Analysis of measurement error for the absolute testing of flat

Absolute measurement is based on the Fizeau interferometer system, which features a common optical path that mitigates the impact of system-specific errors and is less sensitive to environmental changes. Currently, methods for flat absolute measurement include: the three-plate mutual inspection method, the odd-even function method, the rotational symmetry method, and the mirror symmetry method, etc. Typically, the odd-even function method is used for flat absolute measurement, but it is commonly used and has proven effective for circular domain boundary conditions in existing absolute surface measurements. To measure and fit rectangular domain boundary conditions, this paper also utilizes Zernike polynomials and Chebyshev polynomials to fit rectangular domains, with Schmidt orthogonalization used to achieve Zernike fitting for rectangular domains, and their performance is compared.