Reference surface calibration of a Fizeau interferometer through even/odd synthesis.

We propose an even-/odd-synthesis method for the elimination of additional aberration caused by misalignment or environmental vibration during the calibration of a Fizeau interferometer reference surface (RS). The odd and even parts of an RS can be obtained, because surface errors could be divided into rotationally symmetric and nonrotationally symmetric terms. We then propose a least-squares algorithm with a dual-objective optimization function for calibration of the measurement results at the confocal position. Finally, a complete RS can be eventually obtained by synthesizing the odd and even parts of the RS. It has been verified through experiments that the measurement repeatability of the PV value is better than 0.003λ, and the root-mean-square value is better than 0.0003λ.