高速流场激光干涉检测相位信息的提取与分析

发布时间：2018-03-11 20:02

本文选题：小波变换　切入点：提取相位　出处：《烟台大学》2017年硕士论文　论文类型：学位论文

【摘要】：在高速流场测量等领域,常用干涉法得到条纹图,通过提取干涉条纹的相位进而得到所需待测信息,因此研究干涉条纹图相位的提取具有非常重要的意义。本文主要研究了高速流场中干涉条纹图相位的提取,主要内容包括以下几个方面:(1)介绍了几种目前常用的提取干涉条纹图相位的方法,主要有相移法、傅里叶变换法和时频分析法,其中,时频分析法中介绍了加窗傅里叶变换法和小波变换法。介绍了每一种算法的优点,同时总结出相移法、傅里叶变换法及加窗傅里叶变换法提取干涉条纹相位的局限性,最后提出本文所用的二维连续小波变换法。(2)二维连续小波变换具有灵活的时频分析窗,可以实现对信号的多尺度细化分析。为了解决传统二维连续小波变换耗时时间长的问题,将传统二维连续小波变换算法进行改进,提出将传统二维连续小波变换中连续的尺度因子和旋转角用少量的离散尺度因子和旋转角代替,这样就大大降低了处理的时间。在计算小波系数的过程中,由于存在卷积计算而使得计算仍然很耗时,引入了快速傅里叶变换,从而进一步降低处理的时间。在计算得到小波系数后,通过脊检测算法找出小波脊,进而得到干涉条纹相位。(3)利用传统二维连续小波变换法和本文改进的二维连续小波变换法首先对计算机仿真干涉条纹图及实验得到的干涉条纹图进行相位提取与分析,然后再利用这两种算法对高速流场中几组不同的干涉条纹图进行相位提取,在提取相位之前,对干涉条纹图进行中值滤波、同态滤波及二值化的预处理过程,然后利用传统二维连续小波变换法和本文改进的二维连续小波变换法分别对干涉条纹图进行相位提取,通过比较干涉条纹图在这两种算法下处理前后的峰值信噪比PSNR和均方根误差RMSE可以得到在准确性基本保持不变的情况下,本文改进的二维连续小波变换法是可以准确提取出干涉条纹图相位的。同时,根据本文提出的覆盖图的方法,大大减少了传统二维连续小波变换法计算过程中参数对的数量,加快了处理时间。分析结果表明,本文改进的二维连续小波变换算法可以快速准确的提取出干涉条纹图的相位,对于提取高速流场中干涉条纹图的相位具有一定的可行性。
[Abstract]:In the field of high speed flow field measurement, the fringes are obtained by interferometry, and the information to be measured is obtained by extracting the phase of interference fringes. Therefore, it is very important to study the phase extraction of interference fringes. In this paper, the phase extraction of interference fringes in high velocity flow is studied. The main contents include the following aspects: 1) this paper introduces several commonly used methods for extracting the phase of interference fringes, such as phase-shift method, Fourier transform method and time-frequency analysis method. In time-frequency analysis, the windowed Fourier transform method and wavelet transform method are introduced. The advantages of each algorithm are introduced. At the same time, the limitation of phase shift method, Fourier transform method and windowed Fourier transform method for extracting interference fringe phase is summarized. Finally, the two-dimensional continuous wavelet transform is presented in this paper. The two-dimensional continuous wavelet transform has a flexible time-frequency analysis window, which can realize the multi-scale thinning analysis of the signal. In order to solve the problem of the traditional two-dimensional continuous wavelet transform, it takes a long time. The traditional two-dimensional continuous wavelet transform algorithm is improved, and the continuous scale factor and rotation angle in the traditional two-dimensional continuous wavelet transform are replaced by a small amount of discrete scale factor and rotation angle. In this way, the processing time is greatly reduced. In the process of calculating wavelet coefficients, the computation is still time-consuming due to the existence of convolution calculation, and the fast Fourier transform is introduced. In order to further reduce the processing time. After the wavelet coefficients are calculated, the wavelet ridges are found by ridge detection algorithm. Then the phase of interference fringes is obtained. The traditional two-dimensional continuous wavelet transform method and the improved two-dimensional continuous wavelet transform method are used to extract and analyze the phase of the computer simulation interference fringe image and the experimental interference fringe image. Then the two algorithms are used to extract the phase of several different interference fringes in the high-speed flow field. Before the phase extraction, the median filtering, homomorphic filtering and binary preprocessing of the interference fringes are carried out. Then the traditional two-dimensional continuous wavelet transform method and the improved two-dimensional continuous wavelet transform method are used to extract the phase of interference fringes. By comparing the peak signal-to-noise ratio (PSNR) and root mean square error (RMSE) of interferometric fringe images before and after processing under these two algorithms, we can get that the accuracy is basically unchanged. The improved two-dimensional continuous wavelet transform method can accurately extract the phase of interference fringes. At the same time, the number of parameter pairs in the calculation process of traditional two-dimensional continuous wavelet transform method is greatly reduced according to the method of covering image proposed in this paper. The analysis results show that the improved two-dimensional continuous wavelet transform algorithm can extract the phase of interference fringes quickly and accurately, and it is feasible to extract the phase of interference fringes in high-speed flow field.
【学位授予单位】：烟台大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O436.1

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