Absolute test of flats based on even or odd functions

Aiming at the problem that detection accuracy of plane interferometry is limited by accuracy of reference surface shape, it is proposed to eliminate influence of reference surface error in interference system by using high precision absolute detection method based on parity function. Influences of rotation angle error and rotation eccentricity error on measurement accuracy of absolute detection method are simulated. Experiments and repetitive experiments of absolute detection accuracy are designed and analyzed by commercial Fischer interferometer. Simulation results show that measurement error PV value is 0.000 1λ when rotation angle error reaches 0.13 °; measurement error PV value is 0.005λ when rotation eccentricity error reaches 3 pixels. Experimental results show that absolute detection accuracy of actual sample PV₁₀ value is 0.041 5λ and RMS value is 0.008 7λ, which is smaller than that of conventional interference detection. Point to point processing is done for two independent absolute detection results in the same plane, in this way residual graph is obtained with PV₁₀ value is 0.004 λ and RMS value is 0.000 5 λ. Experimental results show that this method is highly reproducible and effective.