We propose an improved FTP based on bi-color grating projecting. Two individual sinusoidal fringe patterns with π phase difference can be decoded from the deformed bi-color sinusoidal fringe pattern captured by color digital camera. Accessing the two fringe patterns, we can not only eliminate zero order spectra but also automatically build a binary mask at the same time to mark the valid measurement area easily, by which unwrapping phase time is shorten as well as phase error from invalid area is not transferred into valid area; Furthermore, we can easily expand the captured non-full-field deformed fringe pattern to form full field fringe pattern to guarantee frequency resolution.
Three-dimension (3-D) digitization of tooth is becoming an important diagnostic tool of dentistry for the quantitative medicine investigations. In this paper, an optical measurement instrument for tooth data acquisition based on the principle of structured illumination was developed. The instrument consists of a structured illumination optics, a stepping motor driven phase shifting device, a commercial CCD camera system with frame grabber interface and a control personal computer. Because there is no possibility of watching the system directly in the mouth, the measurements were still restricted to plaster casts of the tooth. With a new calibration gauge, both the phase-height mapping and 3D coordinates calibration could be done simultaneously through only one measurement. Additionally, to recover complex shape distribution of the tooth, a phase unwrapping procedure is proposed. The effectiveness of the proposed method is demonstrated by experimental results.