Directly recognizing and removing the projector nonlinearity errors from a phase map in phase-shifting fringe projection profilometry

Abstract

Abstract In phase-shifting fringe projection profilometry, the projector nonlinearity has been recognized as one of the main error-inducing factors, especially when only very few fringe patterns are available. For solving this issue, this paper presents a simple and effective method, that allows us to recognize and remove, directly from a calculated phase map, the nonlinearity-induced errors without calibrating the projector luminance or the phase errors in advance. In implementation, after filtering the phase map using a low-pass filter, we estimate the phase error coefficients by exploiting the dependence between the isolated artifacts and the smoothed phases under 3-sigma criterion. Furthermore, using the phase error function just estimated, the phase errors are corrected in a pointwise way through fixed-point iterations. Experimental results demonstrated that this method offers some advantages over others, such as being independent of a special nonlinearity model, being easy to implement and not requiring a prior calibration, protecting the edges and details of the measured shape from being blurred, and enabling dealing with time-variant projector nonlinearities.