A novel phase-shifting profilometry to realize temporal phase unwrapping simultaneously with the least fringe patterns

Abstract

A novel phase-shifting profilometry (PSP) to realize temporal phase unwrapping (TPU) simultaneously with the least fringe patterns is proposed. By combining a unit-frequency ramp pattern with the least three phase-shifting sinusoidal fringe patterns at a shifted-phase of π/2 respectively, three composite patterns are formed. While these three composite patterns are projected onto the measured object successively, three corresponding deformed patterns can be captured by a CCD camera. After demodulation, both the unit-frequency component and the high-frequency components characterized by phase-shifting deformed patterns can be extracted efficiently. So the wrapped phase caused by the measured object can be calculated from the high-frequency components of the deformed patterns with PSP and the fringe orders can be derived from the unit-frequency components to pixel-wise auxiliary phase unwrapping. It employs no other additional structure pattern to achieve full-field phase unwrapping. The accuracy of the measurement is guaranteed by using three phase-shifting fringe patterns, and the combination of the TPU can measure the discontinuous surfaces or multiple isolated objects simultaneously. PSP and TPU are integrated skillfully with least fringe patterns in the proposed method. The experimental results demonstrated the feasibility and validity of the proposed method.