基于光纤法珀干涉仪偏置点控制的高频振动位移测量方法

为了实现超声换能器辐射面的振动测量,本文研究了一种基于光纤法珀干涉仪偏置点控制的高频振动位移测量方法,具有抗环境干扰、精度高等优点.针对正交相位偏置点解调方法中偏置点不稳定的问题,提出并分析了一种采用压电陶瓷叠堆执行器调整腔长稳定偏置点的工作原理,并对高频振动位移测量系统的性能进行了实验测试.实验结果表明:通过反馈控制腔长可以实现法珀干涉仪相位偏置点的稳定;位移测量系统的位移分辨率高于0.229nm;测得位移和换能器的输入电压的非线性度小于3.41%.     

Mach-Zehnder光纤干涉仪相位载波调制及解调方案的研究

本文根据Mach Zehnder光纤干涉仪相位调制与双光束干涉测量的特点 ,提出了一种采用相位调制器 (PZT)实现相位载波调制 ,利用贝塞耳函数进行傅里叶分解实现相位调制信号解调的检测方案。理论分析表明 ,该方案能有效地抑制随机干扰信号对测量精度的影响     

基于非本征F-P干涉技术的全光纤位移测量系统北大核心CSCD

为解决传统分离镜组式干涉仪体积较大,无法在空间受限的环境条件下应用的问题,开展了全光纤F-P干涉位移测量技术研究。根据干涉原理分析了不同反射率条件对干涉信号形式的影响,计算得出:当反射率为4%时,多光束干涉的光强信号将近似为正弦函数,并利用有限元仿真对位移测量原理进行验证。设计搭建了基于非本征F-P干涉技术的全光纤位移测量系统。实验结果表明:该系统在1 min内静态噪声电压标准差为23.3 mV;在1 mm位移范围内,该系统与XL-80激光干涉仪的测量结果呈现高度线性关系,线性相关系数R 2为1,且该系统位移测量重复性优于XL-80激光干涉仪。     

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.     

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。     

激光干涉仪误差修正系统的设计

基于谐波分离修正算法,采用高速可编程器件,构建了一套激光干涉仪误差修正系统.该系统通过校准过程建立误差修正方程,并生成修正相位表.测量时数据采集及处理单元的可编程器件实现定点型移位相减除法运算,得到数字化的正切值,将正切值作为内存地址,通过硬件查表得到修正相位值,极大提高了误差修正速度.并分析了定点型移位相减除法精度以及寻址空间大小对系统误差的影响.     

高精度衍射光栅干涉仪的研制

提出了一种新型的激光衍射光栅干涉仪测量系统,以光栅衍射原理和偏振光学为理论基础,配合正交信号的解相位细分原理,使得该系统可以达到纳米级分辨率.由于光栅干涉测量系统以光栅栅距作为测量基准,相对于传统干涉仪,光栅尺系统受环境因素造成的测量误差影响较小.通过实验校正,得到不同行程范围内光栅干涉测量系统的纳米级重复性误差,新型的激光衍射光栅干涉仪测量系统适合于较长行程的高精度位移测量.     

高精度位移传感器测量

利用高精度的F-P激光干涉仪,研制了一套用于高精度位移传感器的校准装置,可以校准示值误差为十几个纳米到几十个纳米的高精度位移传感器.测量原理是利用F-P激光干涉仪的灵敏度高、测量精度高等特点,将干涉仪和被测传感器同时测量放置在精密位移工作台上,通过比较激光干涉仪移动镜的位移量和被测传感器的位移量间的差异,得出被测传感器的线性,整个测量过程完全由计算机控制.该系统测量范围为0～25mm,测量不确定度为6 nm+l/2 nm(k=1).     

光纤外差干涉位移传感器

非接触式光纤外差干涉位移传感器是将半导体激光器线性调频技术和光纤传感技术相结合制成的1种新型外差干涉仪。它的位移测量范围可达26mm，分辨率为0．02μm；对不同材料、不同粗糙度的对象面，有着几乎相同的测量灵敏度和测量精度；探头和对象面无需严格垂直。     

光纤出射光强分布研究

对多模光纤出射光束的光强分布用横向位移法进行了理论分析和实验研究,并用数值计算的方法分析实验测量数据.结果表明,高斯光束可以很好地描述光纤出射光强的分布,光纤出射光束光强分布参数主要与光纤芯径和出纤光功率等有关,为强度调制型光纤传感器的优化研制提供了必要的实验依据.     

