Three-dimensional measurement system and calibration method for millimeter-scale physical gratings

The fringe projection device composed of LED and grating plate has the advantages of low cost, high integration and easy control. Combined with the micro-camera module, the visual measurement system proposed in this paper can fulfill the demand of 3D measurement of the morphology of narrow internal cavities, which are difficult to be probed by the conventional fringe projection 3D measurement system. As the key component of the proposed measurement system, the structural parameters of the projection device are closely related to the phase shift of the projected fringes, which at the same time constrains the accessibility of the vision system. In this paper, a projection device that can project four-step phase- shifted fringes is designed, while a millimeter-scale vision measurement system is built, and the corresponding system calibration method is proposed. Finally, the performance of the projection device is verified by three-dimensional topography measurement experiments.