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Self-calibrating phase-shifting interferometry of three unequal phase steps by fitting background light to a polynomial of degree K.

This paper presents a novel non-iterative and robust algorithm in phase-shifting interferometry of three unknown and unequal phase steps. First, the modulation light and the object phase are algebraically eliminated; second, the background light is approximated to a 2-D polynomial of degree K and estimated by applying the least squares method; third the phase steps are obtained, and finally, the object phase is computed. This idea is theoretically described and verified numerically and experimentally for several values of K.