利用傅里叶分析法测量光相位延迟器延迟量

为了精确测量光相位器的延迟量,提出了一种新的测量方法,并利用米勒矩阵理论分析了影响测量结果的因素。测量系统主要由起偏棱镜、标准四分之一波片、检偏棱镜、锁相放大器和微处理器构成。该方法利用最小二乘算法得到了最优傅里叶系数,利用锁相放大器的窄带滤波作用提高了信噪比,利用反馈环控制系统对步进电机的步进角进行了控制。误差分析表明这一方法的绝对误差小于0.29°,对四分之一石英波片相位延迟量进行了实验测试,结果表明其重复测量误差小于0.40°。     

基于单光弹调制器的米勒矩阵测量技术

针对已有米勒矩阵测量方法的不足,提出了一种基于单光弹调制器的米勒矩阵测量技术,给出了米勒矩阵测量优化算法及系统参数两步校准法。该技术通过两步校准法对系统参数进行校准测量,利用优化算法计算得到待测样品的米勒矩阵。实验结果表明,待测1/4波片相位延迟量测量值为90.4185°,误差在标称偏差λ/300以内,快轴方位角测量值为0.2348°,误差在最大旋转误差0.4°以内。同快轴方位角为0°的1/4波片标准米勒矩阵相比,待测1/4波片米勒矩阵各元素最大相对误差的直接测量值和间接测量值分别为1.97%和0.83%,均小于最大相对误差的模拟仿真值2.11%。通过提高旋转台的读数精度和减小相位延迟量的标称偏差,可以进一步减小米勒矩阵各元素的最大相对误差。     

精确标定光弹调制器的新方法

针对现有光弹调制器标定方法的不足,提出了一种精确标定光弹调制器的新方法。首先利用起偏器、波片、光弹调制器和检偏器构成标定光路,通过寻找探测信号基频分量的极大值进行粗略标定,使光弹调制器的峰值延迟量处在1.841rad附近。然后撤走波片形成光弹调制器的精确标定光路,在检偏器旋转90°前后获得探测信号的直流分量和二次谐波分量。最后利用这两种探测信号的直流分量和二次谐波分量精确地计算出光弹调制器的峰值延迟量。实验验证了此光弹调制器标定方法,实验结果表明其标定误差仅为0.7%。在此光弹调制器标定方法中,光弹调制器的标定精度和入射光强、电路参量无关。同时,标定要求的峰值延迟量小,非常适合于光弹调制器在其使用波长范围长波段的标定。     

偏光干涉法测量波片相位延迟量和厚度

基于偏光干涉理论,提出一种宽光谱范围内测量波片相位延迟量和厚度的方法。利用矩阵光学方法分析了光谱透射率曲线与中值透射率直线交点波长之间的关系,给出待测波片的相位延迟量、波片厚度等多个物理量的计算公式并进行了误差分析。误差分析表明本方法相位延迟量测量最大误差为3.38°,厚度测量最大误差为0.66μm。实验上利用分光光度计验证了本方法的有效性。本方法能够实现波片多物理量的同时测量,且调节过程对于起偏器、检偏器透光轴方向及待测波片快轴方向无严苛要求,测量过程对波片也无损伤和污染,在波片加工、使用前质量评估等方面都具有一定的应用价值。     

基于双光束检偏的波片测量系统

大口径太阳望远镜中常用波片来进行偏振定标和偏振测量,为了对这类波片的延迟量和方位角进行准确测量,提出一种基于双光束检偏的波片测量系统,建立了该系统对应的数学模型。测量系统中检偏器的方位角可作为参数进行拟合,克服了单光束测量系统中检偏器方位角误差的影响;同时,根据测量系统的结构,对待测波片的延迟量范围进行分析,实现了对偏振定标和偏振测量中所使用波片的精确测量。分析了测量系统误差的主要来源,包括光源光强噪声、电机定位误差和探测器非线性响应,并对探测器非线性响应进行了校正。该方法测量1/4波片和127°波片的延迟量和方位角误差小于0.02°,测量27°～145°和215°～333°范围波片样品的延迟量和方位角误差小于0.05°。     

