Optical Fiber Displacement Sensor with Ultra-high Resolution

A low fineness fiber optic Fabry-Perot interferometric displacement sensor has been developed and tested.A 0.005 nm displacement resolution is obtained by using He-Ne laser with a high performance ,photodetectors with low noise ,low drift operational amplifiers,6-pole Butterworth filters and perfect digital signal processing circuits.

NEW SELF-MIXING MICRO-INTERFEROMETER BASED ON EXTERNAL PHASE MODULATION

ASeblsf-tmraicxti：n gA innteewrf esreelnf-cme ioxcincgu rms iicnr oa -liansteerrf derioodmee t（eLrD b）a sbeyd r eofnl eecxtitnergn tahl ep lhiagshet fmroomdu ala tmioinrr oisr-plirkees etanrtgedet. in front of the laser. Sinusoidal phase modulation of the beam is obtained by an electro-optic crystal （EOC） in the external cavity. The phase of the interference signal is demodulated by Fourier analysis method. The combination of the modulation and demodulation decreases the sensitivity of the instru-ment to fluctuations of the laser power and the noise induced by environment. Experimentally, the new micro-interferometer is applied to measure the micro-displacement of a high precision commer-cial PZT with an accuracy of 〈10 nm.

Fiber Optic Displacement Sensor

A low finenesse Fabry-Perot interferometric displacement sensor has been developed and tested. With using a high stability He-Ne laser and perfect signal processing circuits, noise level of 0. 01nm equivalent to reflector displacement was obtained in a bandwidth of 0-1 kHz.

High-speed PGC demodulation model and method with subnanometer displacement resolution in a fiber-optic micro-probe laser interferometer

As the key of embedded displacement measurement,a fiber-optic micro-probe laser interferometer(FMI)is of great interest in developing high-end equipment as well as precision metrology.However,conventional phasegenerated carrier(PGC)approaches are for low-speed scenes and local error analysis,usually neglecting the global precision analysis and dynamic effect of system parameters under high-speed measurement,thus hindering their broad applications.We present a high-speed PGC demodulation model and method to achieve subnanometer displacement measurement precision in FMI.This model includes a global equivalent resolution analysis and revelation of the demodulation error mechanism.Utilizing this model,the failure issues regarding the PGC demodulation method under high speed and large range are addressed.Furthermore,an ultra-precision PGC demodulation algorithm based on the combination of static and dynamic delay adaptive regulation is proposed to enable high-speed and large-range displacement measurement.In this paper,the proposed model and algorithm are validated through simulation and experimental tests.The results demonstrate a displacement resolution of 0.1 nm with a standard deviation of less than 0.5 nm when measuring at a high velocity of 1.5 m/s—nearly a tenfold increase of the latest study.

Displacement measuring grating interferometer: a review

A grating interferometer, called the "optical encoder," is a commonly used tool for precise displacement measurements. In contrast to a laser interferometer, a grating interferometer is insensitive to the air refractive index and can be easily applied to multi-degree-of-freedom measurements, which has made it an extensively researched and widely used device. Classified based on the measuring principle and optical configuration, a grating interferometer experiences three distinct stages of development: homodyne, heterodyne, and spatially separated heterodyne. Compared with the former two, the spatially separated heterodyne grating interferometer could achieve a better resolution with a feature of eliminating periodic nonlinear errors. Meanwhile, numerous structures of grating interferometers with a high optical fold factor, a large measurement range, good usability, and multidegree-of-freedom measurements have been investigated. The development of incremental displacement measuring grating interferometers achieved in recent years is summarized in detail, and studies on error analysis of a grating interferometer are briefly introduced.

An Extrinsic Fiber Fabry-Perot Interferometer for Dynamic Displacement Measurement

A versatile fiber interferometer was proposed for high precision measurement. The sensor exploited a double-cavity within the unique sensing arm of an extrinsic-type fiber Fabry-Perot interferometer to produce the quadrature phase-shifted interference fringes. Interference signal processing was carried out using a modified zero-crossing （fringe） counting technique to demodulate two sets of fringes. The fiber interferometer has been successfully employed for dynamic displacement measurement under different displacement profiles over a range of 0.7 p.m to 140 p.m. A dedicated computer incorporating the demodulation algorithm was next used to interpret these detected data as well as plot the displacement information with a resolution of 2/64. A commercial displacement sensor was employed for comparison purposes with the experimental data obtained from the fiber interferometer as well as to gauge its performance, resulting in the maximum error of 2.8% over the entire displacement range studied.

Micro displacement reconstruction of self-mixing grating interferometer based on Littrow structure

An improved self-mixing grating interferometer based on the Littrow structure has been proposed in this Letter to measure displacement.The grating is integrated inside the interferometer to reduce the impact on the vibration parameters of the object caused by the grating attached to the vibrating object.The+1 st diffracted light returns to the laser cavity after being reflected by the target object,and self-mixing interference occurs.The displacement can be reconstructed by processing the self-mixing signals.The feasibility of the proposed interferometer is demonstrated by experimental measurements,and results show that it can achieve micro displacement measurement with the maximum absolute errors of less than 50 nm.

