共查询到20条相似文献,搜索用时 500 毫秒
1.
激光多普勒测速仪检测系统提取的光电信号中存在较大的噪声信号。为了消除这些噪声干扰, 提高激光多普勒测速仪的测量精度,提出一种新的信号处理方法,将最小均方差自适应滤波技术应用于激光多普勒测量中,利用多普勒信号和噪声信号的统计特性,以最小均方误差估计为准则,最大程度地滤除噪声信号。阐述了最小均方差自适应滤波算法的基本原理,在MATLAB平台上将其应用于理想正弦信号进行仿真,并将其应用于实测多普勒信号的处理中。仿真和实验均表明,该技术可以有效抑制激光多普勒测量中的多频率噪声的干扰,大大提高多普勒信号的信噪比和测量精度,为设计高精度的激光多普勒测速仪创造了条件。 相似文献
2.
The common method of laser Doppler velocimeter (LDV) signal processing is fast Fourier transform (FFT). Because of the restraint of spectral interference, fence effect and spectrum leakage, the precision of FFT is not high. In order to improve the accuracy of double-beam and double-scattering laser Doppler velocimeter signal processing, an algorithm based on spectral refinement and interpolation is put forward. First, high-pass filter is adopted to remove the baseplate of LDV signal. Second, FFT is adopted to get the estimate of Doppler frequency and then Zoom-FFT is used to refine the local range of Doppler frequency. Third, four-term fifth derivative Nuttall windowed interpolation is used to correct the refined spectrum. Then the accurate estimate of Doppler frequency can be obtained. Simulations and experiments based on the LDV system built in laboratory show that Zoom-FFT can improve the resolution of spectrum and four-term fifth derivative Nuttall windowed interpolation can further increase the precision of signal processing. 相似文献
3.
Emilia Mihaylova Izabela Naydenova Barry Duignan Suzanne Martin Vincent Toal 《Optics and Lasers in Engineering》2006,44(9):965
In this paper we present an electronic speckle pattern shearing interferometer using a photopolymer diffractive optical element in the form of a holographic grating, in combination with a ground glass to shear the images. The sheared images on the ground glass are further imaged onto a CCD camera. The distance between the grating and the ground glass can be used to control the shear and to vary the sensitivity of the system. The direction of sensitivity is easily controlled by rotation of the diffraction grating around its normal.Introducing photopolymer holographic gratings in ESPSI gives the advantage of using high aperture optical elements at relatively low cost. The fact that the diffractive optical element is a photopolymer layer on glass substrate with thickness of 2 mm makes for a compact optical system.The system was successfully used for detection of the resonant frequencies of a vibrating object.Most of the published work on vibration analysis is analytical. Very few experimental results are available in the literature. The well known laser Doppler vibrometers (LDV) and accelerometers used for modal analysis are pointwise measurement techniques, although multipoint LDV is available at significant cost.Electronic speckle pattern techniques suitable for experimental detection of the resonant frequencies of vibrating objects are very promising for vibration analysis because they are whole field and non-contact.A finite element model is developed for prediction of the vibration modes of the object under test. Detection of vibrational modes of aluminium diaphragm is demonstrated and compared with the theoretical model. The results obtained are very promising for future application of ESPSI systems with HOEs, for modal analysis. A significant advantage of shearography over electronic speckle pattern interferometry is that ESPSI is relatively insensitive to external disturbances. Another advantage of the proposed system is that it could be easily converted to a phase-shifting electronic speckle shearing interferometer. 相似文献
4.
An idea of using laser Doppler velocimeter (LDV) to measure the velocity for the vehicle inertial navigation system was put forward. The principle of measuring its own velocity with laser Doppler technique was elaborated and reference-beam LDV was designed. Then Doppler signal was processed by tracking filter, frequency spectrum refinement and frequency spectrum correction algorithm. The result of theory and experiment showed that the reference-beam LDV solved the problem that dual-beam LDV cannot be used for measuring when the system was out of focus. Doppler signal was tracked so that signal-to-noise ratio was improved, and the accuracy of the system was enhanced by the technology of frequency spectrum refinement and correction. The measurement mean error was less than 1.5% in velocity range of 0-30 m/s. 相似文献
5.
