近紅外光譜原理.

1、s1近紅外光譜原理及應(yīng)用主要內(nèi)容近紅外光譜原理-近紅外光譜與化學(xué)計(jì)量學(xué)近紅外模型的評(píng)價(jià)第一部分近紅外光譜原理什么是近紅外光12,800 cm1 (780 nm)X-射線ML丫射線做波Radio. TV 上 線電波3,960 cm i (2,526 nm)迖紅外娠動(dòng)-!UOQOB3U-原廣核 轉(zhuǎn)變分（轉(zhuǎn)動(dòng)波長度量單位：納米nm與波數(shù)cm1cm _ 10znm800nm _ 800nm1cm=107nm波長800nm轉(zhuǎn)換為cnrnm = 107/cm-1 cm-1 = 107/ nm=12500cm 1振動(dòng)吸收光譜的理論E = Et + Ev + Er + Ee分子能量平動(dòng) 振動(dòng) 轉(zhuǎn)動(dòng)電子運(yùn)動(dòng)輻射

2、光的能屋與振動(dòng)躍遷能量和同時(shí)，輻射光被物質(zhì) 分子吸收。能ht接近ev近紅外光能吊引起分子振動(dòng)能級(jí)的變化， 乂稱振動(dòng)光譜。近紅外光譜產(chǎn)生原理近紅外吸收光譜特征u物質(zhì)在近紅外譜區(qū)的吸收重疊嚴(yán)重.近紅外的合頻振動(dòng)的吸收系數(shù)比中紅外基頻振動(dòng)吸收弱1-5個(gè)數(shù)量級(jí).Water SpectrumcOUBqJosqvWavenumber cm 1不同化合物基團(tuán)在近紅外區(qū)的吸收譜帶Firsi OrftMTaoe RegiiwTtiril (XtHton Fkgtiihoar InfraredLksttd AsyHOD 1OT0IMOX(D1XK17001800BCD2000Z1002200230024002M0

3、33)K2714J仙67Z SM256S6S263WOO4J624354348416?SOO10J 11111 1WOO !91水分、脂肪、蛋白吸收譜帶High watercontent宙脂肪XHigh fat :ontentprotein:ontent近紅外光與物質(zhì)的相互作用吸收 全反射 absorption specula reflectance透射transmitta nee滋（反）射Diffusescatteringreflectance光源單色縉或干涉儀光源單色器或干涉儀樣品檢測R9透漫射式Near-IR Trans-Reflectance (NITR)單色器或干汾儀樣品近紅外的采樣

4、方法透射式Near-IR Transmittance (NIT)漫反射式NearIR Reflectance (NIR)近紅外的分光方法濾光片型光源樣品檢測器濾光片濾光片型儀器的優(yōu)缺點(diǎn)優(yōu)點(diǎn)：1. 制造成本低，推廣面大：2. 體積小，可以便攜。缺點(diǎn)：1. 濾光片的帶寬較寬（一般10nm）。2. 濾光片透光的光譜中心點(diǎn)難以保證。3. 同一波長濾光片的帶寬和透過率難以保證一致。4. 信息最少，只能作為專用儀器。5. 得到的不是連續(xù)光譜，不能對光譜進(jìn)行預(yù)處理（如平滑、求導(dǎo)等）。光柵掃描型狹縫光源光柵挾縫檢測器光柵掃描型B狹縫光源光柵挾縫檢測器光柵掃描型狹縫光源檢測器光柵型儀器的優(yōu)缺點(diǎn)優(yōu)點(diǎn)：1. 結(jié)構(gòu)不

5、復(fù)雜.容易制造。2. 連續(xù)光譜儀.可以作為研究級(jí)儀器。缺點(diǎn)：1. 使用單色器.狹縫的限制使其分辨率和靈敏度不夠高2. 波長準(zhǔn)確度使用外部校準(zhǔn)，加之分辨率低，波長準(zhǔn)確度差（最好為 +/-0. 2nm） o3. 使用單色器對光路要求嚴(yán)格，儀器擴(kuò)展能力受到很大的限制，4. 自然界的雜散光會(huì)影響測試結(jié)果。5. 由于分光需光柵轉(zhuǎn)動(dòng).掃描速度慢。陣列檢測器陣列檢測器陣列檢測器型的優(yōu)缺點(diǎn)優(yōu)點(diǎn)：1. 無移動(dòng)光學(xué)部件，易實(shí)現(xiàn)小型化。2. 掃描速度快.適合現(xiàn)場分析。缺點(diǎn)：1. 分辨率較低2. 一致性比光柵掃描型更難保證。3. 受雜散光影響SampleSourceDetectorGratingMEMS Micro