基于双弹光差频调制的中红外波片相位延迟高精度测量

提出了一种基于双弹光差频调制的中红外相位延迟精确测量方法。通过两个硒化锌型弹光调制器(PEM)的差频降低系统调制频率,产生载有被测相位延迟的低频调制信号,调制后的1倍差频幅值和2倍差频幅值相除可求得被测波片的相位延迟。该方法可有效抑制光强波动及PEM相位延迟波动对测量的影响,提高测量精度。对测量原理进行了理论推导,设计了硒化锌型PEM和实验系统。实验结果表明,相位延迟测量误差不大于0.004%,灵敏度可达5×10~(-4) rad。     

椭偏法测量云母波片相位延迟量及双折射率(英文)

为了得到云母波片的相位延迟量和双折射率随波长的变化关系,利用椭偏光谱仪连续测量了云母波片在400～770nm光谱范围内的延迟量.在对云母波片进行校准后,测量的数据被光电探测器收集并输送到计算机,根据输出的数据可以得到云母波片的相位延迟量随波长的变化.利用测得的延迟量计算出了云母波片在一定光谱范围内的双折射率,得到了云母波片的双折射率色散曲线,并通过拟合得到了双折射率色散公式.该方法能测量任意波片的相位延迟量,并且具有测量方便、周期短、精度高等特点.     

椭偏法测量云母波片相位延迟量及双折射率

为了得到云母波片的相位延迟量和双折射率随波长的变化关系,利用椭偏光谱仪连续测量了云母波片在400~770 nm光谱范围内的延迟量.在对云母波片进行校准后,测量的数据被光电探测器收集并输送到计算机,根据输出的数据可以得到云母波片的相位延迟量随波长的变化.利用测得的延迟量计算出了云母波片在一定光谱范围内的双折射率,得到了云母波片的双折射率色散曲线,并通过拟合得到了双折射率色散公式.该方法能测量任意波片的相位延迟量,并且具有测量方便、周期短、精度高等特点.     

基于弹光调制的双折射测试系统数据处理研究

干涉法和补偿法等双折射测量方法需要转动待测样品或偏振元件,操作不便、测量速度慢、精度有限。提出了一种双弹光调制与上位机组成的双折射系统。由弹光调制来产生调制信号,加载待测样品信息,调制信号采集至上位机中进行数据处理,进一步完成延迟量和快轴方位角求解。对测试方案原理进行分析,重点进行了系统数据处理的上位机设计与实现,完成了软硬件系统搭建。采用1/4波片进行了实验测试,实验结果表明延迟量测量相对误差为2%,快轴方位角测量相对误差为0.4%,延迟量和快轴方位角的标准差分别为0.056nm和0.022°。     

基于共线外差干涉的波片相位延迟的测量系统

通过共线光外差系统对光波所携带相位信息的精密检测,以及对波片光轴在入射面内的不同方位时寻常光(即o光)和非常光(即e光)的传播特性的理解,搭建了共线光外差测量系统对波片的相位延迟进行测量.实验结果表明该测量方法的测量精度达到±0.5°,并通过对光线斜入射时波片相位延迟的检测对该方法进行了验证.     

Limitation of carrier fringe methods in digital photoelasticity

The carrier fringes method has been proposed in digital photoelasticity in combination with techniques such as Fourier transform and phase shifting method, without considering the influence of the isoclinics on the isochromatic patterns analysis. Unlike other optical methods as moiré and holographic interferometry, in photoelasticity the light intensity emerging from a circular polariscope is related to both the isochromatic retardation and the isoclinic parameter. As it is shown by the theoretical analysis, owing to the misalignment between the principal stresses in the model and in the carrier, the computed retardation is affected by an error which is the same for all photoelastic methods based on the use of carrier fringes. Consequently, the photoelastic analysis carried out by methods that use carrier fringes cannot be applied as a full-field technique. In detail, numerical simulations show that the retardation error is comparable (less than 0.05 fringe orders) with that of other photoelastic methods provided that the misalignment between the principal stresses in the model and in the carrier is less than 30°. On the contrary, in the model zones where the misalignment is higher than 30°, the retardation measurement can be affected by non negligible errors (up to 0.25 fringe orders).     