1 550 nm全光纤激光多普勒测振系统研制

针对目前国内激光测振系统价格昂贵、使用不便的问题,采用1 550 nm波段成熟的窄线宽光源和光纤元器件研制了一套低成本的全光纤激光测振系统原理样机。此原理样机光路部分采用马赫?泽德干涉仪结构,搭建了外差式激光干涉光路,参考光被40 MHz的声光调制器调制,与测量光在光电探测器表面发生干涉,产生原始的激光多普勒信号;信号解调部分采用相位解调法对原始激光多普勒信号进行解调,得到振动目标的运动特性,包括位移、速度和加速度信息。采用本单位的振动标准装置对其性能进行了测试,实验结果表明：在10 ~ 2 000 Hz的中低频振动范围内,1 550 nm全光纤激光多普勒测振系统峰值位移、速度和加速度的测量误差在-0.6% ~ 0.7%内。该系统在中低频段具有较高的测量准确度,且成本相对较低、操作便捷,具有技术借鉴价值。     

共路激光干涉测量系统的研究

激光干涉测量系统在精密测量领域占有重要地位,它对温度变化、大气变化、激光波长变化、机械安装误差和外界振动等比较敏感,影响系统的测量精度和稳定性。针对此情况,该文提出一种新型的激光干涉光路,两光臂呈完全共路结构,使干涉条纹信号具有极强的抗干扰能力;对光路进行抗干扰分析和理论推导;构建位移测量系统,进行系统测试实验和误差分析。实验表明,本系统测量分辨力0.72nm,合成标准不确定度5．2nm（k=2）,运行速度0．56mm／s,量程0．01mm。     

Precise interferometric AO method for SAW velocity measurements inan anisotropic solid

We suggest an original method utilizing a two beam optical interferometer for the accurate SAW velocity measurements in an anisotropic solid. Namely, two parallel and spatially separated optical beams are diffracted from different points along the path of SAW propagation. Then at the output of the interferometer light beams of different orders (0, ±1) reflecting from the surface with SAW are combined in pairs to create the interference patterns. Measurement of the interference pattern's intensity oscillations versus the SAW frequency gives all needed information to determine the phase and the group SAW velocities and their dispersion. Experimental software includes: statistical data accumulation with auto correction of the interferometer phase change caused by a change of the external conditions, and Fourier analysis of interferometer signal spectrum with the use of generalized variables taking into account the SAW dispersion. The experimental error depends on the experimental peculiarities and is about 0.5 m/s for the phase velocity and 3 m/s for the group velocity. The method is tested by SAW velocity measurements on ST-quartz with a thin film of Al     

Development of speckle shearing interferometer error analysis as an aperture function of wavefront divergence

Increasing the confidence in whole-field speckle-based optical metrology transducers requires a detailed understanding of the error sources of the respective instruments. The analysis of error contributions to the optical phase output of a Michelson-based speckle shearing interferometer have been modelled. Specific attention has been paid to the effect of the aperture at the image plane, with respect to collimated and non-collimated object illumination. This modelling presents an advance on a previous modelled analytical relationship, which includes partial displacement derivative terms and components as a function of illumination geometries and, importantly, aperture effects. The work has identified a phase error contribution due to the aperture function of between 0.15% and 1.48%, dependent on the object distance, when considering a planar object undergoing predominantly surface to normal deformation.     

