Multiresolution 3D measurement using a hybrid fringe projection and moire approach

Projected fringe methods have lead to a wide selection of commercial sensors for 3D measurement applications. The basis of these systems is a projector such as an LCD presentation projector that is used to generate a coarse pattern that is shifted across the part and viewed by a camera. Three or more images with a small pattern shift between each are sufficient to obtain a detailed 3D map using phase shift analysis methods. The limitation of these systems has been that to obtain high resolution the system is limited to viewing only a small field-of-view. Moire methods are a way to leverage this resolution, particularly on flat or only slightly contoured areas. The approach described here takes advantage of moire methods used in connection with the fringe projection method to provide high resolution over key reference areas, while still provided a less precision measurement over a larger region.