A displacement-measuring instrument utilizing self-mixing interferometry

We develop a self-mixing laser interferometer for the measurement of displacements on a generic target surface. The measurement is based on the bright-speckle tracking, a technique we have recently proposed to solve amplitude fading associated with the speckle statistics when the displacement to be covered is well in excess of the speckle longitudinal size. We implement the dynamical tracking of speckle maxima with piezo actuators and a phase-sensing loop. Also, we use an automatic gain control, based on a liquid crystal attenuator, to improve the amplitude statistics. Details of digital signal acquisition with adaptive signal processing through a field programmable gate array are discussed. The resulting instrument offers sub-/spl mu/m resolution in the measurement of displacement up to 500 mm of total shift, has virtually no need for alignment, and has very relaxed target-surface requisites, yet works with a very simple and inexpensive set-up.     

Measurement of absolute displacement by a double-modulation technique based on a Michelson interferometer

A novel method is presented for of measuring absolute displacement with a synthesized wavelength interferometer. The optical phase of the interferometer is simultaneously modulated with a frequency-modulated laser diode and optical path-length difference. The error signal originating from the intensity modulation of the source is eliminated by a signal processing circuit. In addition, a lock-in technique is used to demodulate the envelope of the interferometric signal. The displacement signal is derived by the self-mixing technique.     

CCD图象传感器在桥梁动态位移测量系统中的应用

CCD (charge coupled device)图象传感器是近年来发展起来的新型固体图象传感器件,具有光电转换、信号存储和信号传输等功能,在图象传感、信息处理和信息存储等方面得到广泛的应用。本文介绍了 CCD 图象传感器的结构、原理、特点和用途,并具体介绍 CCD 在桥梁动态位移测试系统研制中的应用。该系统采用TCD142D 作为传感器件,由桥跨位移测量子系统、桥础位移测量子系统和数据处理子系统组成。在系统测试软件的支持下,可以测量桥梁动态位移的时域曲线,强迫振动的频谱和桥梁的自振频率,冲击系数,横向两测点间倾角和阻尼值。该系统成功地解决了军用桥梁二维、动态、大位移和多参数的远距离非接触测试问题。     

基于超声波A/D采样法的相位差位移测量方法

为了提高超声波位移测量分辨率,提出一种基于超声波A/D采样法的超声波相位差位移测量方法,利用超声波信号的相邻采样数据之差,消除了超声波信号中的直流成分对相位差位移测量的影响,再通过不同相邻采样数据之差的比值建立了相位差位移测量的数学模型,由此获得较高的相位差位移测量分辨率。该方法的采样电路简单,不需要高倍数超声波信号采样率,仅需在一个超声波信号周期里采样10几个数据,就可获得亚微米级的位移测量分辨率。实验结果验证了该方法的有效性。基于该方法研制的超声波位移测量平台,若超声波频率选用40 kHz,则位移测量分辨率可达1 μm。     

GaAs-based fiber-optic pressure sensor

A new sensor developed for measurement of hydrostatic pressure up to at least 100 MPa at a standard range of ambient temperatures is described. The sensor exploits the displacement of the optical absorption edge occurring in semiconductors under the influence of hydrostatic stress as a result of pressure-induced energy shifting of conduction band extrema. The sensing element is composed of an intrinsically pure GaAs single crystal configured in the form of a microprism located at the sensor tip, and attached to two multimode (50/125 μm) optical fibers designed to deliver input light to the sensor and to output a pressure-modulated light signal to the outside of a pressure region. Characterization of the sensor has been performed for pressures up to 100 MPa and for temperatures ranging from 5 to 50°C. A procedure has been proposed involving the use of two sensors (active and compensating) to minimize temperature drift through appropriate signal processing     

A CMOS focal-plane motion sensor with BJT-based retinal smoothing network and modified correlation-based algorithm

This work presents and implements a CMOS real-time focal-plane motion sensor intended to detect the global motion, using the bipolar junction transistor (BJT)-based retinal smoothing network and the modified correlation-based algorithm. In the proposed design, the BJT-based retinal photoreceptor and smoothing network are adopted to acquire images and enhance the contrast of an image while the modified correlation-based algorithm is used in signal processing to determine the velocity and direction of the incident image. The deviations of the calculated velocity and direction for different image patterns are greatly reduced by averaging the correlated output over 16 frame-sampling periods. The proposed motion sensor includes a 32/spl times/32 pixel array with a pixel size of 100/spl times/100 /spl mu/m/sup 2/. The fill factor is 11.6% and the total chip area is 4200/spl times/4000 /spl mu/m/sup 2/. The DC power consumption is 120 mW at 5 V in the dark. Experimental results have successfully confirmed that the proposed motion sensor can work with different incident images and detect a velocity between 1 pixel/s and 140,000 pixels/s via controlling the frame-sampling period. The minimum detectable displacement in a frame-sampling period is 5 /spl mu/m. Consequently, the proposed high-performance new motion sensor can be applied to many real-time motion detection systems.     

