Moving-correlation-code triangulation range imaging

A new method is described for obtaining accurate range images at high sped in a low-cost instrument. A prototype has been built and tested, and a patent application submitted. The method resembles grid-coding in that a camera and a stripe projector are directed at a scene, but the projector is different. It consists of a thin light source on the axis of a turntable, and a binary mask conforming to a cylinder coaxial with this. The mask has alternate black and clear stripes parallel to the axis. It forms a DeBruijn sequence, i.e., a sequence in which all possible sub- sequences of given length occur. No lens is used, deliberately smoothing the resulting illumination. In operation, the turntable rotates, and six consecutive images are taken at uniform intervals. A given pixel records six consecutive samples of a scene point. This six-vector, when normalized to unity to accommodate reflectance variations, is unique to the place in the sequence form which it came. Thus we can compute the position in 3-space of the surface point at which the pixel is looking. Observed accuracy is .1 millimeter at 30 centimeters range.