Non-contacting laser based displacement measurements from solid objects

This note reports a laser Doppler interferometer for measuring the axial motion of solid targets which have had no prior preparation. Both magnitude and sense of motion are measured to a resolution at least 0.316 μm usinga passive optical system and simple signal processing, making the device relatively cheap to construct. Results indicate that the LDI is capable of good linearity over a substantial range of target amplitudes and has a reasonable degree of immunity from speckle effects.     

Entanglement and Non-Locality in Quantum Protocols with Identical Particles

We study the role of entanglement and non-locality in quantum protocols that make use of systems of identical particles. Unlike in the case of distinguishable particles, the notions of entanglement and non-locality for systems whose constituents cannot be distinguished and singly addressed are still debated. We clarify why the only approach that avoids incongruities and paradoxes is the one based on the second quantization formalism, whereby it is the entanglement of the modes that can be populated by the particles that really matters and not the particles themselves. Indeed, by means of a metrological and of a teleportation protocol, we show that inconsistencies arise in formulations that force entanglement and non-locality to be properties of the identical particles rather than of the modes they can occupy. The reason resides in the fact that orthogonal modes can always be addressed while identical particles cannot.     

Phase-stepped ESPI and moiré interferometry for measuring stress-intensity factor andJ integral

Electronic-speckle-pattern interferometry and moiré interferometry have been used to calculateK ₁ andJ for compact tension specimens. Automated-fringe-pattern analysis enables the full-field of data to be used with the minimum of operator intervention. Measurements are shown to be accurate to within 10 percent. TheJ-measurement procedure employed could form the basis of an automatic-fault detection system.     

夹层全息干涉法的残余应力测试

本文用夹层全息干涉法做了模拟残余应力的标定实验,测试了焊缝、铸件的残余应力,并且利用数值方法进行了定量分析,实验结果与理论值比较吻合。     

剪切散斑干涉与有限元优化计算相结合实现缺陷参数的定量求解

本文将剪切散斑干涉与有限元优化分析相结合，对薄壁压力容器缝缺陷进行了定量检测，通过对优化计算结果和已知的缺陷参数所构成的目标函数的求解，获得了较为精确的缺陷参数识别结果。     

部分相干光云纹干涉法测三维位移场

本文提出了一种用部分相干光可同时获得面内位移和离面位移场的云纹干涉法。该法具有装置简单,无需防震,可用于观场测量等特点。文中论述了此法的基本原理,应用波前干涉理论和付里叶光学理论对变形前后波前的干涉、记录和再观进行了分析,导出了计算公式。实现了透射物体和反射物体表面的面内位移分量(U_0,V_(45),U_(90))和离面位移(w)的全场同时测量,典型实验证明,实验值与计算结果符合较好。     

Dispersion measurement of liquids with a fiber optic probe based on a bi-functional lensed photonic crystal fiber

We report a fiber optic probe suitable for measuring the wavelength dispersion of liquids. The measuring probe is made from an extrinsic fiber-optic cavity formed by a lensed photonic crystal fiber (PCF) and a micro-mirror. The custom-designed lensed PCF plays a dual role of collimator to help realize a long cavity length of the order of millimeters and as an efficient reflector to form the reference beam. The length of the cavity used in the experiment is about 1620 μm. In this article, we present the analytical method of obtaining dispersion of the liquid sample from the spectral interferogram of a single-arm or common path interferometer. Sodium chloride salt solutions with varied concentrations are used as an example to demonstrate the efficacy of the instrument. The index change with concentration is found to be linear at low concentrations and deviates from linearity as it approaches saturation.     

Diffraction errors in micromirror-array based wavefront generation

Using Laser-based Speckle-Interferometers, the shape of optically rough surfaces can be measured precisely and contactlessly from variable measuring distances even in regions of difficult access. This work is concerned with the integration of a micromirror array (MMA) into an electronic Speckle-Pattern-Interferometer. With the adaptive optics, it is intended to adapt the phasefront of a reference wave to critical surface areas of the measurement object. Yet, due to the topography of the MMA, diffraction effects occur which affect the phase and intensity of the generated wavefront. We demonstrate how these diffraction effects can be efficiently modelled by a Fraunhofer diffraction method. We compare the results of this model to theoretical data obtained by a numerical Fresnel diffraction model and to measurement data obtained from a measurement setup incorporating a multi mirror array.     

Quadrature demodulation technique for self-mixing interferometry displacement sensor

A new, to the best of our knowledge, signal processing method based on quadrature demodulation technique is presented for laser diode self-mixing interferometry(LDSMI) displacement sensor. Phase modulation of the laser beam is obtained by an electro-optic modulator (EOM) in the external cavity. Detection of the target's displacement can be easily achieved by sampling the interference signal at those times which satisfied certain conditions. The major advantage of the technique is that it does not involve any complicated calculation and insensitive to the sampling error. Experimental results show that the proposed method can effectively improve the displacement measurement resolution of the laser diode self-mixing displacement sensor to a few nanometers.     

基于低通滤波的相位掩模干涉图相位解调方法

 传统的四步相移算法在分析相位掩模干涉图时存在相移值误差、分辨力降低和相干噪声等不足,从而影响了动态干涉仪的性能。为了提高相位掩模干涉图的分析精度,提出了一种基于低通滤波的相位解调方法。该方法根据相位掩模引入相位的空间频率远大于被测相位空间频率的最大值,采用低通滤波的方法提取相位信息。数值分析结果表明,该方法的精度高于传统四步相移算法。分析干涉图的信噪比,合理选择低通滤波器,可进一步提高相位解调的精度。