白光光源光谱对白光干涉信号的影响

传统白光光源一般由一个纯高斯函数来进行模拟,通过改变中心波长和带宽来调节干涉信号.本文分别利用高斯模型和洛伦兹模型来讨论白光干涉信号,得出中心波长与相干长度的比值越大,零级条纹可见性越高,以及高斯模型的可靠范围.鉴于现代白光光源与传统光源不同,以发光二极管(LED)为例,模拟研究现代白光光源对白光干涉信号的影响.利用洛伦兹模型模拟白色LED光源时干涉信号存在凹陷,通过合理调整LED拟合光峰值间的距离降低凹陷对零级条纹的影响,以期得到在实际应用中干涉特性较优的白光光源光谱.     

低相干光源干涉系统在大口径拼接子镜间相位误差检测上的应用

针对大口径望远镜拼接式主镜,提出一种基于迈克耳孙干涉原理的低相干光源干涉检测系统.应用该系统对拼接子镜间相位失调误差进行实时检测.进而对失调子镜进行相应校正,以实现拼接子镜的共面排布.给出了低相干光源干涉检测系统的具体结构,叙述了干涉检测系统的检测原理,提出应用双中心波长组合低相干光源进行拼接子镜间相位误差检测,分析了系统最低信噪比.结果表明,双中心波长组合低相干光源系统,可以提高低相干光源下涉中心条纹的信号分辨能力.借以提高检测精度.使得低相干光源干涉测量系统对拼接子镜间的相位失调误差进行高精度提取.     

基于宽光谱干涉系统的拼接主镜共相位检测技术

 针对拼接式大口径望远镜主镜,提出一种基于迈克尔逊干涉原理基础上的宽带光谱（白光）干涉检测方法,对拼接子镜间相位误差进行实时检测,进而对失调子镜进行相应校正,以实现拼接子镜的共面排布。子镜间相位误差通过干涉图形间的不匹配性进行提取。应用双中心波长组合白光源来提高白光中心条纹的可见度,通过理论仿真,对不同中心波长组合的白光中心条纹可见度进行比较,结果表明：该双中心波长组合白光源系统的应用,可以提高白光干涉中心条纹的信号分辨能力,借以提高检测精度,使得该白光干涉检测系统对拼接子镜间的相位失调误差进行高精度提取。     

光源相干长度对光纤Fabry—Perot干涉的影响

从数值上分析了光源相干长度对光纤Fabry-Perot干涉的影响。推导了光源在理想情况和非理想情况下的光纤Fabry—Perot干涉模型,通过计算机模拟了干涉信号,指出在非单色光源下,干涉条纹失去周期性,随着腔长相干长度比增加干涉条纹的变化幅度减小,最后演化成一条直线,条纹的可见度也慢慢趋近于零。综合考虑了光纤的耦合效率和光源的非单色性对干涉信号的影响,随着腔长的增加,干涉信号的幅值和变化幅度都在减小,信噪比变差。要得到好的干涉信号,腔长不宜选择过大,必须使光源的腔长相干长度比值低于0．1。     

非单色性光源对杨氏干涉条纹可见度的影响

光源的单色性影响其相干性. 任何实际的波列都有一定的谱线宽度, 谱线宽度表示了光源单色性的好 坏, 直接影响了干涉条纹的可见度. 对非单色性光源通过典型杨氏双缝干涉装置产生干涉条纹的理论进行分析和 仿真, 得出谱线宽度与干涉条纹的可见度的关系. 结论与实验相吻合. 其结果对于干涉法工程测量具有现实意义     

单色扩展光源杨氏双缝干涉可见度的理论模拟

杨氏双缝干涉实验中, 在理想单色扩展光源照射下, 干涉条纹的可见度不仅仅和光源宽度有关. 本文 理论模拟了理想单色扩展光源照射情况下光源宽度、 狭缝间距离等多项因素对干涉图样可见度的影响, 模拟结果 有助于学生对单色扩展光源干涉图样清晰程度的理解和掌握     

改变写入Bragg波长的干涉条纹运动的扫描式Talbot干涉仪

一种干涉条纹运动的扫描式Talbot干涉仪被用于改变光纤Bragg光栅的写入Bragg波长。在系统中,光纤光栅是由来自相位掩模的±1级衍射光经平面镜反射后在远场形成紫外干涉条纹写入的,其中,相位掩模被用作±1级衍射光的分束器。值得注意的是通过干涉条纹的运动来扫描写入光纤光栅,有效降低了Talbot干涉仪对写入光源相干性的要求。     

