应用近红外高光谱成像预测三文鱼肉的水分含量

应用近红外高光谱成像技术实现三文鱼肉水分含量的快速无损检测。采集来自不同部位的三文鱼肉共90个样本的高光谱图像,提取样本感兴趣区域(ROI)的平均光谱。随机取60个样本作为建模集,其余30个样本作为预测集。分别采用偏最小二乘回归(PLSR)和最小二乘支持向量机(LS-SVM)对全波段和水分含量建立相关性模型,并对预测集样本的水分含量进行预测。再用一种新的变量提取方法random frog选择特征波长,并基于特征波长分别建立水分检测的PLSR和LS-SVM模型。特征波长模型的预测精度虽然稍逊于全波段模型,但是仅用12个变量代替了全波段的151个变量,大大简化了模型,更便于实际应用。PLSR和LS-SVM特征波长模型的预测相关系数(Rp)分别为0.92和0.93,预测均方根误差(RMSEP)分别为1.31%和1.18%,取得了满意的结果。研究表明,近红外高光谱成像与化学计量学方法结合可以准确预测三文鱼肉的水分含量,为鱼肉品质的快速监测提供重要的参考。     

干贝水分含量可视化检测方法的研究

水分含量影响干贝的口感、质地等品质特征,而且与其贮存期密切相关。应用高光谱成像与检测技术结合化学计量学方法,实现干贝水分含量的快速检测。实验采用高光谱成像系统采集380~1 030nm波段范围内的高光谱图像,采集得到6个不同干燥时期共90个干贝样本高光谱图像。提取所有样本感兴趣区域的平均光谱数据,采用连续投影算法(SPA)和权重回归系数法(Bw)分别提取了7个和4个特征波长。基于所提取的特征波长和全波长分别建立光谱数据与水分含量的偏最小二乘回归(PLSR)模型,三种模型分别是SPA-PLSR,Bw-PLSR和PLSR。建模集和预测集相关系数都高于0.95,预测均方根误差都低于10%,三种模型均获得了较好的预测效果,都能很好地预测干贝的水分含量。在所有模型中,SPA-PLSR模型具有较少的波长变量和较高的预测能力(97.28%),因此本文基于SPA-PLSR模型,采用伪彩色图像编程技术实现了干贝图像上每个像素点的水分含量的可视化预测。结果表明,高光谱成像技术结合特征波长提取算法可用于干贝水分含量分布的可视化检测。     

基于高光谱成像技术的三文鱼肉水分含量的可视化研究

提出了一种利用高光谱成像技术检测三文鱼水分含量并实现其可视化的新方法。采集不同水分含量的共100个鱼肉样本的高光谱图像,并提取样本感兴趣区域(ROI)的平均光谱。75个样本用于建模集,采用连续投影算法对原始光谱提取特征波长,利用提取的特征波长替代原始光谱,采用PLS建立预测模型,对25个预测集样本的水分含量进行预测,预测决定系数(R2)为0.904,预测均方根误差(RMSEP)为1.169%,获得了满意的预测精度。最后,用所建模型对预测集图像上每个像素点的水分含量进行预测,利用Matlab语言编程,三文鱼肉表面不同部位的水分分布采用不同颜色表示,进而实现三文鱼肉水分含量的可视化。结果表明,高光谱成像技术与化学计量学结合可以准确预测鱼肉的水分含量,与图像处理方法结合可以实现预测时间的可视化,能形象、直观地展示出鱼肉的水分含量分布情况,为实现水产品加工的自动化奠定了基础。     

可见-近红外光谱分析技术对鱼油掺假定量快速无损检测方法研究

对掺入不同含量大豆油和菜籽油的鱼油进行鱼油掺假含量的可见-近红外光谱(Vis-NIR)研究。向3个不同品牌鱼油中分别掺入不同比例的大豆油,另外3个不同品牌中分别掺入不同比例的菜籽油,共获得300个样本。对所采集样本的光谱数据分别采用原始光谱,以及平滑,变量标准化(SNV),多元散射校正(MSC),一阶求导和二阶求导等预处理算法进行处理后,建立偏最小二乘回归(PLSR)模型。基于全波段光谱的鱼油中大豆油和菜籽油掺假含量预测的最优模型分别为全波段PLSR模型和MSC-PLSR模型,其预测相关系数(Rp)分别达到0.938 6和0.959 3。进一步采用连续投影算法(SPA)分析鱼油中大豆油和菜籽油掺假样品的光谱,并分别获得了11个和15个光谱特征波长变量。基于特征变量的PLSR模型的Rp分别为0.941 2和0.932 6。试验研究表明,可以采用Vis-NIR技术实现对鱼油掺假物含量的检测。     