Joris Vanherzeele Steve Vanlanduit Patrick Guillaume 《Optics and Lasers in Engineering》2007,45(1):49-56
In the last decade the laser Doppler vibrometer (LDV) has become a widely spread instrument for measuring vibrations. It often offers accurate measurements with a high spatial resolution. However, the measurement time of the LDV and especially for the scanning LDV is long. Therefore, reducing the measurement time is an attractive objective. A way to achieve this is to use a single sine excitation (on a resonance frequency). However, this technique has two major drawbacks: the inability to provide information on the damping and a operational deflection shape that can differ from the true mode shape. In this article two methods will be introduced to reduce measurement time without these defaults. In the first method introduced in this article a narrow band multisine is used as excitation signal and the measured vibration signal in the time domain is represented by a model using sines and cosines with these fixed narrow band frequencies. The coefficients of those sines and cosines are then estimated on a global scale by means of a least-squares estimator. An important advantage of this particular technique is that one does not have to measure a full period of the signal, reducing time. The second method accelerates the measurement time for scanning LDV measurements. Using the time domain sequence from each previous scan point and a limited number of time samples from the current scan point, the full time domain sequence of the current scan point can be estimated. Both these methods are a key benefit for in-line quality control, which can have upwards of 1000 spatial measurement locations. The proposed techniques will be validated on both simulations and experiments of varying complexity. 相似文献
6.
7.
An experimental demonstration of using a single longitudinal mode solid-state laser source in laser Doppler velocimeter (LDV) is presented. The technology of frequency spectrum correction is used in processing Doppler signal. The results of the experiments show that: the magnitude and signal-to-noise ratio (SNR) of Doppler signal are both enhanced by the solid-state laser; the measurement accuracy of LDV is improved by the technology of frequency spectrum correction, and the variance of the measured Doppler frequency is larger than the Cramer-Rao low bound (CRLB) of Doppler frequency about one order of magnitude. 相似文献
8.
Laser Doppler vibrometer (LDV) has a potential application prospect in remote sensing. Based on the correlation theories of heterodyne detection, a LDV system with a configuration of all fiber and heterodyne techniques is developed to detect the sound signal through the vibration of glass. Experimental results show that the LDV system has an ability to acquire the real-time speech signal 25 m away through glass. While, the system signal-to-noise ratio (SNR) value decreases with the increase of the glass thickness and the detection distance. 相似文献
9.
10.
This study provides two non-contact optical techniques to investigate the transverse vibration characteristics of piezoceramic rectangular plates in resonance. These methods, including the amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and laser Doppler vibrometer (LDV), are full-field measurement for AF-ESPI and point-wise displacement measurement for LDV, respectively. The edges of these piezoceramic rectangular plates may either be fixed or free. Both resonant frequencies and mode shapes of vibrating piezoceramic plates can be obtained simultaneously by AF-ESPI. Excellent quality of the interferometric fringe patterns for the mode shapes is obtained. In the LDV system, a built-in dynamic signal analyzer (DSA) composed of DSA software and a plug-in waveform generator board can provide the piezoceramic plates with the swept-sine excitation signal, whose gain at corresponding frequencies is analyzed by the DSA software. The peaks appeared in the frequency response curve are resonant frequencies. In addition to these optical methods, the numerical computation based on the finite element analysis is used to verify the experimental results. Good agreements of the mode shapes and resonant frequencies are obtained for experimental and numerical results. 相似文献
11.
12.
We introduce a heterodyne interferometer scheme utilizing the double-pass arrangement of the deflected beams of an acousto-optic modulator. To prove our new idea, the interferometer has been applied for measuring small amplitude vibrations. The output intermediate frequency signal from the interferometer is processed by using an I/Q demodulator. In theory, it can provide the quantum noise limited sensitivity, whereas, in our present Letter, the sensitivity of the phase measurement is limited by the resolution of the 16?bit A/D converter used for processing the I/Q signals. Details of our interferometer scheme are discussed. 相似文献
13.
微振动振幅的精密测量 总被引:3,自引:1,他引:2
本文给出一种微振动振幅的精密测量方法.此方法采用光拍相位检测、伺服锁定干涉仪光程差和窄带检测技术,大大提高了信噪比.微振动振幅检测灵敏度达2.2×10~(-2)(?)/Hz~(1/2)(2kHz信号). 相似文献
14.