独立伪热光源的双光子干涉

自Dirac提出一个光子只能与自己干涉之后，Mandel等人用两个独立的激光器实现一阶干涉实验，引发了人们对于独立光源干涉问题的更多关注和探讨。我们首次以两个独立的伪热光源观察到二阶关联亚波长干涉现象。在实验中发现当两个独立的光源偏振相同时，固定一个单光子探测器扫描另一个探测器，通过符合探测能够探测到类经典的一阶干涉；在反对称的方向（x，-x）同时扫描两个探测器，能够探测到亚波长干涉条纹。用经典的理论方法也可对此现象作简单的解释。当光源的偏振互相垂直时，则无法探测到类经典的一阶干涉或亚波长干涉。这些实验现象将有助于人们理解双光子干涉的本质；热光因其双光子特性有可能有些特殊的应用。     

迈克耳孙干涉仪测折射率时的异常现象研究

针对迈克耳孙干涉仪以激光为光源测量玻璃板折射率所产生的异常现象,本文从几何光学理论出发进行了讨论,简明直观地给出了干涉条纹吞吐转折点与零光程点、光程、虚光源相对位置之间的关系,并与实验数据进行了对比.     

新型干涉条纹计数器的设计与应用

针对用迈克尔逊干涉仪测量激光波长实验需要人工记录干涉环改变数量问题,研制一种干涉条纹自动计数器。该计数器不仅能显示干涉条纹改变数量,还能显示不同光强对应信号强度。同时,准确度高、操作简便,能在不同背景光强环境和光源光强条件下使用。     

Variable wavelength interferometry of birefringent retarders

A new interferometric procedure is proposed for testing birefringent retarders. The procedure uses monochromatic light with a continuously variable wavelength and two parallel pointer lines localized at a distance from each other in the fringe interference field of a double-refracting interferometer. The zero-order fringe of the empty interference field is brought into coincidence with one pointer line, and higher-order interference fringes displaced by an object under study are next brought into consecutive coincidence with the other pointer line as the wavelength of the monochromatic light is continuously varied.     

基于连续光谱光源的单色仪标定方法

单色仪在加工和安装过程中不可避免的存在误差,必须对其进行标定后才能使用。传统上采用汞灯的标定方法,波长数量有限,限制了单色仪的标定精度。在研究光栅单色仪原理的基础上,提出了一种基于连续光谱光源的单色仪标定方法,设计并搭建了标定实验系统,系统由宽波段光源、光源电源、滤光片、单色仪、光谱仪及计算机构成。采用卤钨灯作为光源,用光谱仪分别测量卤钨灯经单色仪后的辐射、直接测量卤钨灯的辐射,二者相比得到单色仪透过率函数,消除了卤钨灯辐射以及光谱仪响应函数的影响。在刻度盘的某一读数位置,获得单色仪透过率函数并进行归一化,并计算峰值波长,得到一组峰值波长和刻度盘读数的数据。该方法共采集了22组波长数据,用于单色仪的标定。分别采用8点、14点、18点、22点,采用线性拟合和二次拟合,得到了单色仪的波长与刻度盘读数的关系式。标定点数从8个(8点标定类似于汞灯特征谱标定)增加到22个,误差减小明显,将22点二次拟合的结果作为单色仪最终的标定结果。实验结果表明,采用连续光谱光源的单色仪标定方法获得的标定点数更多,标定结果优于传统的采用汞灯的标定方法。     

Determining large step heights using zero-order interference fringe identification and an external cavity diode laser

Zero-order interference fringe identification is a powerful tool for measuring large step heights. In contrast to white light scanning interferometry, this study utilizes an external cavity diode laser as the light source. The zero-path difference point can be accurately identified by combining wavelength scanning interferometry, in which the laser wavelength is continuously changed, with single wavelength interferometry, in which the laser wavelength is fixed. The experimental apparatus is a two-arm interferometer containing the sample in the measurement arm. The step height denotes the distance between two locations of a zero-order interference fringe, which are obtained by continuously varying the length of the reference arm. The accuracy of a sample of 10 mm step height was found to be 0.33 μm.     