应用高光谱图像检测鱼肉挥发性盐基总氮含量研究

鱼类产品的新鲜程度研究一直是重要的课题,其中挥发性盐基总氮（TVB-N）是一项重要指标,该指标已列入我国食品卫生标准, 一般在低温条件下, 鱼类挥发性盐基氮的量达到30 mg/100 g时,即认为是肉质变质的标志。传统的物理检测方法不能够实现定量检测,化学检测法则耗时长,且需要专业人员进行破坏式检测。为了克服传统光谱检测技术无法检测分析外部空间属性的缺点,该实验采用波长范围在900～1 700 nm高光谱成像结合化学计量法实现了三文鱼的TVB-N含量检测。首先对从市场买的新鲜三文鱼按照背面和反面（腹部）进行分割处理,背面和反面（腹部）再10等分,每条三文鱼制作成20个样本,一共100个样本,其中75个样本用于校正集,25个样本用于预测集。然后用高光谱成像系统采集三文鱼鱼样本的光谱数据,再通过蒸馏法测定三文鱼TVB-N的含量,并建立其理化值样本,然后分别采用最小二乘支持向量机（LS-SVM）和偏最小二乘（PLS）模型对100个样本光谱全波长数据进行三文鱼TVB-N建模分析。LS-SVM模型和PLS模型预测决定系数(R2)分别为0.918和0.907,预测均方根误差(RMSEP)分别为2.312%和2.751%。为了进一步提高运算效率和优化模型,对全谱数据利用连续投影算法（SPA）提取到8个特征波长（956,1 013,1 152,1 210,1 286,1 301,1 397和1 464 nm）,基于8个特征波长分别建立SPA-LS-SVM和SPA-PLS模型,模型预测决定系数(R2)分别为0.903和0.901,RMSEP分别为2.761%和2.801%,SPA-LS-SVM模型的结果优于SPA-PLS。最后SPA-LS-SVM模型因其可靠性和有效性而被选择为最适合TVB-N预测模型,基于图像处理编程技术将高光谱图像中的每个像素转换成相应的TVB-N值并以不同颜色表示,实现了三文鱼肉TVB-N含量的可视化,可以很形象的表达三文鱼的TVB-N的含量分布情况。实验说明,可利用高光谱成像技术预测三文鱼的TVB-N含量预测,这为水产品的自动加工和分类奠定了基础,渔业可以从高光谱技术中获益。     

应用近红外高光谱成像技术预测甘蔗可溶性固形物含量

为了探究应用近红外高光谱成像技术对甘蔗内部可溶性固形物(SSC)预测的可行性,试验样本选择三种不同品种中的240个甘蔗节作为研究对象。通过高光谱成像系统获取甘蔗节的近红外光谱信息和图像信息,并分别探讨了光谱信息和图像纹理信息对甘蔗可溶性固形物预测的可行性。采用最小二乘回归(PLSR),最小二乘支持向量机(LS-SVM)及主成分回归(PCR)建模方法构建甘蔗可溶性固形物的预测模型。比较了连续投影算法(SPA)、无信息变量消除算法(UVE)及区间偏最小二乘(iPLS)特征提取方法对预测结果的影响。实验结果表明:基于甘蔗的光谱信息能实现可溶性固形物的预测,其中偏最小二乘回归模型的建模集和预测集的相关系数分别为0.879和0.843,均方根误差分别为0.644和0.742。通过UVE算法提取105个有效波长所建立的PLSR模型的建模集及预测集相关系数分别为0.860和0.813,均方根误差分别为0.693和0.810。     

