Direct object shape detection based on skeleton extraction of a light line

Abstract

A simple, fast and accurate light line technique for direct detection of 3-D shape is presented. This technique is proved by simulation and experimentally verified. To obtain the surface shape, the object is moved along an axis with an electromechanical device and scanned by a projected light line. Based on the measurement of displacement that suffers the projected line on the surface, object high data is obtained. Light line displacement is acquired by determining the precise position of its maximum on the object's surface and is compared with that projected on a reference plane. The described method has the advantages over conventional fringe pattern contouring that it is not necessary to design software to obtain the fringe phase and a phase-unwrapping step does not have to be applied. Another advantage is processing time, because the maximum is extracted using an efficient algorithm to fit a concave function with the light line intensity profile. The technique is quite skilled, robust, and highly accurate, and it can obtain the form of an object with complicated surfaces even with difficult details such as occlusions and discontinuities. Line light displacement can be obtained with resolution of fraction of a pixel, and a surface height accuracy up to 0.001 mm can be obtained.