Relative spectral response calibration using Ti plasma lines

This work introduces the branching ratio(BR) method for determining relative spectral responses,which are needed routinely in laser induced breakdown spectroscopy(LIBS). Neutral and singly ionized Ti lines in the 250–498 nm spectral range are investigated by measuring laser-induced micro plasma near a Ti plate and used to calculate the relative spectral response of an entire LIBS detection system. The results are compared with those of the conventional relative spectral response calibration method using a tungsten halogen lamp, and certain lines available for the BR method are selected. The study supports the common manner of using BRs to calibrate the detection system in LIBS setups.

Online calibration of laser-induced breakdown spectroscopy for detection of heavy metals in water

In order to reduce the fluctuation of LIBS detection spectrum of liquid sample,the full-spectrum sum method and the internal standardization method is adopted,using an equal-RSD normalization algorithm to calibrate the detection spectrum.Experiment result shows that the full-spectrum sum method reduced the RSD of parallel samples of Cd and Cr to 9.4% and 11.06% from 28.32% and 31.93% respectively,yielded better overall calibration than the singleelement internal standardization approach,thereby suggesting that the former method is convenient and effective for online calibration of LIBS for detection of aqueous heavy metals.

Calibration and data restoration of light field modulated imaging spectrometer

A light field modulated imaging spectrometer （LFMIS） can acquire the spatial-spectral datacube of targets of interest or a scene in a single shot. The spectral information of a point target is imaged on the pixels covered by a microlens. The pixels receive spectral information from different spectral filters to the diffraction and misalignments of the optical components. In this paper, we present a linear spectral multiplexing model of the acquired target spectrum. A calibration method is proposed for calibrating the center wavelengths and bandwidths of channels of an LFMIS system based on the liner-variable filter （LVF） and for determining the spectral multiplexing matrix. In order to improve the accuracy of the restored spectral data, we introduce a reconstruction algorithm based on the total least square （TLS） approach. Simulation and experimental results confirm the performance of the spectrum reconstruction algorithm and validate the feasibility of the proposed calibrating scheme.

Adsorption of Three Commercial Dyes onto Chitosan Beads Using Spectrophotometric Determination and a Multivariate Calibration Method

A simple and rapid analytical method for the simultaneous quantification of three commercial azo dyes—Tartrazine (TAR), Congo Red (CR), and Amido Black (AB) in water is presented. The simultaneous assessment of the individual concentration of an organic dye in mixtures using a spectrophotometric method is a difficult procedure in analytical chemistry, due to spectral overlapping. This drawback can be overcome if a multivariate calibration method such as Partial Least Squares Regression (PLSR) is used. This study presents a calibration model based on absorption spectra in the 300 - 650 nm range for a set of 20 different mixtures of dyes, followed by the prediction of the concentrations of dyes in 6 validation mixtures, randomly selected, using the PLSR method. Estimated limits of detection (LOD) were 0.106, 0.047 and 0.079 mg/L for TAR, CR, and AB, respectively, and limits of quantification (LOQ) were 0.355, 0.157 and 0.265 mg/L for TAR, CR, and AB, respectively. Quantitative determination of the three azo dyes was performed following optimized adsorption experiments onto chitosan beads of mixtures of TAR, CR and AB. Adsorption isotherm and kinetic studies were carried out, proving that the proposed PLSR method is rapid, accurate and reliable.

Empirical Line Method Using Spectrally Stable Targets to Calibrate IKONOS Imagery

By using speetrally stable targets, the empirical line （EL） method was tested to correct the multispectral IKONOS imagery acquired over Putuo Mountain, Zhejiang, China. A series of calibration targets, which were spectrally stable over time, were selected to establish the linear predicted equation. Subsequently, a series of spectrally stable validation targets were selected to assess the accuracy of the equations. And, validation targets, which were speetrally unstable over time, were used to test the feasibility of using the EL method to calibrate the archival remotely sensed data. Ground reflectance measurements for each target were made using an ASD FieldSpec spectroradiometer. A Trimble GeoXTTM GPS unit with sub-meter accuracy was used to estimate the target position accurately. Linear regression equations for four tKONOS bands were derived. The coefficients of determination for the blue, green, and red bands were all greater than 0.9800 and it was 0.9697 for the near infrared band. It was concluded that reasonable results could be obtained by using speetrally stable targets.

