共查询到20条相似文献,搜索用时 15 毫秒
1.
A modified two-aperture speckle shear interferometer that eliminates the contribution of the in-plane component and its derivative to the phase change, and yields a fringe pattern corresponding to the first-order partial derivatives of the out-of-plane displacement component, is reported in this note. In this method, two laterally sheared object points are viewed axially. The wave fields from these points are independently combined at the image plane of the imaging system. 相似文献
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Lucas P. Tendela Alejandro FedericoGuillermo H. Kaufmann 《Optics and Lasers in Engineering》2011,49(2):281-284
This paper presents an interferometric measurement of the out-of-plane deflections produced by a piezoelectric transducer, manufactured by thick-film deposition of a ceramic paste over an alumina substrate, when is subjected to a DC electric voltage. It is shown that a digital speckle pattern interferometer with an incorporated phase-shifting facility allows the measurement of nanometer displacements generated by the piezoelectric device. These measurements are used to evaluate the effective piezoelectric charge constant along the polarization direction (d33)eff that characterizes the thick-film transducer. 相似文献
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The analysis of in-plane rigid-body rotations requires phase-shifting methods to determine the direction of rotation in conventional electronic speckle pattern interferometry (ESPI). The phase-shifting procedure makes the real-time measurements impossible. A quasi-real-time method is published recently, where the usual symmetric illumination is combined with a wavelength change before the second exposure. The present paper proposes a device sparing an alternative to this. The symmetric illumination is retained but the wavelength change is replaced by simple illumination direction changes. 相似文献
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An interferometer is described in which a rotatable Wollaston prism is used to achieve constant radial and azimuthal shears in a converging beam. These displacements may have applications in speckle shearing interferometry for the deformation measurement of objects with axial symmetry. 相似文献
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Ping Sun 《Optics Communications》2007,275(2):305-310
A fringe carrier method for separating out-of-plane displacement from in-plane components based on large image-shearing electronic speckle pattern interferometry (ESPI) is presented. If the test object is respectively illuminated by two expanded symmetric illuminations in large image-shearing ESPI, two interferometers are formed. Carrier fringe patterns can be introduced by tilting reference surface a small angle. The carrier fringe patterns are demodulated after deformation of the object. Two phase maps, which include out-of-plane and in-plane displacement, can be obtained by using Fourier transform. Then out-of-plane displacement can be easily separated from in-plane displacement by simple operation between two unwrapped phase distributions. The principle of spatial carrier frequency modulation in large image-shearing ESPI is discussed. A typical three-point-bending experiment is completed. Experimental results are offered. The results show that the method offers high visibility of carrier fringes. And the system presented does not need a special beam as a reference light and has simple optical setup. 相似文献
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A review on refractive index and temperature profile measurements using laser-based interferometric techniques 总被引:5,自引:0,他引:5
In this review we have discussed laser-based interferometric techniques for measurement of refractive index, temperature and temperature profile of burners with special emphasis on laser speckle techniques and Talbot interferometric technique. 相似文献
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Theoretical analysis and experiments prove that there is a random phase error in the measurement of the in-plane displacement of solid surfaces by laser Doppler velocimetry. This error will impede the accuracy of the measurement from being further improved to, for example, the region of several fractions of one order. In addition, the reason for the random signal dropout in the measurement is also studied and a method of extending the range in which the signal is maintained continuous is also given. 相似文献
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Gray Malcolm B. McCLELLAND David E. Barton Mark Kawamura Seiji 《Optical and Quantum Electronics》1999,31(5-7):571-582
A small Michelson interferometer has been configured as a tracking mirror displacement sensor in order to achieve both large dynamic range (2.1 mm) and excellent sensitivity
across a broad frequency range (6Hz–3 kHz). The interferometer is illuminated by a simple LED, uses broadband, non-polarising beamsplitters and contains no lensing optics. A DC-coupled balanced detector provides an error signal that is used to position the tracking mirror of the Michelson interferometer so as to maintain an interferometer operating position close to the centre of a particular fringe. The total interferometric sensor provides a small, simple and cost-effective means of achieving high-resolution displacement measurements. 相似文献
11.
