Automated Reference Error Subtraction in Phase-Shifting Interferometry

03/10/2026

Automated Reference Error Subtraction in Phase-Shifting Interferometry

Abstract

Phase-shifting interferometry is the gold standard for precision surface and wavefront metrology, but it is fundamentally a comparative measurement. The resultant phase map is a measurement of the optical path difference (OPD) between the test and reference wavefront of the instrument across the field of view. The measured OPD includes any surface form irregularities from the reference surface, directly contributing to measurement error. For valid estimation of OPD, the total error contribution must be adequately small when compared to intended test wavefront. Existing methods to mitigate this error include polishing the reference surface to a high degree of accuracy or performing in-situ calibrations, which can be costly, time-consuming, error-prone, and require a high level of operator expertise.

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