多级冗余强干扰下医用三维力传感器数据的自动挖掘方法

针对医用三维力传感器容易受电磁场等外部环境的影响,产生大量相似特征数据,导致其输出紊乱信号,降低传感器控制精度和测量速度的问题,提出一种多级冗余强干扰下三维力传感器数据挖掘方法。根据角度标定理论采集三维力传感器冗余数据;引入相似度指数函数计算冗余因子,获取三维力传感器冗余数据活跃度,完成数据冗余分类;通过差值去噪算法高性能过滤三维力传感器冗余数据;利用谱聚类算法构建拉普拉斯矩阵,剔除冗余数据,实现三维力传感器数据自动挖掘。仿真结果表明,所提方法在多级冗余强干扰下的三维力传感器控制精度为96.54%,测量速度为0.61 ms,能量消耗为0.26 kcal。由此证明,所提方法的控制精度高、测量速度快、传输效果优,能够满足机器人辅助手术过程中的力反馈控制需求。

基于距离修正的小目标中波红外光谱辐射测温方法

对高速运动的远距离空间目标而言,温度是表征其工作状态与性能的重要参数之一。准确获取目标的温度对判别其运动状态和预测其态势发展等具有重要的参考价值。目前常用的面目标或点目标的处理方法,在小目标的辐射特性测量中将不再适用,而光谱探测增加了目标在波长维度的可分辨信息,可以准确获取目标能量随波长的分布情况,为目标温度的反演提供了可能,极具应用潜力。无狭缝光谱仪可以降低对空间目标的跟踪和稳定精度的要求,具有结构简单、帧频高和响应速度快等特点,在天文观测和航天器观测等方面具有较高的应用价值。对目标红外辐射特性测量的光谱定标模型进行了分析,确定了红外探测器像元线性响应模型中的主要参数。为了减小成像距离对测温精度的影响,提出了一种基于距离修正的目标温度反演模型,提高了测温精度,符合实际工程实践应用中的精度需求,对红外辐射光谱测温具有一定的指导意义。

红外光谱成像仪非线性定标温度点选择方法

为充分校正红外探测器响应非线性,解决大动态范围下使用多点法定标出现的温度点数冗余的问题,提出一种基于相对标准差阈值划分的定标温度点选择方法。使用标准差法将响应曲线划分为多段,采用最小二乘法线性拟合得出定标系数,并通过数据反演、合并和压缩,获得红外光谱成像仪各个谱段最终定标温度点。仿真结果表明,对于模拟的单光谱通道探测器非线性响应,相同划分条件下(相对标准差1%),对比常规二分法,所提方法可将温度点数由22个降低至14个;相同温度点数条件下(20个),对比均匀划分,所提方法可将非线性度最大值由1.06%降低至0.40%。对于模拟的17个光谱通道,取10个定标温度点时,非线性度均值小于1%。红外相机实测实验结果表明,利用该方法确定的定标温度点,定标后非线性度均值达到0.48%。该方法可有效减少定标温度点数,降低载荷在轨定标资源要求。

间接型光谱成像仪相对光谱响应函数标定方法

间接型光谱成像仪通常采用面阵探测器作为光电转换器件,探测器像元间光谱响应的不一致性会导致采集到的目标光谱失真,所以标定和修正像元间光谱响应的不一致性是提升间接型光谱成像仪光谱辐射测量精度的重要手段.本文以干涉光谱成像仪为例,分析了系统像元间相对光谱响应不一致对目标光谱辐射测量准确性的影响,提出了基于傅里叶变换调制定标源的间接型光谱成像仪全系统相对光谱响应函数测量方法,并建立了相对光谱响应函数标定的数理模型.仿真分析结果表明,理想无噪声时,像元间1%的相对光谱响应不一致性会对复原光谱造成1.02%的相对误差,经过相对光谱响应校正后,不同行复原光谱的相对误差降至0.08%.最后,仿真分析了相对光谱响应不一致性在不同光谱信噪比下的校正效果.该方法可提高间接型光谱成像仪光谱测量的准确性和一致性.

