正弦相位调制型激光自混合干涉仪的实时位移测量技术

采用正弦相位调制技术与时域解调相位方法相结合,提高激光自混合干涉仪在大量程位移测量中实时测量的准确度和速度。通过在激光器外腔中放置的电光晶体调制器对光束进行正弦相位调制,采用时域解调相位方法解调干涉信号相位。同时满足了大量程位移测量过程中的速度要求以及实现干涉仪位移测量的实时性。实验上,用PI公司高分辨率的商用电动位移平台标定的结果验证了该正弦相位调制激光自混合干涉仪在百毫米级大尺度位移测量中可达到小于0.5μm的位移测量误差。对干涉仪在实时位移测量中的影响测量速度的因素进行了分析,得出了本干涉仪的测速上限。     

光热正弦相位调制干涉仪中相位的抗干扰测量

在正弦相位调制半导体激光干涉仪中,半导体激光波长随注入电流和温度漂移而产生相位测量误差,同时干涉仪的机械振动和干涉仪两臂中的空气扰动也会引入相位误差,在已有光热正弦相位调制干涉仪中引入反馈机制,有效地降低了上述误差,增强了干涉仪的抗干扰能力,使用此干涉仪测量了物体的位移,测量结果表明这种方法可以有效地提高相位的测量精度。     

自混合干涉信号的位相调制

自混合干涉因其结构简单、紧凑、稳定且易准直等特点而被广泛应用于测量领域。从自混合干涉和电光晶体调制位相的基本原理出发,通过将电光晶体引入自混合干涉外腔调制,研究了自混合干涉测量中电光晶体的位相调制性能。实验证明,利用晶体的调制性能对自混合干涉信号进行位相调制,在很宽的频率范围内都能保证很高的调制精度,测量误差小,具有很好的应用前景。     

基于频分复用技术的激光反馈干涉二维动态位移测量

提出了一种基于频分复用技术的激光反馈干涉二维动态位移测量方法。激光器输出的光被分为两路,分别以±1级自准直衍射角入射至反射光栅,并沿原光路返回至腔内产生激光反馈干涉效应。在±1级衍射光路中放置电光晶体对光束相位进行高频调制,利用频分复用技术实现二维动态位移的测量。实验结果表明,所提方法能够重构出物体的二维动态位移,位移分辨率可达10 nm量级。所提方案通过在激光反馈干涉仪中引入衍射光栅,提高了激光反馈干涉测量系统的稳定性和抗环境干扰能力,同时也为使用单光源进行多维度微位移测量提供了新的思路。     

基于频分复用技术的激光反馈干涉二维动态位移测量

提出了一种基于频分复用技术的激光反馈干涉二维动态位移测量方法。激光器输出的光被分为两路,分别以±1级自准直衍射角入射至反射光栅,并沿原光路返回至腔内产生激光反馈干涉效应。在±1级衍射光路中放置电光晶体对光束相位进行高频调制,利用频分复用技术实现二维动态位移的测量。实验结果表明,所提方法能够重构出物体的二维动态位移,位移分辨率可达10 nm量级。所提方案通过在激光反馈干涉仪中引入衍射光栅,提高了激光反馈干涉测量系统的稳定性和抗环境干扰能力,同时也为使用单光源进行多维度微位移测量提供了新的思路。     

正弦相位调制式全光纤微位移测试仪

利用正弦相位调制干涉技术检测微小位移,精度可达纳米量级。采用全光纤光路,结构简单,并可实时非接触测量。     

反射式电光调制非互易相位调制器设计

基于反射式电光相位调制原理与偏振器、法拉第旋光器结合,提出了一种用于光纤环形干涉仪的非互易相位调制方案。其结构利用铌酸锂晶体不同切向电光特性,构成环形干涉仪上顺逆两束可调相位干涉信号,特别是引入信号能量损耗较小的全反射棱镜,实现非互易相位调制,有效降低了相位调制器半波电压。实验测得反射(调制两次)结构相位调制半波电压比透射(调制一次)下降一半,并用于光纤环形干涉仪调试,获得检测信号与调制信号相位线性相关,为下一步原理样机的研制提供可行性参考。     

