An optical measurement method of 3-dimensional surface profiles which is named the slit beam projection is suggested. This method is intended especially for noncontact and fast dizitization of clay models for die manufacturing. Its basic principles are based on geometric optics. A reconstruction algorithm of 3-dimensional profiles in the slit beam projection adopted the finite element method is newly suggested in which multiple calibration planes are used for acquiring the 3-dimensional coordinate of a point to be measured. Also, an image processing algorithm is newly suggested and practically implemented. The method is that the discrete intensity distributions of a column in a slit beam image fit into a polynomial function and then the coordinate with maximum intensity is detected by using numerical methods. The experimental results show that the slit beam projection is very effective in terms of measuring time and resolution being compared with conventional contact type dizitization technique using stylus probes. The 3-dimensional profile measurement system of live human faces, which was developed specially for Kumdori sculptor robot of the '93 Taejon Exposition, is presented and practically developed. The measurement system is based upon optical triangulation method such as the slit beam projection in which multiple slit beams are designed to simultaneously project onto the the face of a spectator in order to minimize measuring time. Images of the projected beams are then captured successively by CCD camera and processed in a microcomputer to reconstruct the whole profile of the face for automatic sculpturing by an industrial robot. A new method of moire topography is suggested in which a slit beam in a scanning mode to generate moire fringes. One remarkable feature of this method is that, as opposed to existing shadow and projection types, height differences between two consecutive fringes become constanst so that absolute fringe orders need not be identified. This advantage makes it possible to measure 3-dimensional surfaces profiles in an automatic manner simply by using a computer-aided image-processing technique.
