Large in-plane displacement measurement in dual-beam speckle interferometry using temporal phase measurement

Abstract

Measurement of in-plane displacements of a diffuse object by observing the temporal fluctuation of the speckle pattern in a dual-beam illumination speckle interferometer is illustrated. To conceive the temporal changes the object is displaced in its plane continuously. A high-speed camera is used to acquire a number of frames of the image of the object motion sequentially. Through Fourier transformation and inverse Fourier transformation of the frames stacked together, the total phase is determined. Finally, the magnitude of the in-plane displacement of the object motion is extracted. The range of displacement that can be measured using this novel method lies between few microns and over 100 μm on the upper end. Theory together with experimental results are presented in this paper.     

反射式强度型光纤传感器在微小位移精密测量中的应用

简要介绍反射式强度型光纤传感器的工作原理及各组成部分的作用。选择合适的光源、光纤对、检测器，对反射率不同的被测物进行位移测量，通过分析数据可以得到相应的位移测量参数；并分析了发送光纤与接收光纤轴间距对输出的影响。在实际测量中，可参照分析结果，根据被测物的情况选取合适的测量点。     

Simultaneous measurement of in-plane and out-of-plane displacement derivatives using dual-wavelength digital holographic interferometry

The paper introduces a method for simultaneously measuring the in-plane and out-of-plane displacement derivatives of a deformed object in digital holographic interferometry. In the proposed method, lasers of different wavelengths are used to simultaneously illuminate the object along various directions such that a unique wavelength is used for a given direction. The holograms formed by multiple reference-object beam pairs of different wavelengths are recorded by a 3-color CCD camera with red, green, and blue channels. Each channel stores the hologram related to the corresponding wavelength and hence for the specific direction. The complex reconstructed interference field is obtained for each wavelength by numerical reconstruction and digital processing of the recorded holograms before and after deformation. Subsequently, the phase derivative is estimated for a given wavelength using two-dimensional pseudo Wigner-Ville distribution and the in-plane and out-of-plane components are obtained from the estimated phase derivatives using the sensitivity vectors of the optical configuration.     

Fiber Bragg grating displacement sensor for movement measurement of tendons and ligaments

Biomechanical studies often involve measurements of the strains developed in tendons or ligaments in posture or locomotion. Fiber-optic sensors present an attractive option for the measurement of strains in tendons and ligaments because of their low cost, ease of implementation, and increased accuracy compared with other implantable transducers. A new displacement sensor based on a fiber Bragg grating and shape memory alloy technology is proposed for the monitoring of tendon and ligament strains in different postures and in locomotion. After sensor calibration in the laboratory, a comparison of the fiber sensors and traditional camera displacement sensors was carried out to evaluate the performance of the fiber sensor during the application of tension to the Achilles tendon. Additional experiments were performed in cadaver knees to assess the suitability of these fiber sensors to measure ligament deformation in a variety of simulated postures. The results demonstrate that the proposed fiber Bragg grating sensor is a highly accurate, easily implantable, and minimally invasive method of measuring tendon and ligament displacement.     

New set-up for in-plane permeability measurement

The determination of accurate permeability values is critical to process simulations for Resin Transfer Molding (RTM). New instrumentation is presented in this paper for high throughput permeability measurements. The design extends the original work of Hoes [Hoes K. Development of a new sensor-based set-up for experimental permeability identification of fibrous media, PhD thesis, Vrije Universiteit Brussels, Brussels, 2003] with a new sensor design, a much larger sensor pattern, and new analysis software. For example, the new analysis software is more robust than previous versions in that it will compute the flow front orientation angle rather than assume the angle as given by the user. The new set-up was used to measure the permeability of a basalt woven 3/1 twill fabric. When compared with previous work on 2/2 twill and plain woven fabrics, a relationship was observed between the breadth of the anisotropy distribution, the correlation between the principle components of the permeability tensor, and the fabric structure. Such a relationship has implications for manufacturing reliability, and may help explain why some fabrics process much more consistently than others.     

