Separate the primary aberration for the deformation error of optical flat in 300-mm-aperture vertical Fizeau interferometer

As a key component in a phase-shifting interferometer, the optical flat is often affected by supporting methods and generates deformation. In this paper, we propose a method to separate the deformation error through rotation measurement and Zernike polynomial fitting. We studied the principles, simulations, and experiments of this method. First, a support model is established in Comsol, and the deformation of the optical flat is analyzed. Then, the numerical simulation of the separation method for the deformation is performed, and the corresponding experiment is carried out on a 0300 mm vertical Fizeau interferometer to verify the correctness of the method. The results show that numerical calculation and experimental measurement results are in good agreement, the difference between the PV value and the RMS value are only 0.004 lambda and 0.002 lambda, respectively. Finally, the error term that affected the calculation accuracy was analyzed. This proves that the proposed method can effectively separate the deformation introduced by the support.