黑体涂层宽温区红外光谱发射率特性研究(内封面文章)

为了研究高发射率黑体涂层的宽温区红外辐射特性,基于两种发射率测量装置测量了应用于不同温度场景的JSC-3和GR两种涂层宽温区3~14μm内的光谱发射率。其中JSC-3和GR涂层的测量温度范围分别是室温~1000℃和室温~150℃。分析了两种涂层光谱发射率与温度之间的关系以及不同角度下方向光谱发射率的变化。实验结果表明:宽温区内JSC-3和GR涂层在8~14μm的光谱发射率分别优于0.96和0.97,且光谱发射率保持稳定,变化量分别小于0.01和0.003。两种涂层在0°~30°内的方向光谱发射率均具有较好的一致性,变化量均小于0.005。最后利用积分球反射法得到了两种涂层在室温下3~14μm内的连续光谱发射率数据,实现了两种涂层在宽温区宽波段内的光谱发射率数据覆盖。

可见光光谱辐射计波长标定技术研究

为了解决可见光光谱辐射计波长标定过程中存在的峰值偏移、较弱特征谱误判及人工谱线识别等问题,采用自适应阈值法和差分法完成对特征谱检测与识别,利用最小二乘法和拉格朗日插值法确定波长和像元的关系,进行了理论分析和实验验证,获得最佳波长标定方程。结果表明,特征谱根据谱线强度依次被检测并识别出来,以404.6565 nm、435.8335 nm、546.0750 nm、579.0670 nm为基准的拉格朗日插值法得到的方程为最佳波长标定方程,其残差标准差仅为3.2747×10^(-13)nm,波长标定误差分布在±0.2 nm范围内。自动谱线检测方法及谱线识别方法提高了波长标定效率,避免了噪声误判和谱线识别错误现象,为其它光谱类仪器的波长标定提供了参考。

基于日盲紫外光辐射特性的非共光轴紫外成像仪集成研制

基于日盲紫外波段放电发射光谱特性和紫外光(ultraviolet,UV)辐射传输特性,集成研制可见光与紫外非共光轴结构的日盲紫外成像仪。首先,利用放电发射光谱测量试验平台,获得针-板模型和瓷绝缘子沿面放电的日盲紫外波段发射光谱。紫外成像仪采用非共光轴双光路结构设计,根据测得的放电发射光谱选定了日盲紫外滤光片,并基于紫外光辐射传输特性确定了通光口径、系统焦距和80%弥散斑半径等紫外光学系统技术指标。然后,利用仿射变换模型和加权平均法进行了可见光与紫外图像融合系统设计,集成后仪器样机的最小紫外灵敏度为2×10^(-10)μW/cm^(2)。最后,利用紫外检测结果一致性校准方法,建立了紫外检测辐射传输模型,对集成研制的紫外成像仪进行了一致性校准。

Design of on-board calibration methods for a digital sun sensor based on Levenberg–Marquardt algorithm and Kalman filters

Digital sun sensor is one of the most important sensors used in the Attitude Determination System(ADS)of the satellite.Due to the harsh environmental conditions that exist in the space,various distortions may occur in the sun sensor optical system that lead to the reduced accuracy of this equipment.So,it is necessary to recalibrate the optical parameters of the aforementioned sensors.For this purpose,first a novel attitude independent error model is proposed for the SS-411 sun sensor that includes the central point of the CCD array,installation error,filter thickness and sensor misalignment.So,the mutual interfaces between the sensor parameters are considered in the developed model.In order to extract the sensor parameters,a nonlinear optimization technique called the Levenberg–Marquardt is applied to the developed model as a batch algorithm.In addition,the Extended Kalman Filter(EKF)and the Unscented Kalman Filter(UKF)have been utilized as sequential strategies.It will be shown that by considering a worst case of variation amount for sensor parameters,an accuracy improvement of about 17°is achieved by the developed calibration algorithms.Comparison between the developed algorithms represents that UKF has higher accuracy,shorter time convergence but higher computational load.

