Projection Colour Moiré Technique for 3-D Surface Reconstruction

Abstract

Moiré effect is an optical phenomenon that occurs in consequence of the coincidence of two periodical structures, gratings. Nowadays the moiré effect is used for contour generation of three-dimensional objects and measurements of deformation: strain analysis, linear or angular displacements and vibration analysis. Projection moiré method is a typical method for three-dimensional measurements. To find the absolute order of a fringe (z-coordinate of the object under research) one must define the difference in depth between two points by the moiré patterns. But to present day for extraction of an object´s three-dimensional information several moiré patterns and image processing methods such as Fourier-transform method, temporal phase shifting technique were needed, since from one moiré image it´s impossible to determine whether the object is concave or convex. It means that it was impossible to work with dynamic objects in real-time operation mode. Here we present colour moiré projection technique that resolves the arising problem of ambiguities in moiré patterns by application of only one moiré pattern. This method is based on application of colour rulings to gratings in projection moiré technique.