基于干涉条纹移动量的非接触振动测量研究

为了实现大振幅、高带宽振动的非接触精密测量,本文提出了一种全新的光学测量系统.两束相干光的远场干涉条纹位置与两束光之间相位差有关,相位差的变化将引起干涉条纹移动.获取主条纹的位置,可以计算两束光之间的相位差,基于此可以还原物体的振动位移量.对振幅为10μm的单频余弦信号以及频率为44.1 kHz的声音信号仿真还原结果表明,本文所提光学系统和还原算法可以还原出亚微米级的振动信号,并能准确还原出音频信息.     

白光频闪散斑干涉术的研究

在利用白光对振动物体进行测量时,由于白光的相干性较差,难以得到质量较好的图像,为了克服这一缺点,本文提出了一种用白光光源照明进行振动测量的新方法-白光频闪散斑干涉术.阐述了白光频闪散斑干涉术的基本原理,分析了提高图象质量的主要原因,采用了相干性较好的白光光源和合理的光路,使系统的时间相干性和空间相干性得到提高,从而提高了图像的质量.实验结果表明,该方法用于振动的测量,能给出物体在任一瞬时的振动信息,得到清晰的、高对比度的全场干涉条纹图,图像的质量得到大大提高.     

激光干涉波形解调测量振动相位新方法

激光干涉频比计数法广泛应用于绝对法振动标准装置,针对频比计数法只能测量振幅不能得到振动相位,提出一种利用激光干涉条纹与振动台运动位移之间的关系,实现测量振动相位的新方法,并给出激光干涉波形解调测量振动相位的数学模型。该方法基于零差的迈克尔逊激光干涉仪,利用高速采集器同步采集激光干涉信号和传感器信号,并在Lab VIEW虚拟仪器开发平台上,软件解调振动波形,实现振动幅值和振动相位的实时测量。测量结果与正弦逼近法相一致。     

可判向光纤位移干涉仪在振动测量中的应用

提出了基于光学多普勒效应和外差方法设计的可判向光纤位移干涉仪,装置采用光通信行业中已经发展成熟的器件,主要有带尾纤的半导体激光器、1×2光纤耦合器、三端口环形器、光纤探头、3×3光纤耦合器、探测器以及示波器等构成.在原有结构的基础上,增加了光纤放大器和光纤滤波器,大大提高了信号光光强.结合李萨如图形给出了可判向光纤位移干涉仪的信号处理方法.利用该干涉仪测量了压电陶瓷的振动,实验表明能够测量的最小振动峰峰值为0.43 μm,并根据实验分析了干涉仪测量微位移的一些制约因素.研究表明,制约干涉仪测量微位移能力的主要因素是3×3光纤耦合器的非理想性,如3×3光纤耦合器输出干涉信号的位相差不恒定.     

一种新型位移与角度同时测量系统的设计

为了消除悬臂梁移动时产生的阿贝偏角误差,设计了一种可同时测量角度与位移的精密测量系统．首先,在激光干涉原理的基础上,通过改变光路将角度转换为可以反映干涉系统中光程差变化的位移量．其次,采用压电陶瓷（PZT）驱动柔性铰链机构,产生运动的干涉条纹．最后,采用四细分条纹计数辨向方法,进行运动干涉条纹的接收与处理实验,结果表明：在条纹宽度处于合适值时,系统满足了对阿贝偏角精密测量的要求．     

光纤干涉仪条纹动态测量技术

针对光纤干涉仪条纹的CCD动态测量技术,分析了限制条纹最大允许移动速度的因素,提出了采用中值滤波提高信号处理速度的方法。在条纹移动速度成指数增长时,实验观察了条纹位移测量值的变化情况,并进行了中值滤波实验。结果表明,条纹的最大允许移动速度除受CCD的场频和信号处理时间影响外,还与干涉仪使用的光源波长和光纤直径以及两光纤间的距离有关;中值滤波可以缩短信号处理时间,同时获得较好的滤波效果。     

科研

复旦大学全光纤纳米级多用测量系统研制成功复旦大学纳米技术发展中心光纤测量课题组开发的全光纤纳米级多用测量系统,采用光纤无源器件构造干涉光路,以普通光纤作为传感头,将被测试的微位移进行动态分段测试、合成,这种全新的方法具有传统干涉测量方法所不能比拟的优点。全光纤纳米级多用测量系统在位移测试量程方面不受限制,并已在实验室实现了100mm的测试量程,分辨率达到0.1nm数量级。此外,通过专门的处理软件,可实时反演测试量,并可基于对位移(应变)的实时测定获得对象的速度、加速度和振动情况,以及各种微应变,因此是一种纳米级精度的…     