高光谱紫外辐照度仪CCD电路系统的设计及测试

为了在地面获得高信噪比的太阳直射紫外光谱辐照度,选用紫外敏感型线阵CCD探测器,研发了高光谱紫外辐照度仪原理样机。设计了CCD电路系统,讨论了电源电路、驱动电路、模拟前端电路以及CCD驱动时序的工作原理与设计方法,并在实验室利用标准灯光源测试了CCD电路系统的非线性和信噪比。结果表明,在340 nm波段下,CCD探测器接收信号约为饱和信号的80%时,系统信噪比超过400。最终,将测试好的CCD电路系统与光机模块装调并进行了波长定标,光谱范围覆盖280~400 nm,实现了对室内光源的紫外高光谱测量,验证了CCD电路系统设计的合理性和可行性。

多光谱星敏感器的辐射定标与光谱反演

为实现星敏感器对未知空间光环境的测量,提出一种将宽谱段多光谱滤光片装置于星敏感器中的设计,所采集的星图可覆盖星点信息与空间光环境光谱信息,并以此为基础设计了光谱响应定标、辐射定标的实验方案与空间光环境辐亮度分布反演算法。实验结果表明,反演的光环境辐亮度与实测值较为符合,该方法能根据单张星图实时便捷地估算星敏感器应用空间的光环境,可为后续星敏感器的设计优化和观星窗口的选择提供依据。

光谱吸收型气体分析仪校准技术研究

光谱吸收型气体分析仪适合在开放场所应用,而可调谐半导体激光吸收光谱(TDLAS)气体分析仪具有不受粉尘、视窗、环境参数和背景气体交叉干扰,反应速度快和精度高等优点,近年来广泛地应用于恶劣工况的现场监测,但在线校准溯源技术的相关研究甚少。从TDLAS吸收光谱模型出发,分析了TDLAS分析仪测量原理和分类,提出采用标准浓度腔来校准TDLAS气体分析仪的方案。该方案提供了一种浓度均匀、量值稳定且背景单一的标准气体环境,成功对TDLAS分析仪进行了校准。经校准实例证明,方法可行,测量不确定度接近于标准气源的不确定度,最好可达1.1%。

光波导输入的双通道同步定标虚拟成像相位阵列光谱仪

激光频率梳定标的虚拟成像相位阵列光谱仪有潜力同时实现超高光谱分辨率与波长定标精度,对于天文光谱探测有重要意义。然而,现有的研究工作中,虚拟成像相位阵列光谱仪采用常规的双通道光纤输入模式,在受环境干扰时,两个通道的同步性较差,相对漂移严重,从而降低了光谱仪的重复性定标精度。为解决该问题,提出一种以光波导作为输入器件的双通道虚拟成像相位阵列光谱仪,利用波导通道之间相对稳定的特性,实现更高水平的同步定标精度。通过对不同环境下光谱仪的稳定性进行研究得出,在相似的测试条件下,波导输入的虚拟成像相位阵列光谱仪的重复性定标精度明显优于光纤输入时的定标表现。

大气典型α二羰基化合物的光谱探测方法和外场应用

乙二醛和甲基乙二醛是大气环境中两种最典型的α二羰基化合物,其浓度变化是大气VOCs氧化过程和反应活性的重要表征,对于研究大气VOCs氧化反应具有重要意义。大气乙二醛和甲基乙二醛具有浓度极低、寿命短、活性较强,使其浓度的准确探测具有一定的挑战性,导致外场环境的监测结果较少,缺乏大气化学反应机理分析的研究。对于α二羰基化合物的探测先后发展出化学衍生化法、质谱法等,能够有效地实现气体浓度监测,而技术也存在一定的局限。随着光学技术的进步,针对大气α二羰基化合物发展了一系列的光谱测量手段,比如差分吸收光谱、腔增强吸收光谱、激光诱导磷光、傅里叶红外光谱等技术,具有非接触、探测限低、灵敏度高、时间分辨率高等特点。综述了乙二醛和甲基乙二醛的光谱测量技术现状和发展趋势,对方法的原理、技术要点、优缺点等进行了详细的说明,列举了技术的器件参数、反演算法、探测限等关键特征,并对其国内外相关应用予以介绍。针对高活性α二羰基化合物的标定需求,详细说明并对比分析了现有条件下常用的气流稀释法、待测物溶液温控起泡器法、加热法、大气反应法等气体标定方法。对基于光谱技术的大气α二羰基化合物外场观测实验进行汇总分析,对实验条件、浓度结果、主要结论等予以总结,表明光谱技术是乙二醛和甲基乙二醛探测的有力手段,列表说明了浓度变化与一次污染排放、VOCs氧化、二次有机气溶胶生成等反应的相关性;重点讨论了甲醛、乙二醛、甲基乙二醛混合比率,得出不同环境下的混合比数值范围,表明RGF在BVOCs环境下数值较低,高混合比可能预示着人工源VOCs的影响。

