外差式偏振干涉成像光谱技术研究

提出了一种新型的基于Savart偏光镜的外差式偏振干涉成像光谱技术,该技术在偏振干涉成像光谱仪中引入一对平行偏振光栅对,使其得到的干涉图频率与波数相关,具有了波数外差的特点,降低了干涉图频率,从而可利用较少的采样点数实现很高的光谱分辨率.对外差式偏振干涉成像光谱技术的基本原理进行了研究,详细分析了系统光程差、干涉图表达式、光谱分辨率以及光谱复原方法等.最后给出了外差式偏振干涉成像光谱仪的设计实例并进行了计算机仿真模拟,所复原的光谱与输入光谱曲线相符合,验证了方案的正确性.外差式偏振干涉成像光谱仪具有结构紧凑、光通量高、稳定性强、光谱分辨率高的特点,尤其适合超小型高稳定性、高探测灵敏度的高光谱探测应用.     

Optimization of polarization spectroscopy for rubidium D lines

Polarization spectroscopy of the D lines of rubidium atoms is investigated experimentally,especially with different pump powers and cell temperatures.We find that there are four candidate transitions suitable for frequency stabilization,and optimal pump powers and cell temperatures are also presented to obtain a perfect signal with maximal amplitude and slope.The optimal signal is insensitive to the fluctuations of laser power and the temperature,which can enhance the performance of frequency locking.     

Effect of polarization spectroscopy in multitep excitation and ionization of atoms on ionization efficiency

In this peper, the seventeen real motion equation of atoms were shown for the first time inconsiderlng the polarization choices of laser lights. The importance of polarization spectrcoscopy in thedetermination of ionization yields of multi-step excitation and ionization of atoms (MSEIA) wasshown.     

Embryo viability indexing using Raman spectroscopy of spent culture media

ABSTRACT

Embryo viability quantification is an important topic for in vitro fertilization researchers. This study suggests Raman spectroscopy as a candidate method to find an objective measure of embryo viability. Raman spectra of 31 spent embryo culture samples (16 nonpregnant, 15 pregnant) from 31 patients were analyzed with band component analysis. The band area ratio of 902 to 943 cm^?1 was found to be the most discriminatory. These bands are related to glutamine, glycine, proline, aspartic acid, and valine. According to the pregnancy outcome the sensitivity and specificity of Raman analysis were found to be 93% and 77%, respectively.     

The high dependence of polarization resolved laser-induced breakdown spectroscopy on experimental conditions

It is shown that the continuum emission produced by an Al alloy ablated by femtosecond laser pulses is much more polarized than the characteristic lines of elements. A Glan-Thomson polarizer is used in the laser-induced breakdown spectroscopy experiment to investigate the polarization effect. The use of the polarizer at its minimal transmission increases the signal-to-noise ratio. The effects of angle of detection, focal position, and pulse energy on the signal-to-noise ratio are also studied.     

新型偏振干涉成像光谱仪信噪比研究

基于辐射度学、电磁与偏振理论和傅里叶变换光谱学理论，从理论和实验上对超小型稳态偏振干涉成像光谱仪的信噪比进行了深入地分析与讨论.推导出了其信噪比的理论计算公式；采用计算机模拟给出了傍轴条件下信噪比随入射角的变化规律；深入分析了偏振干涉成像光谱仪所特有的偏振化方向对信噪比的影响.在调制度等于0.6，0.7，0.8，0.9，1.0时，给出信噪比随偏振器光轴偏角的变化关系，并给出最优化值.在最优化情况下，采用计算机模拟得出了信噪比随探测器像元数的变化规律，与干涉成像光谱实验结果完全相符.理论与实验结果表明，该偏振干涉成像光谱仪在高调制度的情况下具有高通量、高信噪比的显著特点，适合于航空航天、远距离目标和微弱信号的探测.该研究为新型偏振干涉成像光谱技术的研究和新型成像光谱仪的设计、研制和工程化提供了重要的理论依据和实践指导.     

