheX,Y,andZtristim-ulusvaluescharacterizecolor.Theyarelinear-lightquantities,propor-tionaltoopticalpower,thatincorporatethewavelengthsensitivityofhumanvision.TheYvalueisluminance,whichisordinarilyexpressedinunitsofcandelapermetersquared(cdm-2).Ifyouaremeasuringreflectance,thereflectedtristimulusvaluesdependuponthespectralcharacteristicsoftheilluminant,andtheiramplitudesscalewiththepoweroftheillumination.Relativeluminanceistheratioofreflectedluminancetotheluminanceoftheillumination;itisalsoknownastheluminancefactor.第6页Figure1-8SPDsofvariousilluminantsaregraphedhere.IlluminantA,showninorange,isrepresentativeoftungstenlightsources;itisdeficientinshortwavepower,andmaycauseerrorsinsensingbluecolors.ThebluelinegraphstheSPDofaNichiawhiteLED.Thereisapeakintheblueportionofthespectrum:Uncorrected,thesensorwouldreportexcessivebluevalues.TheotherfourlinesrepresentCIEstandardilluminantsC,D50,D55,andD65.Inmanyapplications,tristimulussignals(includingluminance)scalewiththeillumination,andareotherwiseuninterestinginthemselves.Whatismoreinterestingistheratiosamongthem,whichcharacterizecolordisregardingluminance.TheCIEhasstandardizedtheprojectivetransformationofEquation1,inthemargin,totransformX,Y,Zvaluesintoapairofx,ychromaticitycoordinatesthatrepresentcolordisregardingluminance.Thesecoordinatesaresuitableforplottingintwodimensionsonachromaticitydiagram.1.4.IlluminationAnonemissiveobjectmustbeilluminatedinordertobevisible.TheSPDreflectedfromanilluminatedobjectisthewavelength-by-wave-lengthproductoftheilluminantsSPDandthespectralreflectanceoftheobject.Beforelightreachestheeye,theinteractionamonglightsourcesandmaterials第7页takesplaceinthespectraldomain,notinthedomainoftrichromaticity.Toaccuratelymodeltheseinteractionsrequiresspectralcomputations.WhenapplyingtheTCS230,attentionmustbepaidtothespectralcontentoftheilluminationandtopoten-tialinteractionbetweentheilluminationandthesamplestobesensed.Generally,thelessspikythespectra,thebetter.Figure1-8graphsseveralilluminants.Yourapplicationmayinvolvesensingcolor,inwhichcasetheprecedingdescriptionapplies.However,someapplicationsoftheTCS230involvenotsomuchestimatingcolorasseenbytheeyebutrathersensingphysicalparametersassociatedwithopticalpowerinthevisiblerange.Insuchapplications,toapproximatethevisualresponsemaynotbethebestapproach:Itmaybemoreeffectivetotakeamoredirectapproachtoestimatingtheparametersoftheunderlyingphysicalprocess.1.5.TheColorCheckerEquippedwithknowledgeofhowspectraarerelatedtocolors,theplottingofchromaticitycoordinates,andthedependenceofcolorsuponillumination,wecanreturntotheColorChecker.GretagMac-bethdoesntpublishorguaranteethespectralcompositionofthepatchesoftheColorChecker.However,nominalCIEX,Y,Zvaluesarepublished.ThepatchesinthebottomrowoftheColorCheckercontainneutralcolors;thenumericnotationsinthelegendsofFigure1-5reflectonetenthofthelightness(L*)valuesofthosepatches.Thespectragraphedonpages2and3representthephysicalwave-length-by-wavelengthreflectanceofthepatches.Thesespectralreflec-tanceshavebeenmeasuredbycolormeasurementinstrumentcalledaspectrophotometer.Ifyouhadaccesstoalightsourcehavingperfectlyevendistributionofpoweracrossthevisiblespectrum,thenthereflectancecurvesgraphedherecouldsimplybescaledtorepre-sentthereflectanceinyourapplication.Practicallightsourcesdonothaveperfectlyevenspectraldistributions,socompensationisneces-sary:Youmustcomputethewavelength-by-wavelengthproductoftheilluminantsSPDwiththespectralreflectanceofthechart.WewillfirstcalculatetheCIEX,Y,Zvaluesfromthechart.(These第8页valuesshouldagreewiththefiguresprovidedbyGretag.)ThenwewillcalculatetheR,G,BvaluesthatwillbedetectedbyaTCS230.TocalculateCIEX,Y,Z,wetakethe313matrixrepresentingthecolormatchingfunctions(CMFs)oftheCIEStandardObserver,andperformamatrixproductwith31spectralresponsevaluesascorrectedforillumination.ThisproducestheX,Y,Ztristimulusvalues.Whenchromaticitycoordinatesx,yarecomputedfromX,Y,ZthroughtheprojectivetransforminEquation1,thenplotted,thechromaticitydiagraminFigure1-9results.Thehorseshoe-shapedfigure,closedatthebottom,containsallcolors:Everynon-negativespectraldistributionproducesanx,ypairthatplotswithinthisregion.Thelightly-shadedtriangleshowstheregioncontainingallcolorsthatcanbeproducedbyanadditiveRGBsystemusingsRGB(Rec.709)primarycolors.Thisregiontypifiesvideoanddesktopcomputing(sRGB).ThepointsplottedinFigure9arethecolorsoftheColorChecker.Whiteandgrayvaluesareclusterednearthecenterofthechart.Figure1-9CoordinatesofColorCheckerpatchesaregraphedontheCIEx,ychromaticitydiagram.Thehorseshoeenclosesallcolors;thetriangleenclosesthecolorsthatcanberepresentedinvideo(Rec.709)andindesktopcomputing(sRGB).2.1.TheTCS230Figure2-1showstheresponsesofthefourchannelsoftheTCS230.The第9页blackcurveshowstheresponseoftheunfilteredsensorelements.Thered,green,andbluecurvesshowtheresponsesofthelongwave-sensitive,mediumwave-sensitive,andshortwave-sensitiveelementsrespectively.AsImentionedonpage5,theCIEmodelofcolorvisioninvolvesinte-gratinganSPDundertheX(),Y(),andZ()colormatchingfunc-tions(graphedinFigure7),producingX,Y,andZvalues.TousetheTCS230toestimatecolorweperformananalogouscalculation,butusingtheTCS230sensitivityfunctionsinsteadoftheCIECMFs:WeintegratetheSPDundertheTCS230ssensitivitycurves,andproduceR,G,andBvalues.ThedeviceR,G,andBvalueswilldependuponseveralfactors:thespectralcontentoftheilluminant,thespectralreflectanceofthesample,thespectralattenuationofanyinterveningopticalcomponents(suchasthelens),andfinally,thespectralresponsefunctionsoftheTCS230.Thevariousspectralphenomenaaremodelledbycomputingwavelength-by-wavelengthproducts.Figure2-1TCS230spectralsensitivitiesaregraphedhere.Thered,green,andbluechannelsaregraphedinthecorrespondingcolors;thegraylinereflectsthesensitivityoftheclear(unfiltered)channel.BecausetheseresponsesaredifferentfromtheCIEstandardobserver,thevaluesreportedbytheTCS230arenotcolorimetric.However,suitablesignalprocessingyieldscolorinformationthatissufficientlyaccurateformanyindustrialapplications.OwingtothefactthattheTCS230issensitivetoinfraredlight(havingwavelengthsabove700nm),andthefactthatmostlightsourcesproducepower第10页intheinfraredregion,typicalapplicationsincludeanIRcutfilterinfrontoftheTCS230.Figure11overleafshowstheresponseofatypicalIRcutfilter.ToformamoreaccurateestimateofcolorrequiresprocessingtherawTCS230R,G,andBvaluesthroughalinear33matrixwhosecoeffi-cientsareoptimizedwithrespecttothespectrumoftheilluminant,thespectralresponseofinterveningopticalcomponents,andtheresponsecurvesoftheTCS230.Thedataprocessingoperationcanberepresentedinmatrixformasfollows:x=MtEq2Thesymboltrepresentsathree-elementvectorcontainingthedevicevaluescapturedfromacolorpatch.Mrepresentsthe33colorcorrectionmatrixthatwewillapplytothesevaluesthroughmatrixmultiplication,denotedbythesymbol.ThesymbolxrepresentstheresultingvectorofestimatedX,Y,Zvalues.Wecanusematrixnotationtosymbolizeprocessingasetofthreecolorpatchesatonce,byarrangingthethreesetsofdevicevaluesintosuccessivecolumnsofa33matrixT.SuccessiverowsofTcontainred,green,andbluedatarespectively.UponmatrixmultiplicationbyM,thecolumnsoftheresultingmatrixXcontainXYZvaluesofthesuccessivesamples;therowsofXcontainX,Y,andZvaluesrespec-tively.Oneequationexpressesthemappingofthreepatchesatonce:X=MTEq3GivenamatrixTwhosecolumnscontainthreesetsofdevicesamples,andamatrixXcontainingthecorrespondingsetofthreeidealXYZtriples,thereisauniquematrixMthatmapsfromTtoX.ItisfoundbycomputingthematrixinverseofT,thencomputingthematrixproduct(bypremultiplication)withX:M=XEq4Theresulting33colorcorrectionmatrixMexactlymapstheeachofthechosenthreesetsofdevicevaluestothecorrespondingsetoftris-timulusvalues.Itisnotnecessarytoinvertmatricesatthetimeofsensing!ThematrixMcanbecomputedinadvance,baseduponthesamplesthatareexpected第11页tobepresentedtothesensorintheintendedapplication.Toprocessthreedevicevaluesuponsensingasample,allthatisnecessaryiscomputationofthematrixproductofEquation3.Acolorcorrectionmatrixthatproducesgoodresultsacrossmorethanthreesamplescanbecomputedthroughanumericaloptimizationprocedure.Whenthisisdone,noparticularsampleislikelytomapexactlytoitsidealtristimulusset,butalinearmatrixcanbeconstructedthatminimizestheerroracrossarangeofsamples(wheretheerrorismeasuredinaleast-squaressense).ThecolorcorrectionoperationisstillaccomplishedexactlyasinEquation2.