A theoretical comparison of three fringe analysis methods for determining the three-dimensional shape of an object in the presence of noise

Various levels of random noise have been added to simulated digital images of a spherical dome illuminated by fringes projected from an offset angle. The noisy images have then been analysed using Fourier transform profilometry, phase shifting profilometry and spatial phase detection. The theoretical dome was subtracted from the domes reconstructed using these methods to form error maps. The maximum and RMS errors for each error map were calculated and plotted against the added noise level. At low levels of added noise the phase shifting method produced the lower errors, but above around 10% noise the Fourier transform method was better. Only at very high levels of added noise did the spatial phase detection method achieve the lowest errors. (C) 2002 Elsevier Science Ltd. All rights reserved.