6、electro mechanical systems 微電子機(jī)械系統(tǒng)SourceTeO2 CrystalSampleDetectorsReferencemonochrom Light (extraordinary Beam)non-scattered Lightmonochrom. Light (ordinary Beam)Mems ChipAOTF acousto optical tunable filter 聲光可調(diào)濾光器RF-InputMichelson InterferometerMovableMirrorBeamsplitterBSourceBeamsplitterDetectorM

7、ovable mirror M2Fixed mirror Ml穹 DetectorS|/WWVWWWW11/WVWVVWVWWWV-C2VC-Fixedmirror MlMovable miiror M2wcm】AxSourcemmmmI tetnr nllx=0L + AxBeamsplitterBeamsplitterDetectorSpcctrumcasc-DetectorFixed mirror MlOftlcil m irdatiua.fKPsSpcxrtruni of 9 Kgl frguciKie,FfcuencyMichelson InterferometerMovableMi

8、rror SourceBeamsplitterDetector傅立葉變換型的優(yōu)缺點(diǎn)優(yōu)點(diǎn)：1. 光通量大，靈敏度高，高信噪比。狹縫2. 高分辨率。3. 咼測昆精度a4. 測量速度快。5. O O O缺點(diǎn):1.平面反射鏡.如果在快速掃描過程中發(fā)生晃動(dòng)和偏轉(zhuǎn).造成干涉信號(hào) 降低，靈敏度下降。Cube-Corner InterferometerPlane Mirrors in a classical Michelson Interferometer Cube-Corner Mirrors in a ROCKSOLID-InterferometerCube-Corner m i r rorsThe RO

9、CKSOLID philosophy is to eliminate possible sources of measurement errors rather than to try to correct for them after the measurement第二部分近紅外光譜與化學(xué)計(jì)量學(xué)朗伯比爾定律Sample右=intensity of reference beamI intensrty of sample beam d sample thickness c concentration c = molar absorptlon coefficientTransmission TAb

10、sorpti on = A=log = Ecd透過率、吸光度與濃度的關(guān)系Transmission (Reflectance)not linearAbsorbanceLog I()linearThe Calibration ModelsB線性冋歸D2O10COOH1200KOO15D018002000曲inmj22002400cc oQuant itat i ve Ana lysis; Regress i on2603BWavelengthConce ntrationThe Calibration Models1一個(gè)波長點(diǎn)a = b + mxC = B0+BI *AC = Con centrat

11、ionBo= Bias (intercept, offset)Bi = Regression Coefficent at wavelength 1A1 = Absorbance at wavelength 1近紅外光譜的重疊The CaIibrat ion Mode Is多元線性冋歸2.兩個(gè)波長點(diǎn)C = B（）+ B * A + B2 * A2*three dimensions !3n個(gè)波長點(diǎn)C = Bo+B| *A| + B?*A 4- + B,* An n+1 dimensions !How to f i nd the bands you need?About how many data

12、po ints are we talking about?Start WL (nm or cm-1)End WL (nm or cm-1)Optical resolutionUseful datapoints11002500101409090400016318909040003215990904000863690904000412739090400022545Optical resolution Dispersive system in cm-1About how many data points are we taIk about?Principle Comp orient Analysis

13、 (PCA)Matr ices and vectorsFactor Analysis of spectraFactor Analysis breaks apart lhe spectral data into the most comm on spectral variati ons (factors, loadings, principal components) and the corresponding scaling coefficients (scores)光譜矩陣載荷dldata matrix:spectra of data pointsscores: loadings:score

14、s for each spectrum ( ) loadings of data points ( )西紅柿雞蛋vs主成分B1 x西紅柿3x鴨蛋3x水0.2 x2x西紅柿2x雞蛋0.1 x 水05x蔥2x西紅柿1 x雞蛋 25x水 0.1 x 蔥Factor Ana lysisBscoresctor 15.216ctor 2-016ctor 31.73E-02ctor 4“ 52E-02ctor 53.17E-02ctor 15.95ctor 20.103ctor 34.97E-04ctor 44.33E-02ctor S5.SSEO3ctor 17.731ctor 20699ctor 33.S7E-04ctor 41.16E02ctor 5-2.04E-02ctor 15.768ctor 20.693ctor 32.97E-02ctor 4-3.76E-03ctor 51.27E02ctor 17.13 ctor 20.441ctor 3-3.75E-02ctor 4-9.54E-03ctor 54.46E-03FaFaFaFaFaFaFaFaFaFaF zFdF FFaFaFaFaFflfactors光譜7.731+-0.699+3.67E-04+-1.15E-02+204E02spectrumReconst