Dynamic calibration of the air-bearing table for the swing arm profilometer test

The swing arm profilometer (SAP) has great potential to achieve high-accuracy measurements for large-aperture optic surfaces. To promote the precision of the SAP further, we proposed a dynamic calibration setup with four high-accuracy capacitive probes and a standard circular ring flat to monitor error motions of the air-bearing table of the SAP during surface measurement. We implemented an experiment on a ∅400 mm flat and achieved an accuracy of 15 nm. Compared with the traditional SAP test results, the accuracy was improved by 25%. Experimenting on a ∅2000 mm off-axis aspheric surface displayed that the ring-shaped system errors from the SAP test were eliminated with a 12% improvement in accuracy. It exhibited a good suppression effect on rotationally symmetric errors from the SAP.