Absolute flat test by a coherent shift-rotation method with yaw-angle monitoring

Area of Science:

• Metrology
• Optical Engineering
• Surface Metrology

Background:

• Accurate absolute measurement of flat surfaces is crucial in various scientific and industrial applications.
• Existing methods often involve complex setups or redundant procedures.

Purpose of the Study:

• To propose and validate a novel coherent shift-rotation method with yaw-angle monitoring (CSR-YAM) for absolute surface measurement.
• To develop a surface reconstruction system capable of pixel-level accuracy without theoretical error.

Main Methods:

• The CSR-YAM method utilizes a simple configuration with a single auxiliary mirror for yaw-angle monitoring.
• Shift-rotation difference maps and relative yaw angles are used for surface reconstruction.
• An efficient iterative solver is employed for high-dimensional surface recovery.

Main Results:

• Simulations confirm the high accuracy, efficiency, and robustness of the CSR-YAM method.
• Experimental results demonstrate excellent agreement with direct measurements using a sub-nanometer RMS transmission flat.

Conclusions:

• The CSR-YAM method offers a simplified and accurate approach for absolute flat surface metrology.
• The developed system achieves pixel-level surface recovery with high precision and efficiency.