Improving the accuracy of interferometer testing with absolute surface calibration and power spectral density analysis

A novel absolute surface calibration method for interferometer testing based on power spectral density analysis has been proposed. The method involves obtaining the loss of signal at different frequencies as a function of various rotation angles by signal analysis to choose the rotation angle for calibration. A model is developed to evaluate the calibration method by creating random surface shapes based on the Power Spectral Density. Using this algorithm, the precision of the absolute testing method during the testing process exceeds 0.28 %. Error propagation during the experimental process, such as testing optic clamping, angular errors, eccentricity, vibrations and airflow disturbances, were calibrated. Ultimately, the absolute detection test results were verified using high-precision flat mirrors. The experimental result indicates an RMS of 4.275 nm, 4.263 nm, and 4.265 nm in different rotation angle, and the calibrated result shows an RMS of 4.880 nm. The shape of surface errors in the absolute test results and calibration results is consistent.