基于可见-近红外光谱技术的润滑油含水量无损检测方法研究

研究了基于可见-近红外光谱技术的发动机润滑油含水量快速检测方法。在获取光谱信息的基础上,提出了采用不同的光谱建模方法以提高检测精度和简化分析计算。分别采用主成分分析(PCA)和连续投影算法(SPA)方法进行模型输入变量的提取。SPA最终选择了476,483,544,925,933,938,952,970和974nm共9个波长为最优变量。基于SPA选择的变量,分别应用偏最小二乘回归(PLSR)和多元线性回归(MLR)建模。效果均优于全波段PLSR模型和PCA-PLSR模型。说明SPA选择的有效变量能够包含最重要的全波段光谱信息,同时可以去除无用的信息变量。为了进一步提高检测效果,采用LS-SVM分别基于SPA选择后的有效变量和全波段光谱进行建模。两个模型的预测确定系数(Rp2)均在0.9以上。SPA-LS-SVM的效果要优于全波段LS-SVM模型的效果。SPA-LS-SVM模型的Rp2达到了0.983,剩余预测偏差(RPD)值为6.963。表明可见-近红外光谱可以用于发动机润滑油含水量的检测。     

LS-SVM的梨可溶性固形物近红外光谱检测的特征波长筛选

为提高梨可溶性固形物含量(soluble solids content,SSC)的近红外光谱模型的精度和稳定性,以160个梨样品为实验对象,分别对原始光谱、多元散射校正(MSC)和标准正态变量变换(SNV)处理后的光谱,经无信息变量消除算法(UVE)挑选后,再结合遗传算法(GA)和连续投影算法(SPA),筛选梨可溶性固形物的近红外光谱特征波长。将筛选后的波长作为输入变量建立梨可溶性固形物的最小二乘支持向量机(LS-SVM)模型。结果表明经过SNV-UVE-GA-SPA从全波段3112个波长中筛选出的30个特征波长建立的梨可溶性固形物LS-SVM模型效果最好,该模型的预测集相关系数(Rp)和预测均方根误差(RMSEP)分别为0.956和0.271。该模型简单可靠,预测效果好,能满足梨的可溶性固形物含量的快速检测,为在线检测和便携式设备开发提供了理论基础。     

基于可见近红外光谱技术的车蜡品牌无损鉴别方法研究

探讨了可见-近红外光谱技术快速无损识别不同品牌车蜡的可行性。实验一共获得104样本,其中40个样本(建模集)用于建立模型,剩余64个样本(预测集)被用于独立验证建立好的模型。基于五种不同品牌车蜡的可见-近红外光谱分别建立了线性判别分析(linear Discriminant Analysis,LDA)和最小二乘支持向量机(least square-support vector machine,LS-SVM)模型。基于两个算法的全波段光谱模型的预测集正确率分别达到了84%和97%。进一步采用连续投影算法(successive projections algorithm,SPA)算法从751波段中选取了7个特征波段(351,365,401,441,605,926和980nm)。基于SPA选择的变量建立LS-SVM模型,准确率依然保持在97%。说明SPA选择的特征波段包含了对于车蜡品牌鉴别最重要的光谱信息,而大多数无用信息则被有效剔除。将SPA与LS-SVM算法的车蜡识别模型在保证正确率的基础上,还可以大大降低模型计算复杂程度,说明该模型能快速准确的从车蜡可见-近红外光谱中提取有效信息,并实现车蜡品牌的无损鉴别。     

特征变量优选在苹果可溶性固形物近红外便携式检测中的应用

为实现苹果可溶性固形物(SSC)的便携式快速检测,利用环形光纤探头和微型光谱仪搭建便携式苹果可溶性固形物光谱采集系统,结合无信息变量消除(UVE)、遗传算法(GA)、竞争性自适应加权(CARS)算法筛选基于偏最小二乘(PLS)的苹果可溶性固形物的近红外光谱特征波长。另外,采用反向区间最小二乘支持向量机(BiLS-SVM)和GA算法优选基于LS-SVM的特征波长变量,分别建立所选特征波长和全波段的PLS模型和LS-SVM模型。试验结果表明,经过GA-CARS算法从全波段1 512个波长中筛选出的50个特征波长建立的PLS模型效果最好,其预测相关系数和预测均方根误差分别为0.962和0.403°Brix。利用该检测装置结合GA-CARS筛选的特征波长,可有效简化苹果可溶性固形物近红外便携式检测模型并提高模型的预测精度,为进一步构建便携式苹果可溶性固形物检测设备奠定了基础。     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.