1/4波片相位延迟分布的动态测量

通过密勒矩阵和斯托克斯参量法对一种1/4波片的相位延迟分布的测量模型进行了推导,并设计出一种空间分光移相器,取代一般测量系统中的检偏器,使得系统能于瞬间同时采集四幅具有90°移相步长的干涉图,避免了环境振动对测量的影响,从而可以对1/4波片的相位延迟分布进行动态在线测量.对一个实际标称波长632.8 nm的1/4波片进行了测量,结果显示其平均延迟量为149.36 nm,且接近75%部分其相位延迟误差在5 nm之内,显示出较好的延迟均匀性.     

四区域法消除偏振棱镜缺陷对波片相位延迟测量的影响

在起偏器-待测波片-检偏器系统基础卜提出一种四区域测量波片相位延迟量的方法.调整待测波片和检偏器的方位角,获得相应的四组光强值,通过线性运算得到待测波片的相位延迟量,完全消除了起偏器和检偏器不完全消光带来的误差.由于测量系统中不存在标准波片或其他相位调制元件,允许测量波长仅受偏振棱镜和探测器的限制,因此四区域法可适用于很大波长范围内的波片测量.以λ/4波片为例,理论分析了测量系统利用四区域测量法后的仪器误差为σφ≤士3.49065×10-3rad(约0.2°),精度比原算法提高约1个数量级.实验验证了四区域法能有效提高系统精度.     

Photoelastic stress pattern analysis using Fourier transform with carrier fringes: influence of quarter-wave plate error

The Fourier transform method, widely applied in photomechanics for the automated analysis of interferometric fringe patterns, has been recently extended to the photoelastic isochromatic fringe patterns analysis. Unfortunately, its use in photoelasticity involves some limitations that have not been completely highlighted in literature. This work deals with the influence of the quarter-wave plate tolerance on the evaluation of the retardation. Both theoretical and experimental analyses have shown that the quarter-wave plate error does not affect the retardation only if the principal stress directions in the model and in the carrier are aligned. In general, instead, the tolerance of the quarter-wave plates leads to an amplification of the retardation error due to the influence of the isoclinics with a subsequent restriction of the field in which the method can be applied. For instance, using common quarter-wave plates and tolerating a maximum retardation error of about 0.03 fringe order, than the Fourier transform method cannot be applied as a full-field technique but only in the model zones in which the misalignment between the principal stresses in the model and in the carrier is less than 15°.     

Phase retardation measurement by analyzing flipping points of polarization states in laser with an anisotropy feedback cavity

Phase retardation of wave plate is measured by analyzing flipping points of polarization states. Measured result and system error are analyzed. Nonlinearity of piezoelectric ceramic is an important error source. The nonlinearity is measured with an interferometer based on microchip Nd:YAG laser feedback phenomenon. The measured system of phase retardation, in this paper, is calibrated to the frequency splitting system. The accuracy of the system is improved. The measurement repeatability is better than 0.12° and the accuracy is better than 0.22°. This paper has a very important significance for wave plate high precision manufacture.     

The influence of the quarter wave plates in automated photoelasticity

During the last decades, several methods have been proposed to automate photoelastic analyses. Some procedures are based on the circularly polarised light by using quarter wave plates. However, quarter wave plates are typically matched for a specific wavelength, and an error is introduced at different wavelengths. The error of quarter wave plates affects the measurement of isochromatic and isoclinic data. In this paper, the influence of the errors of quarter wave plates in some of the most common automated photoelastic methods is reviewed. The errors in the photoelastic data are given and the procedures to reduce, or eliminate, them are also suggested.     

激光回馈波片位相延迟测量的误差源及消除方法

激光回馈法是一种新型的波片位相延迟测量方法。将波片放置在激光器与回馈镜之间,可使激光回馈波形产生偏振90°旋转（即跳变）现象,而两偏振态所占的周期比（占空比）与波片的位相延迟相关。通过测量占空比即可由计算机自动给出波片位相延迟。采用双向扫描回馈镜,2次获得并测出占空比,这样可以很好地消除两偏振态损耗的波动造成的测量误差,提高了该方法长期测量的稳定性。测量的重复性达到0.5°。该方法结构简单,在线测量精度高,满足工业化生产的需要。     

光学差拍方法测量波片的相位延迟

本文提出了用双频激光器测量波片的相位延迟方法:光学差拍方法,其测量精度为激光波长的1/6000,优于其他的波片测量方法的测量精度。