数字全息干涉位移场分离研究

Study on separation of displacement field in digital holographic interferometry

提出了一种基于窗口傅里叶脊的离面与面内位移分离方法,应用于数字全息的多分量干涉相位场分离。首先,物光束对称照射待测物体,参考光束直接照射CCD靶面,由CCD相机记录物体变形前后的两幅离轴数字全息图;然后,采用菲涅尔衍射积分法再现物体变形前后的复物光场,再由两幅复物光场共轭相乘构建干涉场,利用幅度区分准则和窗口傅里叶变换处理复干涉场,通过窗口傅里叶脊值的搜索,提取不同灵敏度矢量物光对应的干涉相位分量;再对干涉相位场进行简单数值运算,将面内与离面位移场分离出来。最后,对周边固定、点加载、绕轴向旋转的Al制圆盘三维位移场进行实际测量。实验结果验证了本文方法的有效性。

A novel method based on windowed Fourier ridge for separation of out-of-plane displacement from ircplane displacement is presented and applied to the separation of multiple interference phases in digital holographic interferometry. Firstly,a single laser light source is used to illuminate the tested object symmetrically to its surface normal,and a single reference beam is used in conjunction with the dif- fusely scattered object beams to record the hologram at the CCD plane. Two frames of off-axis hologram before and after object deformation are captured by CCD. Then, Fresnel diffraction integral reconstruction provides two complex object wave-fields before and after object deformation, and the interference field can be obtained by the conjugate mutiplication of two frame reconstructed complex object wave- fields. Windowed Fourier ridge and amplitude discrimination criteria are allowed to separate multiple in- terference phases which carry the information on multidimensional deformation corresponding to the ob- ject beams with different sensitivity directions. Out-of-plane displacement can be separated from in-plane displacement only by simple numerical calculation of multiple interference phases. Finally, the experiment is conducted to prove the validity of the proposed method. A fully-clamped circular aluminum disk with a point load and in-plane rotation along its normal is chosen as a specimen,and its three-dimensioal （3D） displacements are successfully measured by the proposed method. The feasibility of proposed algorithm is demonstrated by the experimental results.