A method of depth extension in 3D shape measurement by geometric constraints

In this paper a new method to extend the measurement depth limited by geometric constraints for objects with large depth variances is presented. This method mainly includes the following steps: (1) using the watershed image segmentation algorithm to extract the correct part of the discontinuous absolute phase distribution obtained by geometric constraints, and making a binary mask of the correspondent region; (2) using the window Fourier filter-quality guided phase unwrapping algorithm to obtain the relative phase distribution of the tested object; (3) using the binary mask to get the difference between the relative and the absolute phases; (4) converting the relative phase distribution to absolute phase distribution by referring to their phase difference in the mask region. The experimental results prove the effectiveness and correctness of the proposed method.