"2 + 1" absolute phase retrieval computer-generated moiré profilometry.

A "2+1" absolute phase retrieval computer-generated moiré profilometry is proposed. While two frames of sinusoidal fringe patterns with different spatial frequencies plus a uniform pattern with their shared direct current component are projected onto the measured object, the corresponding two deformed patterns and one background light pattern are captured, respectively. Then, the two alternating components of the deformed patterns are obtained by subtracting the background light pattern. By using a specific computer-generated moiré profilometry, both the high-frequency and low-frequency wrapped phases just caused by the measured object itself are extracted, and thus the absolute phase can be retrieved by using the relationship between these two frequencies. Compared with the traditional dual-frequency method, it reduces the number of projection frames and effectively improves the projection efficiency. Moreover, it relaxes the unit-frequency restriction of the conventional dual-frequency method.