Seya-Namioka类型真空紫外光谱系统的研制和性能测试

为了满足磁约束核聚变领域的杂质测量要求,研制了一套Seya Namioka真空紫外光谱仪。该光谱仪的主要部件是可调宽度的入射狭缝、凹面光栅和探测器。光谱仪的光通量通过可调节宽度的入射狭缝来调节,入射狭缝宽度可以在10~1000μm范围内调节。分光元件选用线密度为1200 lines·mm^(-1)的凹面全息光栅。光栅表面涂有铝(Al)和氟化镁(MgF2),以提高衍射效率。光栅的可使用波段为50~460 nm,针对其中的50~250 nm波段进行光路优化设计。选用深度制冷背照式电荷耦合器件(CCD)作为光谱仪的探测器。通过转动光栅转台旋转光栅来改变衍射角,实现50~250 nm范围内的光谱观测。基于凹面光栅的参数,确定了具体光路,并分析了波长随光栅旋转角度的变化关系及不同波长处的线色散率。基于凹面光栅成像理论,对系统的光谱分辨率进行了计算分析。通过分析不同出射臂下的光谱分辨率,确定最优出射臂为205 mm。在出射臂为205 mm、入射狭缝为20μm的情况下,分析了入射狭缝宽度、像素大小、像差和衍射极限对光谱分辨率影响。结果表明:衍射极限对光谱分辨率的影响最小,基本上可以忽略不计,出射狭缝的宽度对光谱分辨率有较大贡献,大约为0.09~0.10 nm,且在50~250 nm波长范围内缓慢增加。分析了不同入射狭缝宽度(10~80μm)下光谱分辨率,光谱分辨率随狭缝宽度呈递增趋势,变化范围为0.10~0.32 nm,当狭缝宽度达到80μm时,光谱分辨率已经变的较差,不利于高分辨线辐射光谱测量。在实际测量中,应该综合考虑光通量和光谱分辨率需求。采用低压汞灯和微波等离子体光源进行波长校准和性能测试。基于零阶光谱和汞灯的特征光谱HgⅠ(185 nm)对光谱仪进行了波长标定。通过HgⅠ(185 nm)谱线的高斯拟合分析,得到仪器在185 nm处的光谱分辨率为0.1243 nm,与理论计算值接近。通过实验与理论计算对比不同出射臂下的HgⅠ(185 nm)光谱分辨率,验证了仪器在出射臂为205 mm处获得最佳光谱分辨能力。利用微波等离子体放电光源装置对光谱仪进行了进一步的性能测试,基于光源发射的氮、氧和氦线的测量,验证了光谱仪在50~250 nm波长范围内具有良好的探测能力。

基于多角度多光谱相机的相对辐射校正方法分析

多角度多光谱相机(Directional Multi-Spectral Camera,DMC)由5台相机组成,每台相机单独成像,这种成像方式导致其立体成像过程中多相机间辐射响应很难保持一致性。为实现各个视角相机及每片CCD的辐射响应一致,文章提出了多相机全局色差标定法,并与直方图在轨统计法和偏航定标法对DMC影像的辐射校正效果进行了对比。其中几种方法的相机间影像的辐射校正效果比较显示,多相机全局色差标定法校正的5个相机的影像颜色更接近,且均匀地物的相对辐射校正精度更高;CCD片间影像的校正效果比较显示,直方图统计法和多相机全局色差标定法校正的CCD片间影像都呈现颜色均衡,基本无色差,且相对辐射校正精度在3%以内。综上,说明多相机全局色差标定法更适用于校正DMC的辐射一致性问题。