铁电体中极化长程涨落的光子关联谱实验研究

从极化团簇的随机涨落出发, 利用维纳过程模型, 推导了铁电体中极化长程涨落的弛豫规律以及光强自相关函数所可能的表现形式. 阐述了微观极化团簇的弛豫过程与宏观测量弛豫规律之间的联系. 通过对原有氦氖激光光子关联谱实验装置进行改进, 观测了BaTiO₃和0.71Pb(Mg_1/3Nb_2/3)O₃-0.29PbTiO₃单晶中极化团簇长程涨落在居里点和立方到四方相变点附近的弛豫过程. 在BaTiO₃中发现极化团簇长程涨落在居里点之上4 K存在双弛豫现象, 此现象与其有序无序相变机理相联系. 在Pb(Mg_1/3Nb_2/3)O₃-0.29PbTiO₃中发现极化团簇长程涨落在相变点两侧都存在双弛豫现象. 利用推导的理论结果很好地拟合了实验结果并提取了极化团簇长程涨落的弛豫时间. 两种样品中极化团簇长程涨落的弛豫时间都在相变点出现突变, 并呈现临界慢化现象.     

Nasopharyngeal carcinoma detection by tissue smears using surface-enhanced Raman spectroscopy

Nasopharyngeal carcinoma is one of the most common malignant neoplasms in head and neck. In this work, surface-enhanced Raman spectroscopy technique was used to study the molecular differences between cancerous and noncancerous smear samples which were obtained after clinical biopsy by smearing the tissue on the slides. Principal component analysis combined with linear discriminant analysis provided a sensitivity of 79.4% and a specificity of 81.8% for differentiation between cancerous and noncancerous nasopharyngeal tissue smears. This work provides a good basis for the methodology of nasopharyngeal tissue smear based on surface-enhanced Raman spectroscopy technique and is worth further studying.     

Measurement and calculation of the Q‐branch spectrum of nitrogen using inverse Raman spectroscopy and cw Raman‐induced polarization spectroscopy

The techniques of inverse Raman spectroscopy, Raman‐induced polarization spectroscopy (RIPS), and optical heterodyne RIPS (OHD‐RIPS) are compared by probing the Q‐branch of the nitrogen molecule. The signal is measured employing either a photomultiplier tube (low background level–RIPS) or a photodetector (high background level–IRS and OHD‐RIPS). The measurements are performed using atmospheric mixtures of N₂ Ar with concentrations varying from 0 to 79% N₂. This strategy permits estimation of detection limits using the different techniques. Pump and probe energy levels are varied independently to study signal dependence on laser irradiance. A theoretical treatment is presented on the basis of the Raman susceptibility equations, which permits the calculation of spectra for all three techniques. Calculated Q‐branch spectra are compared with the measured spectra for the interactions of a linearly polarized probe beam with a linearly or circularly polarized pump beam. The polarizer angle in the detection path for OHD‐RIPS has a dramatic effect on the shape of the spectrum. The calculated and experimental OHD‐RIPS spectra are in good agreement over the entire range of investigated polarizer angles. Detection limits using these techniques are analyzed to suggest their applicability for measuring other species of importance in combustion and plasma systems. Copyright © 2007 John Wiley & Sons, Ltd.     

Detection of myocardial viability by low-dose dobutamine Cine MR imaging

The purpose of this work was to test the diagnostic value of dobutamine stress magnetic resonance imaging (MRI) for predicting recovery of regional myocardial contractility after revascularization. Cardiac wall motion abnormalities are due to either non-viable and/or scarred, or viable, but hibernating, myocardial tissue. Dobutamine stress leads to increased systolic wall thickening only in viable myocardium. Twenty-five patients with akinetic or dyskinetic myocardial regions were examined with a Cine FLASH-2D sequence at rest and during dobutamine stress (10 μg/kg/min). Patients were re-examined at rest 3, and in case of persisting wall motion defects, 6 months after revascularization. Criterion of viability was increasing end-systolic wall thickening during stress and/or at follow-up. Akinetic regions related either to the LAD (n = 19) or to the RCA (n = 6) were judged viable if >=50% of the affected segments improved. MR studies were completed in all subjects without arrhythmia or need for early terminations due to symptoms. Sensitivity, specificity, and positive predictive value for the prediction of myocardial viability were 61%, 90%, and 87% for the segment-related analysis, and 76%, 100%, and 100% for the patient-related analysis based on coronary artery distribution, respectively. Dobutamine stress MRI allows to predict global functional recovery of akinetic myocardial regions after revascularization with a high positive predictive value and high specificity.     

