移相器类进动现象对干涉测量的影响

Effect of Phase Shifter′s Sub-Processional Motion on Interferometry

压电晶体 (PZT)光学移相器作为移相干涉仪 (PSI)的关键部件 ,其移相误差直接影响被测波面的相位复原精度。分析了压电晶体移相器在移相过程中导致干涉图旋转的原因———类进动 ,其本质是移相器在伸长的同时其参考镜端面法线方向绕着伸长方向产生旋转。利用典型的Hariharan五步移相算法 ,得出了类进动现象所导致的波面相位复原误差计算公式 ,给出了在测试孔径上的误差分布图。对影响误差大小的主要因素如干涉条纹的宽度、旋转的角度和测试口径等进行了具体分析 ,由此推导出在移相干涉仪光学调整过程中控制干涉图旋转误差的准则。

In modern digital phase-shifting interferometry (PSI), the phase-shifting error of piezoelectric transducer (PZT) optical phase shifter, which is the basic device of phase-shifting interferometer, directly effects measurement accuracy during wavefront phase unwrapping with phase-shifting interferograms. A phenomenon named sub-processional motion that can result in fringes′ rotation in the processing of phase shift is described. This phenomenon is derived from the normal-line rotation of standard reference surface revolving around the elongate direction of PZT phase shifter. In terms of the classic phase-shifting algorithm-Hariharan 5-Bucket algorithm, the error formula of phase unwrapping is given due to sub-processional motion, and the error distribution on aperture is also derived. Based on error factor analysis, criterions to control the error are presented at such aspects: width of fringes, rotation angle and tested aperture.