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.