一种新的正弦相位调制干涉条纹相位稳定方法

在基于条纹投射的物体表面形貌测量中,温度漂移和振动是造成条纹相位漂移的主要因素。为了稳定条纹相位,在相位补偿系统(PCS)中运用峰值检测简化相位提取过程,发展了一种基于正弦相位调制的干涉条纹相位稳定技术。将光纤缠绕在柱形压电陶瓷(PZT)上,向PZT注入正弦驱动电压实现对干涉条纹相位的正弦相位调制。运用2×2光纤耦合器分光,结合马赫-泽德干涉与杨氏干涉结构实现条纹投射。光电探测器检测两端面反射信号形成的迈克尔逊干涉信号,从中提取环境因素引起的相位漂移,运用旋转坐标数字机进行快速反正弦计算,生成的补偿信号与调制信号叠加后共同驱动PZT,实现条纹相位稳定。实验结果表明,条纹相位稳定精度为5.5 mrad,较好地消除环境因素引起的相位漂移。     

可调谐激光二极管在绝对距离干涉测量中的应用

可调谐激光二极管在绝对距离干涉测量中的应用Ｊ．Ｔｈｉｅｌ等１．前它传统的步进干涉仪仅允许测量反射镜的移动位移凸Ｌ，该位移量由下式给出：ＡｂＬ＝Ａｇｂ·５５－－（１）其中激光波长Ｋ。７８０ｕｒｎ，而西中为探测到的干涉条纹数。静态距离Ｌ。。ｓ的测量方法是...     

一种正弦相位调制光纤干涉条纹相位稳定方法

为了消除环境因素(尤其是振动和温度波动)在物体表面三维形貌测量中的影响,基于正弦相位调制(SPM)发展了一种光纤干涉条纹相位稳定技术。利用马赫-泽德光纤干涉仪结构和杨氏双孔干涉原理实现高密度的余弦分布干涉条纹投射。利用两光纤干涉臂端面的菲涅尔反射生成迈克尔逊干涉信号,由光电探测器(PD)检测后送入相位控制系统。采用相位生成载波的方法提取干涉信号的相位,并将生成的补偿信号闭环反馈给压电陶瓷驱动器,与正弦相位调制信号相加后共同驱动压电陶瓷,补偿环境因素带来的相位漂移,实现干涉条纹相位的稳定。环境因素对条纹相位的影响低于57 mrad,实验结果验证了该方法可行性。     

Spatial resolution enhancement of fiber-optic scanning white-light interferometer by use of a Vernier principle

A Vernier principle is employed to improve the spatial resolution of a fiber-optic white-light interferometer to the accuracy of 0.2 microm. The Vernier principle is implemented by combination of interference fringes itself and a virtual fringe that is generated by means of software tracing the scanning mirror. Two rulers are read with respect to each other. This design is insensitive to intensity fluctuation of the interference fringe. The applications, submicrometer estimation for the quadrature-locking selection and the tolerance of the relative measurement, demonstrate its effectiveness.     

Assessment of a multibeam Fizeau wedge interferometer for Doppler wind lidar

The Fabry-Perot interferometer is the standard instrument for the direct detection Doppler lidar measurement of atmospheric wind speeds. The multibeam Fizeau wedge has some practical advantages over the Fabry-Perot, such as the linear fringe pattern, and is evaluated for this application. The optimal Fizeau must have a resolving power of 10(6) or more. As the multibeam Fizeau wedge is pushed to such high resolving power, the interference fringes of the device become complicated by asymmetry and secondary maxima. A simple condition for the interferometer plate reflectance, optical gap, and wedge angle reveals whether a set of parameters will yield simple, Airy-like fringes or complex Fizeau fringes. Tilting of the Fizeau wedge improves the fringe shape and permits an extension of the regime of Airy-like fringes to higher resolving power. Sufficient resolving power for the wind lidar application is shown to be possible with a large-gap, low-finesse multibeam Fizeau wedge. Liabilities of the multibeam Fizeau wedge in the wind lidar application include a smaller acceptance solid angle and calibration sensitivity to localized deviations of the plates from the ideal.     

