一维相移剪切干涉仪的调制度函数分析

Analysis of Modulation Function in the One-Dimensional Phase Shifting Lateral Shearing Interferometry

为了分析一维相移剪切干涉仪中调制度的变化规律和影响。研究了一维光栅相移剪切干涉仪的基本原理,推导了干涉光强公式和光强调制度函数。通过将泽尼克单项像差代入到调制度函数因子,分析了泽尼克像差、剪切比对调制度函数的影响,发现测量范围主要受到高级球差和大剪切比限制。设计了一维相移剪切干涉仪的可见光实验装置,在632.8 nm波长分别使用周期为9 mm、18 mm一维光栅测量了一个NA=0.25显微物镜的波像差,实验结果表明:光栅周期为18 mm时可以正确测量,光栅周期为9 mm时,调制度存在反转点,像差超出测量范围,并验证调制度函数分析结果的正确性。

In order to analyze the variation rule and influence of the modulation in the one-dimensional phase shifting lateral shearing interferometer （PS LSI）. The principle of the PS LSI based on one-dimensional Ronchi grating is researched. The inference intensity formula and intensity modulation function are reduced. By substituting the each Zernike aberration into the modulation function factor, the influence due to Zernike aberration and shear ratio are analyzed. The measurement range is mainly limited by the high order spherical aberration and large shear ratio. Finally, an experimental setup is designed to measure the wavefront aberration of a NA=0.25 microscope objective at 632.8 nm wavelength, in which using two one-dimensional gratings with 9 μm and 18 μm period respectively. The results show that when grating period is 18 μm, the measurement result is correct; when grating period is 9 μm, the reversed points exist in the modulation, the aberration is beyond the measurement range, and the correctness of the modulation function analysis result is validated.