Self-Coding Phase Shift for Absolute Phase Retrieval in Fringe Projection Profilometry.

Phase unwrapping is the core of phase shift profilometry. Conventional phase unwrapping usually requires the projection of additional patterns or other constrains to unwrap the high-frequency wrapped phase into absolute phase, which increases time consumption and complicates measurement procedures. To solve this problem, we propose a self-coding phase shift (SCPS) method for retrieving the absolute phase. Two sets of codes are encoded into the projection patterns, namely, the De-Bruijn sequence code and the phase gradient code. The fringe order can then be determined by combining these two different encodings. The proposed method does not require any prior information and only demands four phase shift fringes. Experimental results demonstrate that the SCPS method is highly robust and accurate in measuring both complex and separated objects.