A non-linear control method, known as Variable Structure Control (VSC), is employed to reduce the duration of ultrasonic (US) transducer transients. A physically realizable system using a simplified form of the VSC algorithm is proposed for standard piezoelectric transducers and simulated. Results indicate a VSC-controlled transmitter reduces the transient duration to less than a carrier wave cycle. Applications include high capacity ultrasound communication and localization systems. 相似文献
12.
A powder diffractometer with a linear position sensitive detector (PSD) has been designed and fabricated at BARC. The system
is in operation at Dhruva reactor. The PSD has been tested for the position linearity and the uniformity of efficiency. The
resolution Δd/d of the diffractometer has been found to be 1·3%. The data can be analyzed using profile refinement technique. 相似文献
13.
A signal processing scheme using a curve fitting algorithm to determine the central position of the digitized fringe pattern output of a white light interferometric (WLI) system is discussed. An analytic result for the resolution obtained in the central fringe position measurement using a specific curve fitting scheme has been given and a simulation of the measurement of the central position of a computer generated fringe pattern has been carried out. The results from the simulation show good agreement with those from the theoretical analysis. A supporting experiment to investigate this effect has also been carried out and the short term repeatability of the central position measurement using the curve fitting scheme gives close agreement with the theoretical results. 相似文献
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In this paper, the 2-D electrostatic field software, POISSON, is used to calculate the characteristic impedance of a BPM (beam position monitor) for a high current proton linac. Furthermore, the time-domain 3-D module of MAFIA with a beam microbunch at a varying offset from the axis is used to compute the induced voltage on the electrodes as a function of time. Finally, the effect of low 13 beams on the induced voltage, the sensitivity and the signal dynamic range of the BPM are discussed. 相似文献
16.
RF cold test of a novel C-band cavity beam position monitor (PBM) to be used in the SDUV-FEL Test Facility is described. The test results are presented and some characteristics discussed. The main parameters obtained are in reasonable agreement with the analytical estimations. Effective suppression of the common mode has been demonstrated. The position sensitivity over the test region of ±0.5 mm is about -21.58 dB/10 μm for the TM110 mode and is linear in the central region of the BPM cavity. 相似文献
17.
In this paper, the 2-D electrostatic field software, POISSON, is used to calculate the characteristic impedance of a BPM (beam position monitor) for a high current proton linac. Furthermore, the time-domain 3-D module of MAFIA with a beam microbunch at a varying offset from the axis is used to compute the induced voltage on the electrodes as a function of time. Finally, the effect of low β beams on the induced voltage, the sensitivity and the signal dynamic range of the BPM are discussed. 相似文献
18.
本文提出了一种抑制合成孔径雷达图像乘性相干斑噪声的各向异性扩散滤波新方法.该方法将受自适应耦合函数控制的平均曲率运动嵌入到传统相干斑抑制的各向异性扩散方程中,形成了一种可有效抑制边缘区域相干斑与同质区块效应现象的各向异性扩散新方程,同时在新建的扩散方程中,引入了由改进Frost滤波与局部方向比率联合构建的一种带方向约束的新扩散函数,进一步削弱了块效应现象且明显改善了抑斑图像的边缘抖动扭曲问题.实验结果表明该方法在有效保护图像边缘的同时,能充分平滑同质区与边缘区域的相干斑,明显削弱块效应现象,有效改善抑斑图像边缘抖动扭曲问题,而抑斑图像无论视觉效果还是参数指标均比多种传统抑斑方法更具优势. 相似文献
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Zhiwei Men Wenhui Fang Zuowei Li Guannan Qu Chenglin Sun Shuqin Gao Guohui Lu 《Journal of Raman spectroscopy : JRS》2010,41(12):1661-1663
We present a simple analytical model to describe the stimulated Raman Stokes scattering (SRS) linear polarization spectroscopy of fluorescent dye solutions in liquid‐core optical fibers (LCOFs). In this scheme, the linear polarization direction of the pump pulse is set parallel to the y‐axis through a straight polarization‐maintaining LCOF, in which the energy of the total optical field is kept invariant, and different fluorescence dyes are used to generate different first‐order Stokes intensities. We demonstrate the SRS of all‐trans‐β‐carotene and fluorescein in carbon disulfide (CS2) solutions due to the optical field‐induced reorientation effect, which makes the first‐order Stokes polarization direction rotate by an angle of 88° or 61°, respectively. This demonstrates the good agreement between the theory presented and the experiment. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献