双波长剪切散斑干涉法在复合材料缺陷检测中的应用
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摘要
为使剪切散斑干涉能适用于物体大变形的测量,选用双波长激光照射和彩色相机,用傅里叶变换法对干涉图进行频谱分离,用红色波长相位减去绿色波长相位,得到合成波长相位,经频域滤波和相位解包裹,得到连续相位.理论计算表明合成波长相位条纹数是单波长相位条纹数的0.189倍.合成波长参与计算可以有效减小相位条纹密度,解决剪切散斑干涉在物体离面位移测量中由于变形条纹过于密集而导致欠采样的问题,同时降低对干涉条纹滤波和相位解包裹难度,增强图像处理可靠度,提高了测量准确度.给出了合成波长与单波长相位幅度的比较以及相同外力下二者相位条纹密度的对比,实验验证了所提方法的有效性、准确性和可靠性,实现了剪切散斑干涉对复合材料大变形的测量,扩展了剪切散斑干涉工程应用的范围,为新型剪切散斑干涉测量系统的设计提供了参考.
A color CCD camera are adopted to make sure shearography can be applied in large deformation of objects dual-wavelength lasers illumination.By separating the spectrum in the Fourier domain,the subtraction of the red wavelength phase and the green wavelength phase yielded a new phase distribution of a synthetic wavelength.After filtering in frequency domain and phase unwrapping,the continuous phase can be gotten.The number of phase stripes of synthetic wavelength is 0.189 times smaller than that of single wavelength by theoretical derivation.Using the synthetic wavelength can reduce the phase fringe density effectively,and solve the sub-Nyquist sampling problem,which are caused by too intensive interference fringes in object′s deformation.In addition,it also reduces the difficulty of image processing in filtering and phase unwrapping,enhances the reliability of image processing,and improves the measurement accuracy.Phase comparing between synthetic wavelength and single wavelength were given.Moreover,the fringe densities of the two kinds of wavelengths at the same external force also were compared.Experiments verify the effective,accuracy,and reliable of this method.It can process the large deformation measurement of composite material and dramatically expand the measurement rang of shearography in engineering application.It also provides a reference for the designing new type system of shearography.
A color CCD camera are adopted to make sure shearography can be applied in large deformation of objects dual-wavelength lasers illumination.By separating the spectrum in the Fourier domain,the subtraction of the red wavelength phase and the green wavelength phase yielded a new phase distribution of a synthetic wavelength.After filtering in frequency domain and phase unwrapping,the continuous phase can be gotten.The number of phase stripes of synthetic wavelength is 0.189 times smaller than that of single wavelength by theoretical derivation.Using the synthetic wavelength can reduce the phase fringe density effectively,and solve the sub-Nyquist sampling problem,which are caused by too intensive interference fringes in object′s deformation.In addition,it also reduces the difficulty of image processing in filtering and phase unwrapping,enhances the reliability of image processing,and improves the measurement accuracy.Phase comparing between synthetic wavelength and single wavelength were given.Moreover,the fringe densities of the two kinds of wavelengths at the same external force also were compared.Experiments verify the effective,accuracy,and reliable of this method.It can process the large deformation measurement of composite material and dramatically expand the measurement rang of shearography in engineering application.It also provides a reference for the designing new type system of shearography.
引文
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[2]WANG Jin-jiang,WU Ming-yun,LIU Yang.Phase unwrpping algorithm based on graph cuts[J].Acta Photonica Sinica,2012,41(9):1130-1134.王晋疆,吴明云,刘阳.基于图切割的相位展开[J].光子学报,2012,41(9):1130-1134.
[3]SUN Liu-xing,YU Ying-jie,ZHOU Wen-jing.Transient 3D deformation measurement method with color splitting based on ESPI[J].Chinese Journal of Scientific Instrument,2014,35(3):656-662.孙流星,于瀛洁,周文静.颜色分光电子散斑干涉瞬态三维变形测量方法[J].仪器仪表学报,2014,35(3):656-662.
[4]HE Xu,MA Jun.Design of common path radial shearing interferometer[J].Optics and Precision Engineering,2011,19(9):2029-2034.何煦,马军.共光路径向剪切干涉仪的设计[J].光学精密工程,2011,19(9):2029-2034.
[5]HUNG Y Y,TAYLOR C E.Speckle-shearing interferometric camera:a tool for measurement of derivatives of surfacedisplacement[C].SPIE,1973,41:169-175.
[6]HUNG Y Y:Shearography:a new optical method for strain measurement and nondestructive testing[J].Optical Engineering,1982,21(3):391-395.
[7]BLAIN P,PIRON P,RENOTTE Y,et al.An in-line shearography setup based on circular polarization gratings[J].Optics and Lasers in Engineering,2013,51(9):1053-1059.
[8]GAO Yue,FU Shi-hua,CAI Yu-long,et al.Digital shearography investigation on the out-plane deformation of the Portevin-Le Chatelier bands[J].Acta Physica Sinica,2014,63(6):066201-1-5.高越,符师桦,蔡玉龙,等.数字剪切散斑干涉法研究铝合金中Portevin-Le Chatelier带的离面变形行为[J].物理学报,2014,63(6):066201-1-5.
[9]HUNG Y Y,CHEN Y S,NG S P,et al.Review and comparison of shearography and active shearography for nondestructive evaluation[J].Materials Science and Engineering,2009,64:73-112.
[10]FU Y,PEDRINI G,HENNELLY B M,et al.Dualwavelength image-plane digital holography for dynamic measurement[J].Optics and Lasers in Engineering,2009,47(5):552-557.
[11]BHADURI B,TAY C J,QUAN C,et al.Two wavelength simultaneous DSPI and DSP for 3D displacement field measurements[J].Optics Communications,2011,284(10):2437-2440.
[12]LIN Zhen-heng.A method to extract carrier-wave speckle pattern fringe skeletons based on modulation direction[J].Acta Photonica Sinica,2012,41(7):800-804.林振衡.基于调制方向提取载波散斑条纹中心线的方法[J].光子学报,2012,41(7):800-804.
[13]GAO Jian-yong,WANG Kai-fu.Study and design of exponential and butterworth low-pass filters used for digital speckle interference fringe filtering[J].Optik,2013,124(24):6713-6717.
[14]ZHANG Xiong,QIAN Xiao-fan.An improvement on the least-squares phase unwrapping algorithm for under sampled interferogram[J].Acta Photonica Sinica,2011,40(1):121-124.张雄,钱晓凡.欠采样干涉图最小二乘相位解包裹算法改进[J].光子学报,2011,40(1):121-124.
[15]TAY C J,QUAN C,NIU H,et al.Phase retrieval in twowavelength DSSI using a combined filtering method[J].Optik,2011,122(23):2114-2118.
[16]NIU H,QUAN C,TAY C J,et al.Phase retrieval in DSSI for relatively large deformation[J].Optics Communications,2011,284(1):118-122.
[17]GRYZAGORIDS J.Laser based nondestructive inspection techniques[J].Journal of Nondestructive Evaluation,2012,31(4):295-302.
[18]LOBANOV L M,BYCHKOV S A,PIVTORAK V A,et al.On-line monitoring of the quality of elements of aircraft structures by the method of electron shearography[J].Materials Science,2009,45(3):366-371.