第12页中文翻译稿简易光谱分析仪的设计1.1.概述TAOS公司的TCS230是一个小的、高度集成、8引脚、SOIC封装的色彩传感装置。它以模拟频率的方式输出短波（蓝色）、中波（绿色）、长波（红色）、宽带（白）光功率的事件数量。它可用于各种色彩感应应用领域。该设备的详细资料中可以找到它的数据表。本白皮书详细介绍了色彩感应的概念和使用TCS230参与计算。我们将使用一个光学刺激方案的ColorChecker图表工作，通过检测的色彩数值例子。下图，在图1-1所示，是由GretagMacbeth生产和分配。图表长约13英寸，9英寸（330毫米230毫米），它包含了64阵列安排24色斑。到5背面图2显示了在图表的每一行四个补丁的光谱反射-即入射光被反射的那部分（相对于一个理想的漫反射）作为波长从350功能，纳米到750纳米。图1-1-ColorChecker色补丁包含18个和6步灰色系列第13页图1-2ColorChecker谱，第一行图1-3ColorChecker谱，第二排图1-4ColorChecker光谱，第三行第14页图1-5ColorChecker谱，底排（中性系列）图1-6锥锥光感受器敏感性所示短波敏感的感光细胞远远低于其他两种类型的敏感。中波和长波的感光细胞的反应有很大的重叠。视觉是不敏感，准确的刺激波长：什么是光功率下atters每个响应曲线综合。1.2.色觉简介所谓感光细胞在视网膜视锥细胞是人类色彩视觉负责。内有电磁频谱三种类型的视锥细胞，敏感的长波，中波，短波辐射及约400纳米之间和700纳米。由于锥敏感性在频谱的部分出现红色，绿色和蓝色的很粗糙，色彩科学家记为，以及希腊字母为R，G细胞的类型，和b（为了表示对传感器的R，G，和B将错误建议更密切的对应关系。）的圆锥体的谱反应的估计是在上面绘制图1-6。在物理世界的光，其特征是光谱功率分布（结构化产品说明）。彩色对象，其特征是反射光谱曲线，如在的ColorChecker的。然而，视觉不敏感，对刺激精确波长：根据现第15页代色彩科学理论，最重要的事情是在每个响应曲线光功率积分。这恰有三种视锥细胞类型导致trichromaticity财产：三个组成部分是必要的和足够的特征颜色。有些人可能会用“感觉到的颜色的眼睛，“但我了CON-Sider的限定词是多余的，充其量，误导在最坏的情况：色彩是由视觉定义，所以没有必要使用合格的短语“因为感觉到的眼睛，“或使用的形容词时可见指颜色。1.3.概述Cie的比色法锥细胞，我在图1-6绘制光谱反应无法在20世纪20年代的研究人员。当时的研究人员使用，如著名的配色实验心理实验，以梳理出的数据。在CIE是国际机构，颜色标准。In1931，该组织通过了颜色匹配函数记（）和Y（）和z（），在图1-7绘制。图1-7Cie公司1931年2色彩匹配功能。一个3传感器的相机必须具备以下的光谱响应曲线，或它们的线性组合，以捕捉所有的颜色。然而，实际的考虑作出这一困难。这些分析功能比不上光谱功率分布！加权根据这三个曲线每个物理社民党（即，形成了波长的波长产品），总结的结果，形成了三个数字三倍，记在连续数学的X，Y和Z，三积分需要计算，在离散数学，矩阵产品就足够了。在X，Y和Ztristim-汗国值特征的颜色。它们是线性光量，正比于光学力量，即纳入人类视觉波长的敏感性。Y值是亮度，这是通常在每平方米坎德拉（光碟米-2）为单位表示。如果你是测量反射率，反射的三刺激值取决于对光源的光谱特性，其幅度与规模的照明电源。相对亮度的反射亮度的照明亮度的比值，它也被称为亮度因素。第16页图1-8绘制各种光源结构化产品说明A光源，以橙色显示，钨光源是代表，它是在短波力量不足，可能会导致感应蓝色的错误。蓝线图的社民党的日亚白光LED。有一个光谱的蓝色部分高峰：裸时，传感器会举报过度蓝色值。另外四线代表Cie的，D50的，D55和D65的标准光源。在许多应用中，三刺激信号（包括亮度）与照明规模，并应在其他无趣自己。什么是更有趣的是它们之间的比例，所特有的颜色无视亮度。在CIE有标准化的公式1中的保证金射影变换，将其转化为一对的X，Y和Z值的x，y表示颜色的色度坐标无视亮度。这些坐标在二维色度图上绘制合适。1.4.照明一个nonemissive对象必须是为了照明可见。社民党从一照物体反射的波长是按波长的光源产品的社民党和对象的光谱反射率。光线到达之前光源和材料之间的眼睛，相互作用发生在谱域的地方，不是在trichromaticity域。为了准确地需要这些相互作用的光谱模型计算。当应用TCS230，必须注意对光照光谱内容和电位-TiAl金属间的照明和样品被觉察的互动。一般来说，越尖的光谱，就越好。图1-8图数光源。您的应用程序可能涉及敏感的颜色，在这种情况下，前面的说明适用。然而，一些应用涉及TCS230没有这么多的眼睛所看到的，而是传感在可见光范围内光功率相关的物理参数估计的颜色。在这种应用中，近似的视觉反应可能不是最好的方法：它可能是更有效地采取更直接的方法来估计底层物理过程的参数。1.5.色彩检查第17页如何光谱与颜色相关的知识装备，绘制色度坐标，对照明色彩的依赖，我们可以返回的ColorChecker。GretagMac-Beth没公布或保证的ColorChecker补丁的光谱成分。然而，标称Cie的的X，Y和Z值被公布。在底行的ColorChecker补丁包含中性色，在图1-5中的神话传说中的数字符号反映十分之一的亮度（长*）值的这些补丁。这些光谱反射已测色仪测量tances称为分光光度计。如果你有机会访问光源具有完全的权力分配，甚至在整个可见光谱，反射率曲线则绘制在这里可以简单地扩展到repre，发送应用程序中的反射率。实践没有光源的光谱分布十分均匀，因此补偿neces-萨利：你必须计算与图表的光谱反射的光源的波长社民党按波长的产品。我们将首先从图表计算在CIE的X，Y和Z值。（这些值应同意Gretag提供的数字。）然后我们将计算的R，G，B的，将由一TCS230检测值。为了计算Cie公司的X，Y和Z，我们把313矩阵代表职能的配色在CIE标准观察者（CMFs），并执行一个有31个光谱响应矩阵产品价值为照明纠正。这将产生的x，Y，Z轴三刺激值。当色度坐标，通过投影的x，y是来自的X，Y和Z变换计算公式1，然后绘制，结果如图1-9色度图。马蹄状的人物，在底部封闭，包含所有的颜色：每个非负的光谱分布产生的x，y对本地区范围内的阴谋。拥有轻成荫的三角显示包含所有的地区，可以通过一个附加的RGB使用的sRGB系统（建议709）原色产生颜色。这个地区typifies视频和桌