用于换能器校准的激光干涉测振技术

本文介绍了用激光干涉仪对换能器表面振动位移进行绝对测量的原理,对不同情况下的信号处理方法进行了探讨,分别给出了低频及高频时的实验及进行信号处理后的结果。从实验结果及信号处理的结果可以看出,记系纹数的处理方法比较简单直观,而最大频率法则可解决小数条纹的测量。     

Signal processing and a groove baseband recording method to achieve a high-density optical disc

We propose a method for recording a multilevel signal onto optical read-only-memory discs. In this method we use signal processing to generate a multilevel recording signal that satisfies the zero-intersymbol interference condition and the zero-dc condition. The resultant multilevel signal is emboss recorded as the position displacement of groove walls. To play back a disc, push-pull detection and an adaptive equalizer are used. We also introduce feedback to reduce the nonlinear characteristics existing in the recording and playback systems. An experimental disc with 0.6-mum track pitch and 0.28-mum/bit density is made. When a digital versatile disc equivalent optical pickup is used to play back this disc, we confirm that a two-dimensional eye pattern of 16 levels is clearly observed.     

基于PC／104总线的飞机整流锥襟翼自动检查仪设计

为实时测量整流锥锥位和襟翼的收放角度,设计了基于PC/104总线的飞机整流锥襟翼自动检查仪;给出了硬件系统构成和各组成模块的功能,设计了信号调理、转换电路;利用Turbo C2.0构建的软件系统在DOS操作系统下实现整流锥和机动襟翼的自动检查以及检查数据的处理和显示;针对襟翼系统检查量大且复杂的特点,说明了襟翼自动检查的过程.使用结果表明,该检查仪满足根据大气参数自动检查整流锥和襟翼系统的需求,提高了检查效率与准确性.     

Axial nanodisplacement measurement based on astigmatism effect of crossed cylindrical lenses

Spot distortion caused by astigmatism effect in orthogonal cylindrical lenses is utilized to measure axial displacement with 30 nm resolution, strong noise immunity, and compact experiment setup. Axial displacement of the sample surface is determined by four-quadrant difference processing of distorted laser spots' energy distribution images received by CCD. Four-quadrant difference processing results indicate an applicable measuring range of 5.6 μm (cubic fitting r=0.9988) with a highly linear range of 1.2 μm (linear fitting r=0.9996). Factors affecting measuring range and sensitivity are analyzed by theoretical deduction and numerical simulation. This technique has potential applications in drifting sample tracking and measurement in advanced microscopy.     

Sinusoidal phase-modulating interferometer insensitive to intensity modulation of a laser diode for displacement measurement

In sinusoidal phase-modulating laser diode interferometers, an injection current of a laser diode is sinusoidally modulated to scan the laser wavelength. However, the modulation of the injection current also involves an intensity modulation of the light, which increases the measurement error if a conventional signal processing is used. A novel signal processing for displacement measurement is proposed to eliminate the influence of the intensity modulation. Numerical simulation results and experimental results make it clear that an optimal depth of the sinusoidal phase modulation exists that can reduce the measurement error to a few nanometers.     

全光纤速度干涉仪数据处理方法

准确地从试验数据计算输出信号相位差、振幅比及基线位置是 AFVISAR 数据处理程序所要解决的一项关键问题。通过对 AFVISAR 输出信号利萨如图形的深入研究,提出了一种自动拟合数据处理参数的算法。在借鉴传统速度干涉仪(VISAR)数据处理方法的基础之上,开发了AFVISAR 数据处理程序。运用该程序对 Hopkinson 压杆加载下的试验数据进行了处理,实测自由面速度的上升前沿和阻抗匹配法得到的结果相当一致。实测的速度最大值为 12.8m/s,与理论值13m/s 非常接近,表明该处理程序可以准确地、自动地拟合 AFVISAR 输出信号参数。     

纳米测量中的光栅信号细分技术

文章介绍了一种高精度位移测量方法,以LabVIEW作为工具,对高精度线性衍射光栅干涉仪(LDGI)的正交弦波信号进行采集、处理和分析,进行准确、快速的计数和细分,计算出精确的位移,并进行方向判断.以软件进行信号处理、位移计算,并对可能存在的信号异常进行纠错,简化了硬件,减少了电气环节引入的干扰.实验数据表明:该方法有效地进行高精度位移测量,标准差在20nm以下.     

