A novel on-axis self-calibration approach for precision rotary metrology stages

Precision rotary metrology stages need calibration technology to determine the stage error for improvement of angle measurement accuracy. In this paper, we study the calibration of precision rotary metrology stages, and present an on-axis angle self-calibration approach different from previous perspectives. Without resorting to specially designed angle comparators or added read-heads, the proposed scheme fully utilizes different measurement views of a newly designed artifact plate on the uncalibrated rotary stage. The measurement deviation of each mark line from its nominal angle position, is rigidly modeled as the combination of stage error, artifact error, misalignment error and random measurement noise. Based on the circle closure principle and mathematical definition of the axis orientation, the misalignment error of each measurement view can be directly determined by rigid algebraic processing. A least-square based calculation law is finally synthesized to determine the stage error. Computer simulation validates that the proposed method can realize the stage error accurately even there exist various random measurement noises. Finally, a practical description on how to measure the angular marks of different measurement views is provided. The proposed strategy essentially provides a novel on-axis angle self-calibration principle with accuracy, simplicity and robustness orientation to meet industrial requirements.