High-resolution, real-time fringe pattern profilometry

This paper presents some of our recent work on high-resolution, real-time 3D profilometry using a digital fringe projection method. In particular, we utilize the unique projection mechanism of a single-chip digital-light-processing (DLP) projector: sequential channel-by-channel switching. Three phase-shifted fringe patterns are encoded into the three primary color channels and switched naturally. A high-speed charge-coupled device (CCD) camera, synchronized with the projector, is used to capture each individual color channel of the projector. Because color is not desirable, the color filters of the projector are removed, and an external trigger signal is supplied to enable its projection. Since three fringe images are sufficient to reconstruction one shape, this technique can, theoretically, reach the refresh rate of a projector (typically 120 Hz). However, due to the speed limit of the camera used, the data acquisition speed is up to 180 fps, thus the 3D shape measurement speed can be as high as 60 fps, as it requires three images to recover one 3D shape. To reach simultaneous 3D data acquisition, reconstruction, and display, we developed various efficient algorithms, and used advanced graphics hardware techniques to boost the processing. In this paper, we will summarize the technologies we developed, and will present some of the research results.