Phase unwrapping using geometric constraints for high-speed fringe projection based 3D measurements

A new methodology for 3D surface measurement based on phase shifted fringe pattern projection is presented which enables real-time measurement and high-speed performance of 3D measurements using stereo camera observation. The essence of the new technique is a drastic reduction of the fringe code which makes the process of pattern projection and image recording faster and real-time applicable. The new algorithm allows the complete omission of the typically used Gray code sequence or other additional code to the phase shifted sinusoidal fringe sequence. Its main concept is a special geometric design of the arrangement of the projection unit in relation to one of the involved cameras. The 3D point calculation is performed by triangulation between the two cameras with the help 3D point determination between the projection unit and one of the cameras. Whereas the second mode ensures the uniqueness, mode one realizes the accurate calculation. The realization of the uniqueness of the measurement is obtained by a corresponding arrangement of the parameters projected fringe width, the measurement volume size, the triangulation angle between the principal rays of first camera and the projection unit, and camera constants of second camera and projection unit. First experiments with a 3D measurement systems based on fringe projection technique show the robustness of the new method. Real time measurements can be performed which is the precondition of the supervision or quality check of several dynamic processes.