Research on horizontal displacement monitoring of deep soil based on a distributed optical fibre sensor

The traditional measurement method for the horizontal displacement of deep soil usually uses an inclinometer for piecewise measurement and then generates an artificial reading, which takes a long time and often contains errors; in addition, the anti-jamming and long-term stability of the inclinometer is poor. In this paper, a technique for monitoring horizontal displacement based on distributed optical fibres is introduced. The relationship between the strain and the deflection was described by a theoretical model, and the strain distribution of the inclinometer tube was measured by the cables laid on its surface so that the deflection of the inclinometer tube could be calculated by the difference algorithm and regarded as the horizontal displacement of deep soil. The horizontal displacement monitoring technology of deep soil based on distributed optical fibre sensors developed in this paper not only overcame the shortcomings of traditional inclinometer technology to realize automatic real-time monitoring but also allowed for distributed measurement. The experiment was similar to the expected engineering situations, and the deflection calculated from the strain was compared with an inclinometer. The results demonstrated that the relative error between the distributed optical fibre sensors and the inclinometer was less than 8.0%, and the results also verified both the feasibility of using distributed optical fibre to monitor the horizontal displacement of soil as well as the rationality of the theoretical model and difference algorithm. The application of distributed optical fibre in monitoring the horizontal displacement of deep soil in the engineering of foundation pits and slopes can more accurately evaluate the safety of engineering during construction.     

Parabolic liquid mirrors in optical shop testing

A parabolic liquid mirror obtained by the rotation of a mercury bath around a vertical axis has been built and its optical surface characteristics measured to demonstrate that it can be used in optical shop testing as a reference surface. A linear Hartmann test allowed us to check that the focal length is well related to the rotation velocity, following the theory, and that no spherical aberration is present, as assumed by previous authors. The spherical aberration has been found to be smaller than λ/50 at 633 nm. An interferometric test of the mirror compared with a null lens gave information about the quality of the optical surface for which the rms wave-front error, when the random errors are averaged, is ~λ/25. Because modifying the mirror diameter is cheap and fast and adjusting its focal length within a large range is straightforward, the parabolic liquid mirror can become a highly adaptable tool in optical metrology. In particular, it can be used in optical shop testing as a reference surface to test null correctors, to check any system developed to control the shape of large parabolic or quasiparabolic top-quality solid-state mirrors, or to make holographic references of such surfaces.     

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.     

运动参量校准装置系统的研制

摘 要：为了对运动参量测试设备进行校准,研制了一套双曲柄连杆耦合运动装置。通过两套变频调速伺服电机进行运动控制,产生了大范围可调的动态位移、速度、加速度等运动参量。通过4通道高速采集卡和工控机完成全程运动参数的精确测量和运动误差分析。在设计机械结构、控制系统和信号测量系统的基础上,提出了一种基于时间共轭的超前反馈控制算法和基于相位比较的测量方法。测试结果表明速度、加速度的测量误差小于1%。该校准装置可以用于运动测试设备的校准。     

面波法检测地基波速中振源与测点的布置方法

在地面竖向简谐集中力作用下,利用轴对称有限元-无限元耦合模型计算了地表动力响应的相频特性,并由此系统地考察了由两点相位差确定R波速度的影响因素及其规律性。对匀质弹性地基的研究结果表明,为保证由不作P波和S波滤波处理的实测地表信号相位差求出的R波速度具有足够高的精度,点-源距和测点间距必须满足一定的要求;对高饱和度地基及当测点间距较小时,目前对振源和测点布置的常见做法会使检测结果出现较大的误差。结论对地基波速检测的面波法现场工作方法具有重要的指导意义。     

磷酸二氢钾晶体薄表面层生长动力学实时显微研究

利用光学显微镜实时观测磷酸二氢钾(KDP)晶体柱面及锥面薄表面层的生长过程,测得不同过饱和度下薄表面层前端不同倾角的非正常棱边推移速度。结果表明:倾角越小,非正常棱边推移速度越慢,薄表面生长终止于其前端的正常棱边处;随着过饱和度的增大,非正常棱边推移速度线性增加。计算得到柱面及锥面薄表面层前端非正常棱边推移动力学系数,由于Eslice(010) Eslice(101),因而柱面薄表面层的生长动力学系数大于锥面。建立了基于非奇异面上台阶生长机制下的薄表面层生长体扩散模型。应用该模型解释了薄表面层生长速度随其厚度及前端非正常棱边倾角的变化关系,并讨论了溶液流动对薄表面层生长的影响。结果发现薄表面层生长存在一个使其以恒定厚度向前推移的临界厚度。