A Novel Displacement Transducer Using the Second-Harmonic Type of Magnetic Modulator

A novel displacement transducer using the secondharmonic type of magnetic modulator is proposed to detect a static displacement as low as 0.1 ?m. The operation of transducer is based on modulating and amplifying the magnetizing force proportional to the input displacement by means of the second-harmonic type of magnetic modulator. In order to enhance signal sensitivity, 4 pole-pieces type dc bridge and differential type moving detector are used for modulation circuit of this transducer.     

刚体面内位移激光散斑测量研究

运用散斑统计理论,结合数字图像处理技术,设计了一套激光散斑测量刚体面内微小位移的实验系统,再利用刚体位移前后的散斑图像的互相关性,实现了刚体面内的位移测量.测量结果表明,针对刚体面内小于300μm的微小位移,x轴和y轴的绝对位移误差为±14μm,相对误差为±6.25%左右.     

基于多普勒效应的激光微位移测量系统

介绍了一种可进行动态微位移测量的激光微位移测量系统。该系统以多普勒效应为理论基础，以He-Ne激光器为光源，配置了判向变频系统、CCD视频信号的高速动态采集系统、微机处理系统及干涉图像处理软件包等，较传统测量方法其精度、误差、灵敏度及稳定度都有较大提高，并实现了微位移的全自动测量。     

测长表类自动检定仪

该仪器由一个以光栅为主的测量部分和一台作为控制用的微型计算机，打印机及计算机接口组成．一个合适测量范围的高精度光栅作为传感器，按照一定的方法使之符合阿贝原理．通过程序控制计算机，那么光栅的位移基本上就可以作为真值反映出被检表的位移量，该量通过计算机接口送到微机中去进行处理，然后打印出结果。研制此仪器的目的是为了解决百分表的自动检测问题，特别是大量程表的检测．该仪器不同于目前已有的用单片机控制的检定仪．它一是直观，二是不需要记忆，三是记录储存方便，四是可检定大量程百分表．该文章主要叙述了结构原理、程序编制、接口线路及误差分析几个部分．     

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.     

快速和高精度透视测量玻璃纤维/树脂复合材料构件内部的离面位移

提出一种光学干涉谱域相位对照B扫描,透视测量透明或半透明玻璃纤维/树脂复合材料内部离面位移的方法。针对玻璃纤维增强树脂基复合材料,设计了一种由树脂层模仿树脂基体、气隙层模仿裂缝气隙、玻璃层模仿玻璃纤维构成的树脂-玻璃复合构件,然后以此复合构件作为标定和量化系统的标准件进行实验研究。通过对平滑或散斑表面树脂-玻璃复合构件分别进行加载前后干涉光谱的两次拍摄,完成构件内部切面的离面位移测量,测量速度快。该系统的视场范围为3.5 mm、轮廓测量分辨率为±26.6 μm、离面位移测量精度为±0.1 μm、测量深度为2.66 mm。该方法在玻璃纤维增强树脂基复合材料力学性能测量和无损检测领域应用前景良好。     

Low-loss, silicon integrated, aluminum nitride photonic circuits and their use for electro-optic signal processing

Photonic miniaturization requires seamless integration of linear and nonlinear optical components to achieve passive and active functions simultaneously. Among the available material systems, silicon photonics holds immense promise for optical signal processing and on-chip optical networks. However, silicon is limited to wavelengths above 1.1 μm and does not provide the desired lowest order optical nonlinearity for active signal processing. Here we report the integration of aluminum nitride (AlN) films on silicon substrates to bring active functionalities to chip-scale photonics. Using CMOS-compatible sputtered thin films we fabricate AlN-on-insulator waveguides that exhibit low propagation loss (0.6 dB/cm). Exploiting AlN's inherent Pockels effect we demonstrate electro-optic modulation up to 4.5 Gb/s with very low energy consumption (down to 10 fJ/bit). The ultrawide transparency window of AlN devices also enables high speed modulation at visible wavelengths. Our low cost, wideband, carrier-free photonic circuits hold promise for ultralow power and high-speed signal processing at the microprocessor chip level.