Establishment and Error Analysis of Model of Interference Fringe Contrast for Laser Tracing Measurement Optical System

A method was proposed to analyze the influences of the non-ideal spectroscopic performance of optical components and orientation errors of a laser tracing measurement optical system on the tracing measurement performance.A comprehensive model of the interference fringe contrast based on the laser tracing system s measurement principle was established in this study.Simulation results based on ZEMAX verified the model.According to the simulation results,the placement angle of the analyzer had a direct influence on the interference fringe contrast.When the angle of the polarized light to the analyzer’s transmission axis increased from 65°to 85°,each contrast of the four-way interference fringes decreased from 0.9996 to 0.3528,the interference fringe contrast is decreased by 65%.Under the split ratio of beam splitters in the interference part(BS 1)of 5∶5,when the splitting ratio of BS 2 changed from 2∶8 to 8∶2,the fringe contrast of the interference signals received by the photodetectors increased,but the injection light intensity onto the PSD reflected by BS 2 decreased.The significant influence of the tracing performance was verified by the experiments.When splitting ratio of BS 2 increased,the contrast of the interference fringes increased.Due to the weakening of the incident light intensity of the PSD caused by the change of BS 2 splitting ratio,the response time of the tracing system is increased by 23.7 ms.As a result,the tracing performance of the laser tracing measurement optical system was degraded.An important theoretical basis was provided to evaluate and improve the accuracy and reliability of laser tracing measurement systems.

Measurement of refrative index based on fiber Mach-Zehnder interference

In order to detect the refractive index of liquid with high precision,based on modular interference,Mach-Zehnder optical fiber refractive rate sensor was studied.Sensor structure is composed of ordinary single-mode fiber and multimode fiber,according to the singlemode multimode singlemode sequence to fuse together,and the fused optical fiber is used to process the taper.As a result,the diameter of the sensing head is about 10μm.Experimental results show that,as liquid refractive index increases range from 1.33 to 1.35,the loss peak of the transmission spectrum will shift to long wave direction.

Automatic abstraction of interference fringes with image technique

ion technique of interference fringes used in phase modulation and phase scanning modulation interferometer is presented. For the measurement of amplitudes of interference fringes, fringes are fitted and their central points are determined automatically according to their distribution rules. However, for the measurement of their phases, fringes should be recognized and processed with different calculating algorithms and least square optimization methods depending on the scanning modulation mode. When this technique is used for measurement of surface roughness, the measurement uncertainty is better than 5nm and the repeatability is less than 5%.

Two-Photon Interference Constructed by Two Hong–Ou–Mandel Effects in One Mach-Zehnder Interferometer

We present a two-photon interference experiment in a modified Mach-Zehnder （MZ） interferometer in which two Hong-Ou-Mandel effects occur in tandem and construct superposed two-photon states. The signal photons pass both the arms of the MZ interferometer while the idler photons pass one arm only. Interestingly, the probability of the idler photons emerging from any output port still shows a sine oscillation with the two-photon phase difference and it can be characterized only by the indistinguishability of the two-photon amplitudes. We also observe a two-photon interference pattern with a period being equal to the wavelength of the parametric photons instead of the two-photon photonie de Broglie wavelength due to the presence of two-photon phase difference, in particular, with complementary probabilities of finding the two-photon pairs in two output ports. The abundant observations can facilitate a more comprehensive understanding of the two-photon interference.

Fringe visibility and correlation in Mach–Zehnder interferometer with an asymmetric beam splitter

We study the wave–particle duality in a general Mach–Zehnder interferometer with an asymmetric beam splitter from the viewpoint of quantum information theory.The correlations(including the classical correlation and the quantum correlation)between the particle and the which-path detector are derived when they are in pure state or mixed state at the output of Mach–Zehnder interferometer.It is found that the fringe visibility and the correlations are effected by the asymmetric beam splitter and the input state of the particle.The complementary relations between the fringe visibility and the correlations are also presented.

基于CCD采集的Mach-Zehnder干涉条纹图的处理算法

Mach-Zehnder干涉仪适用于研究气体密度迅速变化的状态。由于气体折射率的变化与其密度的变化成正比,而折射率的变化将使通过气体的光线有不同的光程,因此可通过干涉臂变化对干涉条纹图像效果的影响得到气体密度。实测中,采用图像采集卡和CCD来接收Mach-Zehnder干涉仪产生的条纹图像,再通过计算机对条纹图像的条纹间距进行处理,从而得到气体密度的变化状态。从光干涉理论出发,对Mach-Zehnder干涉条纹图像特征进行了分析,建立了Mach-Zehnder干涉条纹的数学模型,并根据此模型设计了处理Mach-Zehnder干涉条纹图像的算法。算法包括图像的预处理(即图像的噪声提取)、图像的二值化及图像的细化。

对光纤Mach-Zehnder干涉仪的干涉场研究

研究了光纤Mach_Zehnder干涉仪的干涉场的特性 ,并对影响干涉效果的因素进行了分析 。

光纤Mach-Zehnder空间干涉系统的实验研究

深入细致地分析和研究光纤Mach-Zehnder空间干涉系统,详细介绍了各组成部分及功能,并对空间干涉场进行了理论分析,得到了线偏振光输出下的干涉场理论表达式和干涉场图.