基于相位凝固技术的激光反馈干涉术

针对激光反馈干涉术,提出基于相位凝固技术的调制解调方法,用以提高位移测量的分辨率,并设计了利用相位调制器进行调制的位移测量系统.利用调制器进行外腔相位调制,采集调制相位相对固定的干涉光信号,通过解调重构得到被测的位移信息.进行了信号调制、采样、重构技术的研究以及误差分析,并通过仿真验证了方法的可行性.结果表明,采用5点相位凝固采样技术,测量准确度可以达到λ/20.此方法可提高激光反馈干涉术的测量分辨率,实现信号实时采集处理,可用于位移的实时测量.     

基于相位调制器与Fabry-Perot干涉仪的激光多普勒频移测量方法

提出了一种激光多普勒频移测量方法, 此方法利用正弦相位调制使信号光在原频率成分基础上产生正负一阶边带, 再由Fabry-Perot干涉仪对调制光振幅和相位进行调整, 使其产生固定频率的拍频信号, 利用此拍频信号的振幅随频率变化而变化的性质来进行多普勒频移测量. 通过理论分析证明该方法具有很高的测量精度, 加工装调难度不大, 兼顾了普通相干与非相干探测方法的优势. 另外通过实验证明该方法的正确性与可行性, 并通过与普通非相干方式比较发现该方法在测量精度上可以提高 约1个数量级. 关键词： 多普勒频移 相位调制 Fabry-Perot干涉仪 拍频     

电控径向双折射滤波器的横向超分辨与轴向扩展焦深

提出利用电控径向双折射光瞳滤波器实现横向超分辨性能参量的调制与轴向扩展焦深。该光瞳滤波器由两个平行偏光镜,一个电光晶体与一个径向对称双折射晶体组成。分析了电光晶体与径向双折射元件对光偏振态的空间调制作用,通过控制电光晶体的相位延迟实现径向中心处初始偏振态的控制,与径向双折射元件横向偏振态调制结合,实现了庞加莱球上偏振态演变路径与阶段的控制,从而对焦点附近偏振态进行空间调制以实现光强的重新分布。研究结果表明,外加电场调制可以实现横向上超分辨性能的调控以及轴向上焦深的扩展,并可得到相应的电光相位延迟范围。     

Self-mixing interferometer based on temporal-carrier phase-shifting technique for micro-displacement reconstruction

A novel self-mixing interferometer based on temporal-carrier phase-shifting technique is presented. The phase of the laser beam is modulated with a triangular wave by an electro-optic modulator (EOM) in the external cavity. Phase demodulation of the interference signal is achieved by five-step Schwider-Hariharan algorithm combined with a special sampling technique. Theoretical analysis and simulation results are presented. Some errors of the technique have been discussed. Experimentally, the new interferometer is applied to measure the displacement of a high precision commercial PZT and a displacement measurement accuracy of λ/60 can be obtained.     

Quadrature demodulation technique for self-mixing interferometry displacement sensor

A new, to the best of our knowledge, signal processing method based on quadrature demodulation technique is presented for laser diode self-mixing interferometry(LDSMI) displacement sensor. Phase modulation of the laser beam is obtained by an electro-optic modulator (EOM) in the external cavity. Detection of the target's displacement can be easily achieved by sampling the interference signal at those times which satisfied certain conditions. The major advantage of the technique is that it does not involve any complicated calculation and insensitive to the sampling error. Experimental results show that the proposed method can effectively improve the displacement measurement resolution of the laser diode self-mixing displacement sensor to a few nanometers.     

