Measuring the indication error of the Fizeau interferometer and evaluating its uncertainty

The indication error, as a characteristic of the interferometer, can be obtained through verification and calibration, and the uncertainty during measurement represents the reliability of the indication error. This paper employed the modified absolute measurement method to gain the indication error. First, the improved absolute algorithm was derived. Then, the absolute measurements were conducted with a 150-mm-aperture Fizeau interferometer. The measured indication error conforms to the maximum allowable error of the interferometer. Finally, the measurement uncertainty evaluation was carried out based on the method to characterize the indication error’s dependability, which was much less than one-third of the maximum allowable error.