Stair phase-coding fringe plus phase-shifting used in 3D measuring profilometry

Abstract

As the number of codewords adopted in phase-coding fringes increases, the solution of fringe orders leads to many mistakes. Consequently, errors of the unwrapped phase occur. Thus, increasing the codeword approach in a phase-coding fringe remains a challenge. In this paper, a modified stair phase-coding fringe is designed, and a new phase unwrapping algorithm based on shifting fringe order is presented. The main idea of this method is that the width ratio between the sinusoidal fringe and each stair phase of phase-coding fringe is set to 1: n. The fringe order retrieved from the phase-coding fringe can be multiplied by the shift itself, thereby assisting phase unwrapping. This method adopts fewer codewords to replace the usual large number. As such, the approach gains two merits. One is that it guarantees a high measurement accuracy. The other is that it allows the measurement of isolated objects with complicated shapes. The experiments demonstrate that the proposed method is simple but effective.

Absolute Phase Retrieval Using One Coded Pattern and Geometric Constraints of Fringe Projection System

“…Note that line O c O p is parallel to the reference plane, so points O c and O p have the same distance L from the reference surface. Based on the triangulation principle, the height of the measured objects can be computed as [30]:…”

Robust wrapping-free phase retrieval method based on weighted least squares method

“…Apart from those methods mentioned above, many temporal phase unwrapping methods are proposed to unwrap the phase of the object with large discontinuities and isolated parts [18][19][20][21][22][23][24]. But they need many frames of fringe images which would take much time.…”