Analysis of the Interference Signal of the Distributed Optical Fiber Sensing Based on DSP

In this paper, the author analyzes characteristics and extracting method of interference signal of the distributed optical fiber sensing. In the distributed optical fiber sensing, realizing alarm and positioning function only through the cross-correlation operation will increase the load of the system, can make misinformation rate of the system be improved greatly. Therefore, before the localization algorithm, adding a interference signal feature recognition is very necessary, can reduce unnecessary operation loss and reduce the load of the system, also reducing the number of the false positives.

The Formation of Fringes of Equal Chromatic Order across Double Clad Fiber in the Presence of High Power Lasers

Multiple-beam fringes of equal chromatic order interferometry is a powerful technique to extract optical properties over a continuous range of spectrum. In this paper we develop a theory for the spectral shape of the fringes of equal chromatic order (FECO) that are formed across a double-clad fiber. The modified single term Sellmeier dispersion formula is used to construct the refractive index dispersion curves for the liquid, claddings, and core. Expressions for the paraxial optical path length for several rays passing through the fiber and the liquid are developed. The condition of bright fringe is applied to get an analytical expression for the spectral shape of the FECO across a double-clad fiber with an elliptical/circular inner cladding. A potential application of this theory is to determine the dispersion of Kerr constant of the claddings and the core of the fiber. To illustrate the theory and its application, simulation examples are provided and discussed.

Measurement of Shear Stress Acting on Flat Plate Using Oil Film Interferometry

Measurements of frictional resistance play an important role in engineering practice. There are several types of air resistance acting on an aircraft, for example. One of them, frictional resistance, accounts for half of the air resistance. Oil film interferometry is one of methods for measuring the frictional resistance. Oil dropped on an object is thinly stretched by the frictional resistance. The bright and dark fringe pattern is generated when monochromatic light is applied to the oil film. The gradient of the oil thickness decreases with the lapse of time, and thus the spacing between neighboring the dark lines increases. The rate at which the spacing increases is proportional to the frictional resistance. In this study, the frictional resistance acting on a small area on a plate was measured and compared with the theoretical value. As a result, these results qualitatively agree well with each other.

柔性浅埋物的声-振智能探测

提出一种基于目标检测算法的柔性浅埋物的声-振智能探测方法,将声波激励、激光散斑干涉测振和目标检测算法有机结合,用以柔性浅埋物的大范围快速探测。在论述YOLO系列目标检测算法原理的基础上,选择并优化柔性浅埋物的智能探测网络模型;然后,搭建声-光融合智能探测系统,构建不同柔性浅埋物的激光散斑干涉条纹图数据集;最后,对数据集进行训练和测试,验证该算法用于干涉条纹图识别的可行性。实验结果表明:在给定实验条件下,柔性浅埋物智能探测网络模型的精确率为98.39%,召回率为84.72%,平均识别精度为99.66%。该声-振智能探测方法可以在给定实验环境下对多种柔性浅埋物的激光散斑干涉条纹图进行智能识别,适用于浅层地下柔性掩埋物的大面积快速探测。

基于深度学习的弱反馈自混合干涉信号滤波方法

采集激光自混合干涉信号的过程中会受到环境和电路噪声的干扰,导致信号失真。为了去掉噪声,最大限度保留原信号特征,提出了基于深度学习的自混合干涉滤波方法,该方法适用于弱反馈条件。使用自编码器作为神经网络,用加入噪声的信号作为输入,未加噪声的信号作为输出来训练网络。仿真结果表明:该方法处理含噪声自混合干涉信号时不仅能提高含噪声信号的信噪比,还能很好地保留干涉条纹的波形特征,即条纹的倾斜方向。实验中,使用深度学习方法滤波,再用条纹计数法进行位移重构,结果表明该方法对弱反馈条件下的自混合干涉信号有较好的滤波效果。

基于空洞空间卷积网络的点衍射干涉图像相位解包技术

为满足点衍射干涉测量对解包算法高精度、高效以及抗干扰的检测需求。提出一种基于空洞空间卷积的相移点衍射干涉图像的相位解包方法,通过将自编码器结构和空洞空间卷积结合获得更高的相位解包精度,实现对包裹相位图像可控的多尺度特征提取。根据点衍射图像特点制作的大量多样化数据集对其进行训练和优化,从而实现准确识别包裹相位所在阶次,最终可以快速处理包裹图像得到高精度的解包结果。利用所提方法对实际点衍射干涉图像进行处理,并与ESDI专业干涉图像处理软件以及其他解包算法处理结果进行比对,结果表明:本文解包结果与软件枝切法解包处理结果均方根误差值为0.0222 rad,面形拟合结果与软件面形拟合结果峰谷差值仅为0.0121λ、均方根差值仅为0.0042λ;时间效率上,完成一幅图像的处理平均仅需0.035 s,而传统方法均大于1 s。与其他方法相比,所提方法在处理包裹相位方面具有快速、高精度的特性,为点衍射干涉图像处理的高精度相位解包提供了新的可行方案。

