# A Binocular Vision-Based 3D Sampling Moire Method for Complex Shape Measurement
## 5 Conclusions  
Based on the binocular vision model and sampling moire method, a universal 3D sampling moire method was developed in this study. The main conclusions are as follows:  
1. Based on the binocular vision model, the \(y\) direction parallax in the left and right images can be eliminated through epipolar rectification. On that basis, a phase correction method for sampling moire was developed to solve the phase match problem of sampling moire at different visual angles, and accurate measurement of 3D shapes by sampling moire was achieved.
2. Through numerical simulation, 3D sampling moire and 3D-DIC were compared in terms of measurement accuracy and anti-noise capability, and the influence of sampling pitch and fringe patterns on the measurement accuracy was analyzed. The results showed that the 3D sampling moire method has the same level of measurement accuracy as 3D-DIC, but its anti-noise capability is much better than that of DIC. In the experiment, a sampling pitch close to the fringe pitch was selected, effectively reducing the measurement error. Compared with the traditional phase shifting method, sampling moire is insensitive to the distortion of fringe patterns, so it is more effective for deformation measurement in a complex environment.
3. A three-point bending loading configuration was used for experimental verification of the measurement accuracy of 3D sampling moire. The measurement results of 3D sampling moire were compared with the linear displacement of the high-precision stepping motor, indicating that the average measurement error of the out-of-plane displacement was 31 \(\upmu\)m. Three-dimensional sampling moire has the same level of measurement accuracy as the phase shifting method, but has higher measurement efficiency because only one image is necessary for phase analysis.  
Figure 10: Measurement of cantilever beam deflection. (**a**) Cantilever structure, (**b**) Deflection after printing, (**c**) Printed results at different scanning speeds, (**d**) Deflection at different scanning speeds.  
4. The cantilever configuration was designed and DED carried out to print a cladding layer on the beam surface. The deflection deformation caused by the residual stress with different printing parameters was experimentally characterized based on the 3D sampling moire method. The effective experimental results showed that this method is applicable to the deflection measurement, which has the potential for the analysis of residual deformation and stress arising in additive manufacturing processes.  
Conceptualization, W.S.; Methodology, W.S. and Q.Z.; Software, W.S. and Q.Z.; Supervision, H.X.; Writing--original draft, W.S.; Writing--review & editing, W.H. and H.X. All authors have read and agreed to the published version of the manuscript.  
This work was financially supported by the National Natural Science Foundation of China (Grant Nos. 12032013, 11972209, and 11802156), the National Key Research and Development Program of China with grant No. 2017 YFB1103900, and the National Science and Technology Major Project (2017-VI-0003-0073).  
Not applicable.  
The authors declare no conflict of interest.