Optical in-plane strain field sensor

A whole-field speckle strain sensor is presented. The speckle strain sensor allows the measurement of all three in-plane components of the strain field simultaneously without touching the surface of the sample. The strain fields are extracted from the in-plane motion of defocused laser speckles in a telecentric imaging system. To distinguish the contribution to the speckle motion from surface translation, rotation, and strain, the speckle motion from three lasers with different illumination directions and wavelengths has to be analyzed separately. Simultaneous acquisition of the three individual speckle patterns is achieved by means of splitting the light from the lasers onto separate but synchronized detectors with the aid of dichroic mirrors. The motion of the speckles is calculated with digital speckle photography (speckle correlation), which enables the strain sensor to measure strain fields with noise levels as low as 10 microstrain.     

基于激光位移传感器的手持式轮对尺寸测量仪设计

针对轨道交通轮对几何尺寸检测需求不断增加、检测工具自动化水平低、检测精度低的现状,设计一种基于一维激光位移传感器的手持式轮对尺寸测量仪。该设备以STM32F407芯片作为微控制器,通过控制直线步进电机,配合激光位移传感器实现对轮对廓形二维点云数据的采集,采用基于中值误差与连续度调整权值的平滑算法对点云数据预处理,采用基于轮对轮廓特征的廓形匹配实现轮对尺寸参数的计算。该仪器对车轮轮廓进行全面记录和质量评估,试验证明,该设备在保持较高测量精度的情况下,同时具有高效测量、长时间工作等特点。     

Multidimensional CMOS in-plane stress sensor

This paper reports a novel multidimensional complementary metal-oxide semiconductor (CMOS) based stress sensor. The device uses an octagonal n-well in a p-substrate and eight peripheral contacts enabling the current to be switched in eight directions rotated by an angle of /spl pi//4. By taking full advantage of the piezoresistive behavior of single-crystal silicon, the measurement of all in-plane stress tensor components, i.e., /spl sigma//sub xx/, /spl sigma//sub yy/, and /spl sigma//sub xy/, is demonstrated. This information is derived from the zeroth and second angular-order Fourier components of voltage signals parallel and perpendicular to the switched current. Nonlinearities of the system are reduced by proper bias conditions using a center contact. The device was calibrated by applying defined normal stresses using a bending bridge setup. The device behavior was modeled including piezoresistive effects and the junction field effect by a combination of the finite element method and a nonlinear simulation program with integrated circuits emphasis (SPICE) network simulation using junction field effect transistor (JFET) elements. Stress sensitivities of 200 /spl mu/V V/sup -1/ MPa/sup -1/ are demonstrated for the determination of the three stress components.     

线位移传感器检定方法

本文详细描述了线位移传感器的外观、通电前的机械性能及迟滞、重复性、非线性等主要技术指标的检定步骤、检定原理和数据处理方法     

光纤Bragg光栅位移和温度双参量传感实验研究

采用一种新颖的等强度梁光纤光栅（FBG）传感结构,将光纤光栅沿梁轴向粘贴在传感梁上,并确保光栅的一半粘贴在梁上,另一半则沿梁的轴向呈自由状态,通过两部分光栅对梁自由端位移和环境温度的不同响应,实现温度和位移的同时测量,测量误差不大于4％。通过多次实验验证,所得结果与理论分析相符合。     

A displacement sensor for nonmetallic hydraulic cylinders

A sensor was developed to provide signals proportional to the position of the rod in a hydraulic cylinder. The sensor has a coil winding in the shell of the cylinder. The sensor operates by sensing the change in the coil impedance as the rod moves in the cylinder. This paper describes the construction of the cylinder and the sensor, and the performance evaluation of the sensor. Several different materials were placed in the rod and tested. For the cylinder tested, an aluminum core provided the highest precision, about 0.38 /spl Omega/. The full-scale output was 19.90 /spl Omega/ over a stroke length of 193 mm. The linearity was about 1.64% of full-scale. Shielding from electromagnetic interference can improve the precision dramatically. A ferrite-cored rod assembly yielded a much greater full-scale output, 1300 /spl Omega/, but exhibited significant hysteresis.     