Applications of Raman spectroscopy in dentistry part II: Soft tissue analysis

Raman spectroscopy is rapidly moving from an experimental technique for the analysis of biological molecules to a tool for the real-time clinical diagnosis and in situ evaluation of the oral tissue in medical and dental research. The purpose of this study is to identify various applications of Raman spectroscopy, to evaluate the contemporary status, and to explore future directions in the field of dentistry. Several in-depth applications are presented to illustrate Raman spectroscopy in early diagnosis of soft tissue abnormalities. Raman spectroscopy allows researchers to analyze histological and biochemical composition of biological tissues. The technique not only demonstrates its role in the disclosure of dysplasia and malignancy, but also in performing guided biopsies, diagnosing sialoliths, and assessment of surgical margins. Raman spectroscopy is used to identify the molecular structures and their components to give substantial information about the chemical structure properties of these molecules. In this article, we acquaint the utilization of Raman spectroscopy in analyzing the soft tissues in relation to dentistry.     

Raman spectroscopy of alkali halide hydration: hydrogen bond relaxation and polarization

The solute–solvent interaction of salts has a striking impact on various biological and industrial processes but its mechanism remains yet mysterious despite intensive studies since 1888 when Franz Hofmeister established the salt series. A combination of confocal Raman spectroscopy and contact angle measurements has enabled us to resolve the hydrogen bond relaxation (O:H―O, HB) and the associated charge polarization dynamics at different molecular site because of alkali halides hydration. Results show consistently that salt hydration softens the O:H phonon but stiffens H―O phonon cooperatively. The extent of HB relaxation and polarization is proportional to the electronegativity difference and ionic radius, following the order of Hofmeister series: X (R/η) = I (2.2/2.5) > Br (1.96/2.8) > Cl (1.81/3.0) > F (1.33/4.0) ≈ 0 for anions, and Y(R/η) = Na (0.98/0.9) > K (1.33/0.8) > Rb (1.49/0.8) > Cs (1.65/0.8) for cations. Observations suggest that ions create each an electric field that aligns, stretches, and polarizes water molecules, which relaxes the O:H―O bond cooperatively, depresses the molecular dynamics, and enhances the hydration shell viscosity and the skin stress. Exercises also demonstrate that Raman spectroscopy performs as a powerful tool for probing the molecular‐site‐resolved HB network relaxation dynamics in terms of phonon stiffness, molecular fluctuation dynamics, and phonon abundance transition under external stimulus. Copyright © 2016 John Wiley & Sons, Ltd.     

一种基于新型偏振干涉成像光谱仪的目标偏振信息探测新方法

提出了一种采用基于视场补偿型Savart偏光镜的新型偏振干涉成像光谱仪对二维目标偏振信息进行空间遥感探测的新原理和新方法.在新型偏振干涉成像光谱仪光学系统不变的情况下,通过旋转偏振干涉仪分别测出了三个不同角度下像面上各像点的光强值,反演出了二维面目标的斯托克斯矢量,并给出了各像点偏振度和偏振方向的理论表达式.采用计算机模拟实验对该探测原理和方法进行了验证,所得结果与理论完全符合.从理论和实践上扩展了干涉成像光谱仪的探测功能,与目前国内外所研究的成像光谱仪相比,该成像光谱仪既能同时探测目标二维空间信息和一维光谱信息,又提供了一种获得目标偏振信息的手段和方法.     

基于激光诱导偏振光谱与激光诱导荧光技术的CH4/AIR火焰参数测量

建立了激光诱导偏振光谱（LIPS）和激光诱导荧光（LIF）联合的燃烧流场诊断系统,测量了CH4/AIR预混火焰中心不同高度处的OH荧光光谱和激光诱导偏振光谱,计算了OH的浓度及燃烧场温度分布。分析了燃烧炉表面对荧光收集效率的影响,并对两种技术的测量数据进行了分析比对,获得了火焰中心OH密度的分布规律。实验结果表明,联合LIPS和LIF两种技术测量CH4/AIR预混火焰参数是可行的,两种技术测量结果的一致性较好,OH浓度的相对偏差小于5%,温度的相对偏差小于8%。     

多尺度水下偏振成像方法

水下偏振成像技术利用散射光偏振特性能够有效提高水下成像质量,在水下目标探测和识别领域具有重要应用价值.针对该技术在背景散射光和目标信息光分离时由于噪声放大现象导致重建图像质量受限的问题,提出多尺度水下偏振成像方法.该方法利用图像分层处理思想,结合小波变换的多尺度特性,对体现图像高对比度的基础层和低对比度但细节信息丰富的细节层分别进行处理,重建高对比度、高信噪比的清晰场景图像.实验结果表明,多尺度水下偏振成像方法不仅能够大幅提高对比度,复原图像细节信息,而且能够有效抑制放大噪声,提高重建图像的信噪比,在水下偏振成像领域具有良好应用前景.     