光声光谱技术在多组分气体浓度探测中的应用

CO和CH_4气体作为判断变压器运行状态的故障气体,对其浓度的探测在变压器维护中具有重要意义.为了准确探测变压器运行过程中产生的CH_4和CO气体浓度,本文利用光声光谱技术,设计了一套基于宽带光源的多组分气体探测系统,和共振型光声系统相比,该系统中所用的非共振型光声池体积小,易加工,池内各处信号强度相同,降低了对声学信号探测器的安装要求.系统的性能通过对CO和CH_4气体的探测进行评估.首先,从理论上分析了信号强度与调制频率呈反比,然后根据宽带光声系统在不同调制频率下的响应,确定系统的最佳调制频率为22 Hz.在最佳调制频率下,根据温度与待测气体光声信号的关系,对光声信号进行温度补偿,消除温度变化对光声信号的影响,进一步提高了系统的稳定性.最后,通过不同浓度的CH_4和CO气体对系统进行标定.实验表明,温度补偿前后,光声信号随温度的漂移分别为0.023 23V/℃和8.383 48×10~(-5) V/℃,通过对不同浓度CH_4和CO气体的探测,系统的线性度分别达到0.995和0.998 4.在一个大气压下,积分时间为1s时,宽带光声探测系统对CO和CH_4气体的探测极限浓度能够达到1μL/L.该系统成本低,线性度好,探测灵敏度符合国标对变压器维护过程中CO和CH_4气体的探测要求.     

The Effects of Motion on Dynamic Moiré Interferometry

Experimental techniques (e.g. laser interferometry, photoelasticity) that generate fringe data are currently being utilized for analyzing full-field surface deformations in a variety of dynamic problems in experimental mechanics. As opposed to static problems, the transience of surface deformations in dynamic problems poses a unique problem in accurately resolving the fringe data that is acquired. Neumann determined that for time-lapse, double-exposure holographic interferometry the fringe contrast depends on the data acquisition time, wavelength of the light source, and transience of the dynamic phenomena. Dally performed a similar analysis for dynamic photoelasticity, where the dependence was on the stress gradients instead of the wavelength of the light source. This paper attempts to extend the analysis of Neumann and Dally to the analysis of transient fringe intensity data obtained from using dynamic moiré interferometry. It is found that the fringe contrast can depend on the frequency of the fringe field rather than the wavelength of the light source or stress gradients, and the fringe contrast will decay more rapidly for Gaussian light sources than constant intensity light sources. © 1997 Elsevier Science Ltd. All rights reserved.     

Enhancement of the relative visibility of the central fringe in the output of a white light interferometric system with a synthetic source

A study of the enhancement of the relative visibility of the central fringe in the output of a white light interferometric system with a synthetic source has been carried out. A theoretical analysis and an experimental investigation of the relative intensities of the central fringe in the output has been given and a comparison with the system discussed in this paper. A conventional two wavelength system has also been included. The results show that the relative intensity of the central fringe of the multiplied output is independent of the intensity ratio of the two wavelength components.     

光纤中双宽带抽运SBS慢光及其脉冲展宽减小的理论研究

提出了一种单模光纤中采用双宽带抽运实现宽带受激布罩渊散射(SBS)慢光的方法.给出了双宽带抽运的SBS慢光及其脉冲展宽的理论模型.色散分析发现,两抽运光间存在一个最佳的频率间隔,可有效地减少由于群速度色散所引起的脉冲展宽.理论计算表明,该方案所获得的SBS增益带宽和信号脉冲群延迟分别提高到了相同条件下单宽带抽运的1.7倍和2倍.     

Achromatic stellar interferometry

One drawback of Michelson's stellar interferometer is due to the fact that the period of the interference fringes is proportional to the wavelength. Hence, in broadband light the fringe contrast is low, or in narrowband light (after filtering) the luminosity is low. We propose a modified stellar interferometer with perfectly achromatic fringes, that has better light efficiency and better signal to noise under most circumstances. To that end, two pieces of grating have to fill the two apertures of Michelson's setup. Achromatic interference fringes occur somewhere along the system axis, where the plus-first diffraction order from one aperture meets the minus-first diffraction order from the other aperture. Laboratory experiments confirm the predicted achromatic performance.