Three-dimensional shape reconstruction by phase-shifting shadow moire

Shadow moiré shows contour lines of an object with respect to a master grating plane; they result from the interference between the lines of the master grid and their shadow projected by a point source of light. In best cases the sensitivity of this procedure is a few tenths of a millimeter. The introduction of a phase-shifting procedure gives a better resolution, but the problem in practice is how can we shift the phase of the interferogram into shadow moiré? A complete study is presented showing the influence of different parameters. It is shown that only one possibility is available. Some applications to threedimensional shape reconstructions are presented with an accuracy of 0.01 mm, showing that the potentiality of shadow moiré is greatly improved.