Liu Ke, Li Yanqiu, Wang Hai
Key Laboratory of Photoelectronic Imaging Technology and System, Ministry of Education of China, School of Optoelectronics, Beijing Institute of Technology, Beijing 100081, China.
Rev Sci Instrum. 2011 Mar;82(3):033105. doi: 10.1063/1.3560072.
Characterization of measurement accuracy of the phase-shifting point diffraction interferometer (PS∕PDI) is usually performed by two-pinhole null test. In this procedure, the geometrical coma and detector tilt astigmatism systematic errors are almost one or two magnitude higher than the desired accuracy of PS∕PDI. These errors must be accurately removed from the null test result to achieve high accuracy. Published calibration methods, which can remove the geometrical coma error successfully, have some limitations in calibrating the astigmatism error. In this paper, we propose a method to simultaneously calibrate the geometrical coma and detector tilt astigmatism errors in PS∕PDI null test. Based on the measurement results obtained from two pinhole pairs in orthogonal directions, the method utilizes the orthogonal and rotational symmetry properties of Zernike polynomials over unit circle to calculate the systematic errors introduced in null test of PS∕PDI. The experiment using PS∕PDI operated at visible light is performed to verify the method. The results show that the method is effective in isolating the systematic errors of PS∕PDI and the measurement accuracy of the calibrated PS∕PDI is 0.0088λ rms (λ = 632.8 nm).
相移点衍射干涉仪（PS∕PDI）测量精度的表征通常通过双针孔零位测试来进行。在此过程中，几何彗差和探测器倾斜像散系统误差比PS∕PDI所需的精度高近一两个数量级。必须从零位测试结果中准确消除这些误差，以实现高精度。已发表的校准方法虽然能够成功消除几何彗差误差，但在校准像散误差方面存在一些局限性。在本文中，我们提出了一种在PS∕PDI零位测试中同时校准几何彗差和探测器倾斜像散误差的方法。该方法基于从两个正交方向的针孔对获得的测量结果，利用泽尼克多项式在单位圆上的正交和旋转对称特性，计算PS∕PDI零位测试中引入的系统误差。进行了使用可见光下运行的PS∕PDI的实验来验证该方法。结果表明，该方法能够有效分离PS∕PDI的系统误差，校准后的PS∕PDI测量精度为0.0088λ 均方根（λ = 632.8 nm）。