Self-mixing interferometry based on sinusoidal phase modulation and integrating-bucket method

In order to realize real-time displacement measurement with high resolution, sinusoidal phase modulation and integrating-bucket method are introduced in the self-mixing interference (SMI) system firstly. The phase of the laser beam is modulated by an electro-optic modulator (EOM) in the external cavity. Theoretical analysis, simulation results and error evaluation are presented. Experimentally, the micro-displacement of a high-precision commercial PZT is reconstructed and the reconstruction accuracy is on the order of nanometers for displacements of a few micrometers.     

Numerical simulation of phase modulation method used as high sensitive self-mixing vibrometry in vertical-cavity surface-emitting laser

The self-mixing interference technique is a compact sensing technique that has widely used for measuring vibrations. For purpose of increasing the accuracy of the vibration measurement system, a new phase modulation technique based on the self-mixing interferometer is presented. The phase modulation is obtained by varying the length of external cavity periodically. The vibration information of the external target is determined by the Fourier analysis method. Theoretical analysis and numerical simulations of phase modulation method used as high sensitive self-mixing vibrometry based on vertical-cavity surface-emitting laser are given in this paper.     

All-fiber self-mixing interferometer for displacement measurement based on the quadrature demodulation technique

The quadrature demodulation algorithm used for all-fiber self-mixing sensors is applied to displacement measurements. A fiber electro-optic modulator is used to introduce phase modulation, which can improve the accuracy of measurements. Although phase modulation is easily affected by the polarization state of light, this method can process signals by sampling the interference signals at specific time points. Such signals are insensitive to polarization, and thus, the calculation process and experimental devices are simplified. The feasibility of the algorithm is validated via a series of experiments under nonpolarization-maintaining conditions.     

Displacement measurement method based on laser self-mixing interference in the presence of speckle

In order to achieve the accurate measurement of displacement, this Letter presents a self-mixing interference displacement measurement method suitable for the speckle effect. Because of the speckle effect, the amplitude of the self-mixing interference signal fluctuates greatly, which will affect the measurement accuracy of displacement. The ensemble empirical mode decomposition is used to process the interference signal, which can filter out high-frequency noise and low-frequency noise at the same time. The envelope of the self-mixing interference signal is extracted by Hilbert transform, and it is used to realize the normalization of the signal. Through a series of signal processing, the influence of speckle can be effectively reduced, and the self-mixing interference signal can be transformed into standard form. The displacement can be reconstructed by fringe counting and the interpolation method. The experimental results show that the method is successfully applied to the displacement measurement in the presence of speckle, which verifies the effectiveness and feasibility of the method.     

一种利用电光效应测量微小转角的新方法

利用线性电光效应发展出一种新的、高准确度的微小转角测量法.根据W.L. She等人提出的线性电光效应耦合波理论，求得出射光强与入射光强比值（即出射率）对入射光方向的依赖曲线，利用该曲线，通过测量出射率可以确定入射光的方向.并根据此原理，设计了一套简单的装置，该装置可以测量出物体微小转角的变化量，同时测量范围及准确度都可通过外加电场和入射光波长加以调节.对此微小转角测量法作了理论分析，在LiNbO3器件上，得到测量范围大于3′，准确度为3.5″的设计结果.     

电光晶体补偿位相测量微小位移及其应用

介绍一种应用电光晶体补偿位相测量微小位移的方法,着重分析其测量精度,并应用这种方法校正压电陶瓷的线性,精度优于1%波长。     

Fourier transform method for self-mixing interference signal analysis

Self-mixing interferometry (SMI) has been used to measure the distance and displacement. Although the principle of self-mixing interference is different conventional interference, we concluded that FFT analysis technique could also be used to detect the signal phase and increase the measurement precision of self-mixing interferometry.First the SMI signal is obtained by feeding the light from the target to cavity of laser diode, then it is pre-processed by an analog subtraction circuit to remove the overlapped output intensity due to the injection current modulation. Finally, SMI signal is analyzed by FFT phase detection method. Theoretical analysis and simulation calculations are presented. Experimentally, displacement of a PZT-driven target was measured with a precision of λ/50.