Absolute measurement using field-shifted moiré

Phase shifted moire interferometry is one of the most effective tools for obtaining a full-field depth map. The major draw back of the technique is the two pi ambiguity which limits the measurement depth range to one fringe or requires the counting of fringes across the image. In either case, only a relative measurement is obtained, no information is available about the absolute distance to the camera. By moving the moire projection system (field shifting) the period of the moire pattern is changed allowing extraction of absolute depth information. We have built an instrument, employing field shifted moire to produce a full field depth map with 12 bits of depth resolution. The performance and applications of this instrument are discussed.