Pose-varied swing arm profilometer test for off-axis aspheric surfaces with strong asphericity

The swing arm profilometer (SAP) has been widely used to test large aspheric optics by measuring the asphericity from its best-fitting sphere (BFS). To further improve the test accuracy, we propose a pose-varied test mode for the SAP with a shorter-range probe to measure off-axis aspheric surfaces with stronger asphericity. In contrast to the classical SAP mode in which the air-table is fixed in a stationary position during measurement, we adjust the pose of each scan arc to match the local BFS and the measurement range of the probe decreases to half that of the global asphericity. To verify the effectiveness, we conduct experiments on an off-axis asphere with a diameter of 3 and 2 m. Compared with a classical SAP mode, it achieved an improved performance of 50% higher repeatability and 32% higher accuracy. (C) 2021 Optical Society of America

Automated summary

To improve the accuracy of testing large aspheric optics, a pose-varied test mode for the swing arm profilometer (SAP) was proposed, adjusting the pose of each scan arc to match the local best-fitting sphere for measuring off-axis aspheric surfaces with stronger asphericity. Experimental results showed a 50% increase in repeatability and a 32% increase in accuracy compared to the classical SAP mode.