Reconstruction of Fabry–Perot cavity interferometer nanometer micro-displacement based on Hilbert transform

A novel reconstruction method of nanometer micro-displacement of Fabry-Perot(F-P)interference is proposed in this study.Hilbert transforms are performed for F-P interference fringes,and the obtained signal performs tangent operation with the original signal.Finally,the validity of the proposed algorithm and the structure are verified by simulation and several experimental measurements for vibration.Results from the experiments show that the maximum relative error is 4.9%.

Sinusoidal Phase-Modulating Fabry-Perot Interferometer for Angular Displacement Measurement

In this paper, a sinusoidal phase-modulating Fabry-Perot interferometer is proposed to measure angular displacement. The usefulness of the interferometer is demonstrated by simulations and experiments.

Long range dynamic displacement:precision PGC with sub-nanometer resolution in an LWSM interferometer

We propose a precision phase-generated-carrier(PGC) demodulation method with sub-nanometer resolution that avoids nonlinear errors in a laser wavelength sinusoidal modulation fiber-optic interferometer for long range dynamic displacement sensing.Using orthogonal detection and an AC-DC component extraction scheme,the PGC carrier phase delay(CPD) and laser intensity modulation phase delay can be obtained simultaneously to eliminate the nonlinear error from accompanied optical intensity modulation and CPD.Further,to realize long range displacement sensing,PGC phase modulation depth(PMD),determined by the laser wavelength modulation amplitude and the working distance of the interferometer,is required to maintain an optimal value during measurement,including initial position and dynamic movement.By combining frequency sweeping interference and modified PGC-arctan demodulation to measure real-time working distance,adaptive PMD technology is realized based on proportion control.We construct a fiber-optic Michelson and SIOS commercial interferometer for comparison and perform experiments to verify the feasibility of the proposed method.Experimental results demonstrate that an interferometer with sub-nanometer resolution and nanometer precision over a large range of 400 mm can be realized.

A modified moire interferometer for three-dimensional displacement measurement

This paper presents a new optical interferometric system, MMI-T/G, composed of a modified four-beam moire interferometer and a Twyman/Green interferometer. The MMI-T/G system can measure three-dimensional displacement fringe patterns with a single loading on the specimen, and the in-plane and out-of-plane displacement fields can be measured independently and defined clearly. The optical setup has the advantages of structural novelty, flexibility, and high fringe contrast. Moreover, the in-plane displacement sensitivity is twice of that of the normal moire interferometer. The measuring techniques to obtain the fringe patterns and displacement fields using the MMI-T/G system are described. The experimental results of thermal displacement of an electronic device are shown.

The technique of detecting the laser-ultrasonic vector displacement with a confocal Fabry-Perot interferometer waves in a plate

Generally, a confocal Fabry-Perot interferometer is only able to detect the out-of-plane component of a displacement field; while the in-plane component often has the information about the material which cannot be found in this out-of-plane component. In this paper, based on a confocal Fabry-Perot interferometer set-up for detecting the out-of-plane component of a laser generated acoustic field, a technique is developed to detect both the out-of-plane and in-plane displacement components simultaneously with a novel two-channel confocal Fabry-Perot interferometer.

Nanometer-scale displacement measurement based on an orthogonal dual Michelson interferometer

In this Letter,we propose a simple structure of an orthogonal type double Michelson interferometer.The orthogonal detection method overcomes the problems of uneven ranging sensitivity and the inability of traditional interferometers to determine the displacement direction.The displacement measurement principle and signal processing method of the orthogonal double interferometer are studied.Unlike the arctangent algorithm,the displacement analysis uses the arc cosine algorithm,avoiding any pole limit in the distance analysis process.The minimum step size of the final experimental displacement system is 5 nm,which exhibits good repeatability,and the average error is less than 0.12 nm.

Large-range displacement measurement using sinusoidal phase-modulating laser diode interferometer

A signal processing method of realizing a large-range displacement measurement in a sinusoidal phase- modulating laser diode interferometer is proposed. The method of obtaining the dynamic value of the effective sinusoidal phase-modulating depth is detailed, and the residual amplitude modulation is also taken into account. Numerical simulations and experiments are carried out to compare this method with the traditional one. We prove that, with this method, the sinusoidal phase-modulating laser diode interferometer can realize a centimeter-level displacement measurement range with high precision, which is much better than the traditional method.

