On-axis self-calibration of precision XYθz metrology systems: An approach framework

As previous self-calibration technologies are mostly limited to X, XY, XYZ, and angular metrology stages, we study the self-calibration of precision XYθ_z metrology stages and present an on-axis self-calibration strategy. Specifically, a designed artifact plate with grid mark lines and angular mark lines whose accuracy is not precisely known, is presented as the assistant tool. And four measurement views of the designed artifact plate on the uncalibrated XYθ_z stage are fully utilized to provide the symmetry, transitivity and redundance of the XYθ_z systematic measurement error (i.e., stage error). In addition, circle closure principle is employed for the angular stage error component. Resultantly, a least-square based calculation law is proposed for the final determination of the stage error. Computer simulation is conducted and the calculation results validate that the proposed scheme can accurately realize the stage error even under the existence of various random measurement noises. As an integration of XY self-calibration and angular self-calibration, the proposed scheme solve the XYθ_z self-calibration problem, and possesses special merits such as simplifying the mathematical processing for calculation of misalignment errors.