偏振遥感在伪装目标识别上的应用及对抗措施

为了研究偏振遥感对伪装目标的识别特点,分别对不同颜色的伪装网进行了偏振参数测量和成像实验。通过数据分析发现,伪装网的散射偏振度受观测条件和材料自身特性（如反射率、折射率和表面粗糙度）影响很大;伪装涂层对入射光的散射作用可以分为面散射和体散射,其中面散射具有起偏振作用而体散射具有消偏振作用;与自然背景相比,伪装目标的偏振特征非常显著,利用偏振遥感可以有效地识别出常规侦察手段所不能发现的伪装目标。通过偏振遥感的侦察原理和特点分析,提出了可以利用表面结构设计和烟雾等方法对抗偏振遥感的侦察。     

Electrochemical impedance spectroscopy and linear polarization applied to evaluation of porosity of phosphate conversion coatings on electrogalvanized steels

In this work, electrochemical impedance spectroscopy and linear polarization are used in determining porosity of zinc phosphates, and of nickel and manganese modified zinc phosphates on electrogalvanized steel. The porosity of the phosphate layers ranges from 0.1% for the manganese-modified hopeite to 8% for hopeite, using the linear polarization and the electrochemical impedance spectroscopy techniques. The porosity values measured using the two techniques were in agreement. All impedance spectra of coated samples showed two steps, with two capacitive arcs and an inductive looping.     

通道调制型偏振成像系统的偏振参量重建

通道调制型偏振成像系统中,焦平面上获取的信息需要通过目标偏振参量的重建才能有效提取,因而重建是目标识别、材料分析、生物医疗等技术进一步应用的前提.为了实现在非理想情况下通道调制型偏振成像系统的偏振参量精确重建,需要解决成像系统中电荷耦合器件(CCD)采样频率与频谱位置偏移对重建的影响.本文首先详细分析了频谱不发生混叠的条件:CCD采样频率应至少为4倍基频;在偏振干涉频谱位置偏移时,使用最大频谱法确定各个偏振态的载波频率,通过频移、滤波和傅里叶变换获得目标的偏振重建二维图像;最后通过计算机模拟仿真与实验分析结合的方法验证该重建方案的可行性与有效性.模拟与实验结果表明:改进后的偏振重建法得到的偏振图像与原始输入图像的均方差在0.001以下,峰值信噪比有明显的提高,且结构相似度可达到0.9以上,表明该方法获得的二维偏振态重建图像精度高,与理论偏振解调法相比具有很大的优越性.该工作希望为后续偏振探测与分析进一步的研究提供参考.     

利用偏振干涉成像光谱仪进行偏振检测的最佳角度分析

利用偏振干涉成像光谱仪进行偏振探测,这一方法将偏振测量与干涉成像光谱技术相结合,一方面能提供辐射测量所不能提供的物体偏振信息,另一方面又可获取目标的空间图像和光谱,具有比辐射测量更高的准确度.在简要分析了利用偏振干涉成像光谱仪进行偏振检测的理论基础上,深入研究了偏振检测的方法,分析比较了目前常用的偏振探测角度（45°,60°）对偏振度探测的影响.进一步计算推导出偏振测量的最优探测角度,将之与以往常用的探测角度进行了分析比较,证明了此最佳探测角度可以有效地减小偏振误差、提高偏振探测的精度.这将极大地提高偏振干涉成像光谱仪的应用范围,为新型偏振干涉成像光谱技术的研究以及仪器研制提供重要的理论依据. 关键词： 偏振检测 偏振干涉成像光谱仪 探测角 Savart偏光镜     

偏振遥感的侦察原理及应用

偏振遥感是一种新的遥感探测方法,它以目标辐射能量的偏振特征作为探测信息,能够很好的分辨目标上低反射区域和目标轮廓,在复杂的背景中提取目标的三维信息。介绍了偏振遥感的基本原理和国内外应用情况,分析了偏振遥感的特点和在识别人工目标方面的优势。