Absolute interferometric shift-rotation method with pixel-level spatial frequency resolution

• A pixel-level spatial frequency solution of shift-rotation method is presented.
• No orthogonal polynomials fit and interpolations are required in the calculation.
• Only four measurements are required in the method.
• Simulations and experimental absolute results of flat surfaces are given.
• Estimation of uncertainty is given.

Absolute interferometric testing method of shift-rotation in a Fizeau interferometer is effective in optical surface metrology with high accuracy and has been developed for decades. A pixel-level spatial frequency solution of interferometric shift-rotation method is presented in the manuscript. It requires a 90° rotational measurement and at least two translational measurements with different translations in the x and y directions besides a measurement at an original confocal position (0°). With the well-organized absolute procedures, the absolute surface deviation of the test and reference surface can be obtained accurately with pixel-level spatial frequency resolution. As a result, the absolute results of the method contain much more mid-to high spatial frequency information and it is useful to directly detect the defects (dusts, pits) of the test and reference surfaces. No orthogonal polynomials fitting (such as Zernike polynomials) and interpolations are required in the calculation, and the absolute results can be guaranteed with high accuracy. Experimental absolute results of flat surfaces are given.