薄膜干涉的衬比度研究

在薄膜干涉的相关教学中,教师和学生的关注点一般在于产生干涉的位置以及干涉条纹的分布状况,对干涉条纹的衬比度往往讨论的较少,而干涉场的衬比度对基于干涉的测量与制造是非常重要的.以菲涅尔反射公式为基础,从薄膜与背景材料的折射率差和光在薄膜上的入射角两方面,研究了薄膜干涉的衬比度,得到了一些具有价值的结论,这些结论对于学生进一步理解薄膜干涉,以及基于干涉的精密测量和微结构制造,具有一定的参考价值.

长波红外差分干涉仪光栅低温安装结构设计与优化

长波红外差分干涉仪在低温工况下会因光学元件受到非均匀应力作用产生干涉条纹的畸变,从而降低干涉仪系统性能。本文为解决低温工况干涉条纹弯曲畸变问题,基于长波红外差分干涉仪光机系统进行了干涉条纹畸变影响因素分析,结合光-机-热耦合分析方法,对干涉仪系统低温工作状态进行仿真。随后设计了针对影响条纹畸变的关键元件——光栅元件的低温微应力动态稳定支撑安装结构,结构优化后的光栅表面面形均方根(Root Mean Square,RMS)值为3.89×10^(-2) nm,面形峰谷值(Peak to Valley,PV)值为2.21×10^(-1) nm,分别较优化前初始系统的分析结果减小了5个数量级,系统仿真干涉条纹畸变小于1个探测器像元。全系统低温验证试验表明,优化结构可有效抑制干涉条纹畸变,畸变量小于2个探测器像元,试验与仿真计算结果一致性较好,验证了优化分析方法的有效性。该优化方案对提升反射式光学系统结构低温稳定性,提高系统工作能力有较大意义和价值。

改进PConvUNet图像修补的解包裹方法

包裹相位图是描述相位信息分布的二维或三维图像,广泛应用于光学干涉和计算机视觉等领域。精密齿轮齿面由于自身形状特征、加工及使用等因素影响,在激光干涉测量中包裹相位图常出现区域分布异常的条纹,导致解包裹时出现错误,极大降低了齿面形貌的测量精度。针对此问题,提出一种包裹相位图修补的解包裹方法,在PConvUNet网络中添加了深度残差模块与CBAM注意力模块用于修补相位图中质量差的包裹相位区域。实验证明,修补后的相位图能在解包裹时有效消除相位跳变点,有效提高了干涉图像处理的精度。

白光和激光扩展光源协同调节白光等厚干涉条纹

白光等厚干涉条纹是迈克尔逊干涉仪等光程的标志,由于其可观察范围小导致调节困难。通过分析常规调节方法中存在动镜调节方向、速度和是否消除回程差不易确定以及实验者易失去耐心等问题,提出使用白光和激光扩展光源协同调节的方法。根据激光干涉条纹的形状和移动方向确定动镜调节的方向和速度以及回程差是否消除,使实验者集中注意力,获得良好效果。通过实时对比激光和白光等厚干涉条纹,加深学生对白光等厚干涉条纹特点的理解。

原子团温度对原子干涉陀螺条纹对比度的影响

原子干涉陀螺是基于冷原子物质波Sagnac效应测量相对于惯性参考系的转动角速度的一种陀螺仪,其转动时会在2条干涉传播路径之间额外产生相移,该转动相移中包含了垂直于拉曼光方向的纵向速度分量。一般认为入射原子团的纵向速度分布是导致原子陀螺干涉信号强度减弱和条纹对比度下降的最主要因素,但这忽略了与拉曼光方向平行的横向速度分布的影响。通过建立原子干涉陀螺的简单数学模型,定量分析2种分布对相同转速的影响程度,发现横向速度分布对最终干涉条纹质量非常关键,其比纵向速度分布容忍度更低。这要求在设计原子干涉陀螺系统时,需要更重视原子团的横向冷却效率,而不是只关注和转动相移相关的纵向速度分布部分。

Comparative research and its significance of deformation measurements by technologies of laser real-time holographic interferome-try and radar differential interferometry

The principles and applications of laser real-time holographic interferometry （LRTHI） and radar differential interferometry （RDI） technologies are described in this paper, respectively. By using LRTHI, we can observe the deformation of samples under pressure in the lab and study the anomaly characteristics relating to different strain fields in different fracture-developing areas; while by using RDI, we can observe the landform and surface deformation. The results of deformation observed before and after the Ms=7.9 Mani earthquake （Tibet） and Ms=6.2 Shangyi-Zhangbei earthquake in China are obtained. It is pointed out that LRTHI and RDi are similar, which study the characteristics of anomalous deformation field by fringe variations for both of them. Therefore, the observation of deformation field in the seismogenic process, especially in the period impending an earthquake by RDI, and the comparative study in the lab by LRTHI are of great significance.