Direction-determined phase unwrapping using geometric constraint of the structured light system: The establishment of minimum phase map

A recently proposed absolute phase unwrapping method using geometric constraints of the structured light system significantly improves the measurement speed and the robustness. The most important step of this method is to create a minimum phase map as the phase unwrapping reference. Current method usually selects the closest plane as the minimum phase map. However, we found that the position of the minimum phase map is direction-determined and it may induce a fatal error to phase unwrapping under certain circumstances. This letter analyzes the direction-determined phase increasing phenomenon and presents a direction-determined phase unwrapping technique, which includes a new establishment method for the minimum phase map and corresponding phase unwrapping procedures.