Non-contact detection of laser-generated surface acoustic waves using fiber optic Sagnac interferometer 总被引:1,自引:0,他引:1
A high powered Q-switched Nd:YAG laser was used to excite the surface waves, and an optical fiber sensor was used to detect the out-of-plane displacements due to the propagating waves. This sensor is based on the fiber optic Sagnac interferometer, which has the path-matched configuration and does not require active stabilization. Quadrature phase bias between two interfering laser beams in the Sagnac loop is applied by controlling the birefringence in an optical path using a fiber polarization controller. A stable quadrature phase bias can be confirmed by observing the interferometer output according to the change of phase bias. Additional signal processing is not needed for the detection of ultrasonic waves using the Sagnac interferometer. The performance of the fiber optic Sagnac interferometer was investigated, and laser-generated surface wave signals were detected using this fiber optic sensor. The developed fiber optic sensor configured in this study is very simple and is effective for non-contact detection of ultrasonic waves. 相似文献
15.
A new method based on Hilbert–Huang transform is proposed to analyze the laser Doppler signal with a large acceleration. The Doppler signal is decomposed into several Intrinsic Mode Functions (IMFs) via empirical mode decomposition (EMD). And the Hilbert transform is used to compute the instantaneous frequency. The vehicle velocity parameter is estimated by taking linear fitting on the instantaneous frequency of the relevant IMF. The simulation results show that the HHT-based method is quite useful for the LDV that offers velocity parameter to the vehicle self-contained navigation system when the vehicle moves at a large acceleration. 相似文献
16.
The performances of two Laser Doppler Velocimetry (LDV) systems adapted for measuring the acoustic particle velocities are assessed in enclosed sound field. This assessment is performed by comparing the acoustic velocities measured by means of LDV to reference acoustic velocities estimated from sound pressure measurements. The two LDV systems are based on a single optical bench which delivers an optical signal called Doppler signal. The Doppler signal, which is frequency modulated, is analyzed by means of two signal processing systems, the BSA (Burst Spectrum Analyser from Dantec) on the one hand, and a system specifically developed for the estimation of the acoustic velocity on the other hand. Once the experimental setup has been optimized for minimizing the errors made on the reference velocities, the assessment is performed and shows that both systems can measure the acoustic velocity in enclosed field in two the frequency ranges [0-4 kHz] and [0-2 kHz] respectively for acoustic velocity amplitudes of 10 mm/s and 1 mm/s. 相似文献
17.
《中国光学快报(英文版)》2016,(7)
In this study, an improved phase-shifting diffraction interferometer for measuring the surface topography of a microsphere is developed. A common diode-pumped solid state laser is used as the light source to facilitate apparatus realization, and a new polarized optical arrangement is designed to filter the bias light for phase-shifting control. A pinhole diffraction self-calibration method is proposed to eliminate systematic errors introduced by optical elements. The system has an adjustable signal contrast and is suitable for testing the surface with low reflectivity. Finally, a spherical ruby probe of a coordinate measuring machine is used as an example tested by the new phase-shifting diffraction interferometer system and the WYKO scanning white light interferometer for experimental comparison. The measured region presents consistent overall topography features, and the resulting peak-to-valley value of 84.43 nm and RMS value of 18.41 nm are achieved. The average roughness coincides with the manufacturer's specification value. 相似文献
18.
An interferometer based on using low-coherent light source, a square prism, and the angular-scanning technique is proposed for absolute angular-displacement determinations. An angular displacement of the square prism shifts the correlogram, which is modulated by an envelope function, of the interference signal of the beams passing through the prism. This angle can thus be discovered by detecting the shifting of the envelope peak. A setup constructed to validate the interferometer is used. The results of using this setup are then presented. 相似文献
19.
20.
A frequency-stabilized helium-neon laser with Zeeman frequency splitting in the magnetic field was studied. A series of pulses with repetition frequency equal to the frequency difference caused by the splitting of the gain profile by the magnetic field was used as a reference signal for a laser interferometer. The modulation of discharge current by electric noise or natural oscillations of the discharge current were found to lengthen the edges of these pulses, which decreases the accuracy of measurements with a laser interferometer. 相似文献