为了在共光路的干涉仪上实现同步移相,达到干涉测量抗震的目的,设计了一种新的同步移相抗震方案并搭建了实验装置。通过改变半导体激光器的注入电流,改变其相干长度,作为短相干光源,利用光源的相干性,结合偏振延迟装置,分开了参考光和测试光形成一对正交偏振光。同步移相系统由二维正交光栅和偏振片组构成,两个±1级衍射光通过透振方向依次相差45°的偏振片组合,在一个CCD上同时得到4幅互有90°相移的移相干涉图。按照传统的四步法,复原待测波面。测试了一个平行平板样品,结果PV为0.068 λ,RMS为0.013 λ(λ=650 nm)。同一被测件用Zygo干涉仪测量结果PV为0.063 λ,RMS为0.012 λ(λ=632.8 nm),两者符合较好。

An on-axis,vibration insensitive,polarization Fizeau interferential system is built. In this arrangement,a multimode semiconductor laser is used as the light source,of which coherence in conjunction with a polarization delay-line is used to effectively separate out the orthogonally polarized test and reference beam components for interference. Spatial phase-shifting system is realized by a 2D grating and a polarizer group. The four ties of rays including two ±1 diffraction rays with the same intensity are projected through four polarizers,of which the axis directions are 0°,45°,90°,135°,and four π/4 phase shifting interferograms are received by one CCD simultaneously. By using the 4-bucket algorithm,wavefront to be tested is recovered. Flatness of a parallel plate surface is measured by this system with PV of 0.068 λ,RMS of 0.013 λ (λ=650 nm) and by Zygo interferometer with PV of 0.063 λ,RMS of 0.012 λ(λ =632.8 nm). The two results obtained are in close agreement.