Fiber-optic interferometric displacement sensor

Translated from Izmeritel'naya Tekhnika, No. 6, pp. 28–29, June, 1988.     

High-resolution electronic interferometry for the measurement of in-plane vibration

This study proposes an algorithm based on the standard deviation in the temporal domain to remove influences from background noise and ambient disturbance and enhance the quality of images obtained using interferometric technology. From measurements of the first ten in-plane resonant frequencies and mode shapes of vibrating zirconate titanate (PZT) laminates, we investigated the resonant characteristics in both the U and V directions. The resulting interference fringes were used to quantify the vibration amplitude of PZT plates on a submicron scale. The resonant frequencies obtained using the proposed method are in excellent agreement with those obtained using the finite element method and an impedance analyzer.     

Measurement of in-plane displacement by wavelength-modulated heterodyne speckle interferometry

The use of wavelength-modulated light incorporated into an optical-path-difference speckle interferometer is demonstrated as a heterodyne technique for measuring the in-plane displacement of a rough object. The in-plane displacement can be determined from the measured phase variation of the heterodyne speckle signal. We also improved the optical configuration to create a high-contrast interference pattern. Experimental results reveal that the proposed method can detect displacement up to a long range of 220 μm and displacement variation down to the nanometer range. Moreover, the sensitivity can reach up to 0.8°/nm. The performance of the system is discussed.     

Method for fringe enhancement in holographic interferometry for measurement of in-plane displacements

Theoretical background along with experimental results are given for a simple method for in-plane fringe enhancement in dual-beam illumination holographic interferometry. In this method, the fringes representing in-plane displacements arise as a moirépattern between two interferograms. To distinguish the in-plane displacement, a sequence of images is recorded while the reference mirror is continuously tilted at random. The in-plane fringes arethen found as the maximum contrast of the out-of-plane fringes in the image sequence. The resulting fringe quality is close to the quality of the out-of-plane fringes.     

Design and characterization of in-plane MEMS yaw rate sensor

In this paper, we present the design and characterization of a vibratory yaw rate MEMS sensor that uses in-plane motion for both actuation and sensing. The design criterion for the rate sensor is based on a high sensitivity and low bandwidth. The required sensitivity of the yawrate sensor is attained by using the inplane motion in which the dominant damping mechanism is the fluid loss due to slide film damping i.e. two–three orders of magnitude less than the squeeze-film damping in other rate sensors with out-of-plane motion. The low bandwidth is achieved by matching the drive and the sense mode frequencies. Based on these factors, the yaw rate sensor is designed and finally realized using surface micromachining. The inplane motion of the sensor is experimentally characterized to determine the sense and the drive mode frequencies, and corresponding damping ratios. It is found that the experimental results match well with the numerical and the analytical models with less than 5% error in frequencies measurements. The measured quality factor of the sensor is approximately 467, which is two orders of magnitude higher than that for a similar rate sensor with out-of-plane sense direction.     

Capacitive sensor for relative angle measurement

Based on a capacitive angle and angular rate sensor, a sensor measuring the relative angle between two rotating shafts has been developed. Two rotatable electrodes are placed between two sensor plates. The relative angle between the two rotors and the absolute position of the rotor blades are calculated from measurements of the capacitive coupling between different transmitting stator segments and a single receiving electrode. A prototype of this sensor has been developed with a range of the relative angle of /spl plusmn/7.5/spl deg/ with a resolution of 0.1/spl deg/.     

Optical configuration for TV holography measurement of in-plane and out-of-plane deformations

A novel TV holography method is proposed for parallel evaluation of in-plane and out-of-plane deformation fields. The method permits a trade-off between in-plane and out-of-plane measuring sensitivity. A four-exposure, four-frame phase shifting technique is used in the experiments; the experimental results for an aluminum specimen subjected to both rotation in its own plane and a bending couple load at the center are presented.