基于矢量衍射理论的光栅干涉仪位移测量误差研究

光栅干涉仪位移测量系统作为测量领域中最精密的测量仪器之一,由于在测量过程中光栅的姿态位置无法保证完美装配,使得光栅的光栅矢量方向与运动矢量方向之间出现偏差,导致位移测量结果出现周期性非线性误差。文中针对在光栅干涉仪位移测量过程中出现的光栅与位移台以及读数头之间的姿态位置误差进行分析,通过分别建立位移坐标系及光栅坐标系,参考惯性导航领域中飞行器姿态表示方法,利用一维光栅的横滚、俯仰和偏航角共同描述一维光栅相对于位移台的装配状态。通过基于矢量衍射理论分析光栅干涉仪位移测量时三个维度的角度偏差量,对可能产生的位移测量误差进行了分析说明。基于广义一维光栅方程,探究出了一个更为普遍的结论,为后续装置的改进提供理论依据,以提高系统的测量精度。

星载迈克尔逊干涉仪直线动镜的柔性支撑结构研究

针对传统迈克尔逊干涉仪动镜支撑结构存在成本高、寿命低、维护难度大、大行程大负载下导向精度差的问题,设计了一种高精度迈克尔逊干涉仪角镜柔性支撑结构,具有低成本、高精度、大负荷的优点。提出以柔性支撑结构的承载能力、行程和导向精度为优化目标的结构刚度模型,选择材料和尺寸参数,开展运动结构设计。有限元分析结果表明该支撑结构在1.5 kg的负载(角镜)下,当行程达到4.5 mm时,柔性结构的最大拉应力约为169 MPa,结构安全裕量为1.98,角镜竖直方向的寄生位移小于4.1μm。专项测试结果显示,支撑结构承载1.5 kg负载(角镜)在4.5 mm行程内,竖直方向的寄生位移小于4.7μm,直线度的均方根误差为1.5μm,与设计结果较吻合,可以满足星载迈克尔逊干涉仪对高精度直线动镜的支撑要求。

Enhanced phase sensitivity of an SU（1,1） interferometer with displaced squeezed vacuum light

We study the phase sensitivity of an SU（1,1） interferometer with two input beams in the displaced squeezed vacuum state and the coherent state, respectively. We find that there exists an optimal squeezing fraction of the displaced squeezed vacuum state that optimizes the phase sensitivity. We also examine the effects of some factors, including the loss, mean photon number of the input beams and amplitude gain of the opl;ical parameter amplifiers, on the optimal squeezing fraction so that we can choose the optimal values to enhance the phase sensitivity.

超精密外差利特罗式光栅干涉仪位移测量系统

开展了扫描干涉光刻机工作台超精密位移测量的实验研究,以提高扫描干涉光刻机的环境鲁棒性。针对扫描干涉光刻机工作台位移测量精度,提出了新型高环境鲁棒性外差利特罗式光栅干涉仪测量系统。介绍了系统测量原理,设计了测量系统,提出了基于Elden公式的系统死程误差建模方法。设计制造了尺寸仅为48mm×48mm×18mm的光栅干涉仪。基于误差模型计算了死程误差,计算结果表明:对于1.52mm死程的光栅干涉仪,宽松的环境波动指标(温度波动为0.01℃、压力梯度为±7.5Pa、相对湿度波动为1.5%、CO2含量波动为±50×10-6)仅引起±0.05nm的死程误差。最后,设计了基于商用双频激光平面镜干涉仪的测量比对系统,开展了光栅干涉仪原理验证实验和测并量稳定性实验。原理验证实验表明:光栅干涉仪原理正确且系统分辨率达0.41nm。测量稳定性实验表明:常规实验室环境下,环境波动引起的死程误差为7.59nm(3σ)@<0.9Hz&1~10Hz,优于同等环境条件下平面镜干涉仪的31.11nm(3σ)@<0.9Hz&1~10Hz。实验结果显示系统具有很高的环境鲁棒性。

计量型原子力显微镜的位移测量系统(英文)

针对纳米结构表征和纳米制造的质量控制需要,中国计量科学研究院设计并搭建了一台计量型原子力显微镜用于纳米几何结构的测量。为了将位移精确溯源到国际单位米,研制了单频8倍程干涉仪测量位移,样品表面形貌则由接触式原子力显微镜测量。一个立方体反射镜与原子力显微镜的测头固定,作为干涉仪的参考镜。两个互相垂直的干涉仪用于测量样品与探针在x-y方向的相对位置。样品台置于具有三面反射镜的零膨胀玻璃块上,由压电陶瓷位移台驱动。另外两台干涉仪测量样品与探针在z方向的位移,探针针尖位于干涉仪光束的交点以减小Abbe误差。由于光学器件的缺陷产生的相位混合会引起非线性误差,采用谐波分离法拟合干涉信号来修正误差,修正后干涉仪测量误差减小为0.7nm。

用于位移精密测量的光外差马赫-泽德干涉仪

本文介绍了我们研制的用于位移精密测量的光外差马赫－泽德干涉仪。由于在光路设计中采用了共光路的布置，共模抑制技术得以实现，环境干扰产生的噪声得到很好的消除，相位检测的稳定性和精度大大提高。使用该干涉仪测量了一台在光学相移器内ＰＺＴ微位移驱动装置的电压－位移关系。测量结果具有良好的线性和重复性，与预期相符。根据测量数据分析，该光外差干涉仪具有３ｎｍ的位移测量精度。