Measurement of air turbulence for on-machine interferometry

There is increasing demand for in situ shape measurements performed on ultraprecision processing machines. One major source of error during interferometric measurements performed on machines is fringe displacement due to external disturbances. We have developed an interferometer equipped with an electro-optic phase modulator that measures the phase of interference fringes before they are displaced by air turbulence. The frequency characteristics of air turbulence induced by a heat source are derived from successive measurements of a test surface. Experimental results show that the phase of the interference fringes can be accurately measured in the presence of air turbulence when the intensity of the fringes is sampled at a speed of several hundred hertz.     

Measuring the refractive indices of liquids with a capillary tube interferometer

A theoretical analysis of the fringe pattern produced by a capillary tube interferometer is presented, which is expected to be two-beam interference, and a computer program to simulate the interference fringe pattern is established. By comparing the simulated fringe pattern and the experimental fringe pattern, the refractive index of the liquid can be given when the two fringes coincide best. The results of this method are close to those of the Abbe refractometer.     

Two-dimensional surface profile imaging technique based on a double-grating frequency shifter

A two-dimensional surface profile imaging technique that uses a low-coherence heterodyne interferometer is proposed. A double-grating frequency shifter was used in a tandem interferometer to provide the achromatic frequency shift for low-coherence light. A chopper, together with a processing circuit, was implemented to modulate the interference fringes. The surface profile was measured from the interference fringes taken by a CCD camera using a five-step method. The uncertainty in the displacement measurement is 0.34 microm for a displacement range of 43 microm. The surface profile of a glass sample with low effective reflectivity was acquired.     

Intermodal interferometer for strain and temperature sensing fabricated in birefringent boron doped microstructured fiber

We present a compact in-line fiber interferometric sensor fabricated in a boron doped two-mode highly birefringent microstructured fiber using a CO(2) laser. The intermodal interference arises at the fiber output due to coupling between the fundamental and the first order modes occurring at two fiber tapers distant by a few millimeters. The visibility of intermodal interference fringes is modulated by a polarimetric differential signal and varies in response to measurand changes. The proposed interferometer was tested for measurements of the strain and temperature, respectively, in the range of 20-700?°C and 0-17?mstrain. The sensitivity coefficients corresponding to fringe displacement and contrast variations are equal respectively for strain -2.51 nm/mstrain and -0.0256 1/mstrain and for temperature 16.7 pm/°C and 5.74×10(-5) 1/°C. This allows for simultaneous measurements of the two parameters by interrogation of the visibility and the displacement of interference fringes.     

一种基于Matlab的干涉条纹自动处理方法

对接触式干涉仪量块检定时产生的两种干涉条纹进行了研究,图像整体采用傅里叶级数曲线拟合法,实现干涉暗条纹大致定位.局部采用最小二乘二次曲线拟合法,确定干涉暗条纹中心的精确位置及暗条纹个数.利用Matlab和VC平台进行编程,快速有效地实现了干涉条纹中心位置的自动判读. 该方法已应用在中国计量科学研究院接触式干涉仪的量块检定中.     

Simultaneous measurement of multiparameters using a Sagnac interferometer with polarization maintaining side-hole fiber

A Sagnac interferometer with a section of a polarization maintaining side-hole fiber for multiparameter measurement is proposed. The sensor was experimentally demonstrated to be sensitive to torsion, temperature, and longitudinal strain, simultaneously. The birefringence in the investigated side-hole fiber is induced simultaneously by the elliptical shape of a germanium-doped core and by field overlap with the air holes surrounding the core. The latter effect is purely geometrical and causes high chromatic dispersion of the group birefringence in the long wavelength range, which results in a different period of spectral interference fringes. A different wavelength response is obtained for each interference fringe peak when the fiber is subjected to torsion, temperature, or longitudinal strain. A matrix equation for simultaneous measurement of the three parameters--torsion, temperature, and longitudinal strain--is also proposed.     

Development of a line-scan CCD-based fringe tracker for optical interferometry

Traditional high-precision optical techniques, such as interferometry, are in ever-greater demand for noncontrolled environments. This is the case for the UPC-ZEBRA, a large-aperture interferometer that was built to measure vertical discontinuities (i.e., piston errors) in segmented mirrors. The large mechanical systems used to drive the interferometer to the different measurement positions generate perturbations that are highly incompatible with the expected piston measurements on the nanometer scale. We introduce a new system based on a line-scan CCD to track interference fringes. The error signal obtained from this fringe tracker has been used in a closed-loop control system to actively stabilize the interferometer. The perturbation has been attenuated by a factor of 1/200.