本文選題：光學干涉檢測　切入點：相位測量　出處：《廣東工業(yè)大學》2016年博士論文　論文類型：學位論文

【摘要】：激光波數(shù)掃描干涉技術通過透視測量復合材料內部的應變場,實現(xiàn)復合材料高精度無損透視檢測,測量精度達到微應變級別,這是目前微米級缺陷無損檢測的重要手段之一。然而受激光器波數(shù)輸出范圍有限影響,激光波數(shù)掃描干涉的深度z方向測量精度和輪廓分辨率均遠遜色于傳統(tǒng)的光學層析相干技術,并且復合材料內部介質的先驗知識無法獲取,導致不能有效分離出材料內部的干涉信號。另外,由于復合材料內部介質的反射光強過弱,造成內部干涉光強信號淹沒于散斑噪聲中。上述問題使得激光波數(shù)掃描干涉技術的實際檢測效果遠達不到理想要求。為解決上述問題,本論文提出在不增加激光波數(shù)掃描范圍前提下,使用非線性最小二乘理論和空間譜估計理論提高激光波數(shù)掃描干涉的深度z方向測量精度和輪廓分辨率,并實現(xiàn)多表面干涉信號的盲分離,完成材料內部干涉信號的提取。同時,論文研究了基于非線性最小二乘理論的散斑噪聲去除問題,提升了信噪比。論文主要研究內容和取得的成果如下：(1)使用復數(shù)域、實數(shù)域非線性最小二乘理論分別對干涉頻譜和波數(shù)域干涉光強進行非線性擬合,分別建立了干涉頻譜非線性最小二乘算法(Complex Number Least Squares Algorithm, CNLSA)和波數(shù)域干涉光強非線性最小二乘算法(Wavenumber-domain Least Squares Algorithm, WLSA)。CNLSA和WLSA可以去除傅里葉變換中的窗函數(shù)卷積模糊效應,取代傅里葉變換算法完成對激光波數(shù)掃描干涉數(shù)據(jù)的解調。實驗結果表明在相同實驗環(huán)境條件下,CNLSA和WLSA將測量系統(tǒng)深度輪廓分辨率由原來的δz分別提升到δz/1.8和δz/6。與此同時,相位測量精度因旁瓣壓制能力增強而提高。(2)通過結合空間譜估計理論和相移干涉技術的數(shù)據(jù)解調原理,建立干涉信號相關矩陣譜分解及復數(shù)線性最小二乘理論(Eigenvalue Decomposition and Least Squares Algorithm, EDLSA),具體表現(xiàn)在：以空間譜估計理論為基礎,通過深度分辨干涉信號自相關矩陣的譜分解,實現(xiàn)被測表面?zhèn)�數(shù)的盲估計；使用旋轉不變技術求解干涉信號頻率；在干涉頻率已知情況下,將相移干涉技術中的實數(shù)域線性最小二乘算法發(fā)展到復數(shù)域,求解出干涉信號相位和干涉幅值,最終實現(xiàn)了激光波數(shù)掃描干涉信號的盲分離。實驗結果表明EDLSA在激光波數(shù)掃描較窄的情況下,仍然可以根據(jù)CCD相機采集的光強值準確地盲分離出多表面干涉信號,且深度z方向測量精度和輪廓分辨率好于傅里葉變換算法。(3)在不破壞干涉顯微x,y空間分辨率前提下,提出使用干涉頻譜非線性最小二乘-傅里葉變換算法(Joint Fourier Transform and Complex Number Least Squares Algorithm, JFTLSA)對深度分辨散斑噪聲進行降噪。具體表現(xiàn)為：充分利用深度z方向上的被測各個表面之間干涉信號幅值、頻率以及相位耦合關系,改進干涉頻譜非線性最小二乘方法,使非線性最小二乘待估參數(shù)維度顯著降低,提高其在散斑噪聲下的收斂性；針對空間卷繞相位建立噪聲點定位方程,結合傅里葉變換算法,修正改進干涉頻譜非線性最小二乘的卷繞相位發(fā)散點。深度分辨散斑干涉實驗結果表明相比于傅里葉變換算法,JFTLSA可以使散斑噪聲點數(shù)減少約20%左右。
[Abstract]:Laser scanning interferometry by wavenumber strain field measurement perspective composite materials, composite materials to achieve high precision nondestructive X-ray detection, the measurement accuracy of the micro level, this is one of the important means of the current micro defect nondestructive testing. However the laser output range of wavenumber limited effect, optical tomography laser scanning interferometry Z depth direction wavenumber the measurement accuracy and resolution are far inferior to the outline of the traditional coherent technology, and internal medium composite prior knowledge cannot be obtained, so it can not effectively isolate the interference signal inside the material. In addition, due to the internal reflection intensity of composite media is too weak, resulting in internal interference signals submerged in the speckle noise. Because of these problems laser scanning interferometry detection effect of actual wave number is not up to the ideal requirements. To solve the above problems, this paper proposed in Laser scanning range of wave number does not increase under the premise of using nonlinear least squares theory and spatial spectrum estimation to improve the laser scanning interference depth z wavenumber direction measurement precision and contour resolution theory, and realize blind separation of multiple surface interference signals, extract material internal interference signal. At the same time, the problem of removal of speckle noise in nonlinear least squares based on the theory, to enhance the signal-to-noise ratio. The main research contents and achievements are as follows: (1) the use of complex domain, real valued nonlinear least square theory of interference spectrum and frequency domain interference intensity were established by nonlinear fitting, interference spectrum of nonlinear least square algorithm (Complex Number Least Squares Algorithm, CNLSA) nonlinear intensity the least squares algorithm and wavenumber domain interference (Wavenumber-domain Least Squares Algorithm, WLSA.CNLSA and WLSA) You can remove the window function convolution Fu Liye transform fuzzy effect, replacing Fu Liye transform of laser scanning wave interferometric data demodulation. The experimental results show that under the same experimental conditions, CNLSA and WLSA measurement system of depth profile resolution from the original Z respectively to the delta delta z/1.8 and delta z/6. at the same time, improve the accuracy of phase measurement because the sidelobe suppression ability. (2) by combining the spatial spectrum estimation theory and the principle of phase shift interferometry data demodulation, establish interference signal correlation matrix spectral decomposition and plural linear least squares theory (Eigenvalue Decomposition and Least Squares Algorithm, EDLSA), specific performance in: spectrum estimation based on the theory of space, through the depth of resolution spectrum decomposition interference signal autocorrelation matrix, the measured surface number of blind estimation; rotational invariance techniques for solving interference channel use No interference in frequency; frequency is known, phase shift interferometry in real domain linear least squares algorithm to the complex domain, solving the interference signal phase and amplitude of the interference, finally realize the blind separation of laser scanning wave interference signal. Experimental results show that the EDLSA laser scanning in wavenumber narrow circumstances, can still be accurate to the blind separation of multiple surface interference signal acquisition CCD camera according to the intensity value and depth of Z direction measurement precision and contour resolution better than Fourier transform algorithm. (3) without damaging the interference microscope X, y spatial resolution under the premise of using the proposed nonlinear least squares spectrum Fourier transform algorithm (Joint Fourier Transform and Complex Number Least Squares Algorithm, JFTLSA) of depth resolution denoising speckle noise. The specific performance: make use of all the measured depth in the Z direction The surface between the interference signal amplitude, frequency and phase coupling relationship, improved spectrum nonlinear least square method, the nonlinear least squares estimated parameter dimension decreased significantly, improve the convergence of the scattered speckle noise; to establish a phase winding space noise equation, Fourier transform algorithm, a modified phase winding divergence point interference spectrum the nonlinear least squares. Depth resolution speckle interference test results show that compared to the Fourier transform algorithm, JFTLSA can make the speckle noise is reduced by about 20% points or so.

【學位授予單位】：廣東工業(yè)大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TN249

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