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散斑在轴向的退相关现象是制约散斑干涉测量适用性的关键问题之一,为了提高散斑场的纵向相关性,从而提高散斑干涉图像的条纹对比度,扩大物体离面形变的测量范围,提出一种对散斑场进行相位编码调制的方法,即将波前编码技术扩展景深的方法用于散斑场编码,在孔径光阑位置上放置立方型相位板实现相位调制。首先分析了该编码调制方法用于提高散斑场纵向相关性的可行性,然后基于4f系统模拟仿真并实验验证了通过相位编码调制提高编码散斑场的纵向相关性的实际效果。结果表明,编码后散斑的纵向尺寸从0.17 mm提高到0.4 mm,大约提高了2.5倍。
In order to improve the vertical correlation of speckle field and improve the fringe contrast of speckle interference images and to expand the measurement of out-of-plane deformation of objects, the backscattering phenomenon of speckle is one of the key problems that restrict the applicability of speckle interferometry. This paper proposes a method of phase modulation modulation of speckle field by using wavefront coding method to expand the depth of field for speckle field coding and placing cubic phase plate on the position of aperture stop for phase modulation. Firstly, the feasibility of using this code modulation method to improve the longitudinal correlation of speckle fields is analyzed. Then the simulation results based on 4f system simulation and experimental results verify the practical effect of improving the vertical correlation of the encoded speckle field by phase modulation modulation. The results showed that the longitudinal speckle speckle increased from 0.17 mm to 0.4 mm, an increase of about 2.5 times.