Large-scale three-dimensional object measurement: a practical coordinate mapping and image data-patching method

In a practical three-dimensional (3-D) sensing system, the measurement of a large-scale object cannot be completed in only one operation. A relieflike object is generally divided into several subregions, an optical sensor pos itioned at each of these locations, and the shape of the whole object obtai ned by patching together all the 3-D data of the subregions. It is importan t to have accurate 3-D coordinates (x, y, z) for each subregion. We propose a new phase-to-height mapping algorithm and an accurate lateral coordinate calibration method with which to obtain the 3-D coordinates. After all the subregions are measured, it is necessary to transform the local coordinate s into global world coordinates; here we present a new image data-patching method based on a flood algorithm. This method provides the optimal path al ong which to patch all the subregions into the shape of the entire object. We have measured and successfully patched a large sandy pool (9 m x 5 m), a nd the reliability and feasibility of our method have been demonstrated by experiment. (C) 2001 Optical Society of America.