Moire profilometry through simultaneous dual fringe projection for accurate phase demodulation: a comparative study

Abstract

In optical metrology, fringe projection and moire techniques have been widely used to measure the topography of objects. We can combine the advantages of the two techniques by applying a configuration of simultaneous dual projection in the fringe projection technique, which generates a superimposed fringe pattern containing a moire pattern that is phase modulated according to the topography. In this work, we present an analytic and comparative study of three methods to demodulate the phase of the moire pattern: the spatial, spatial-temporal, and temporal methods. Those methods consist of two steps: first, the moire pattern is extracted from the superimposed fringe pattern; next, the phase of the moire pattern is demodulated. The analytical results show that the resulting phase map has double phase sensitivity compared to that of the classical fringe projection technique. Experimental and numeric results prove the feasibility of this technique.

Removal of occluding shadows in fringe-projection profilometry by co-phasing simultaneous fringes

“…In 2021 a comparative study in digital moiré profilometry was reported by Sotero et al [28]. Their approach requires 9 or more grayscale phase-stepped fringe patterns to operate both projectors simultaneously, which allows decoupling the overlapping spectra of the composite fringe patterns.…”

Gamma correction in simultaneously dual fringe projection moiré profilometry

“…Most common FPP configurations consist of a multimedia projector and a camera, although, this setup can correctly scan free-form surfaces, it has recently proposed other configurations including two or more cameras and/or projectors to address the self-occluding shadows 5,6 or improving the setup's sensitivity/resolution [7][8][9][10] . The last approaches simultaneously project a gray-scaled sinusoidal pattern from two symmetrical directions, and then a camera records the superimposed pattern.…”

“…The estimation of this moiré phase consists of first isolating the moiré intensity and then retrieving its phase. To carry out these two methods, it has been proposed a purely spatial method 7 , spatial and temporal methods 8,9 , as well as a purely temporal method 10 .…”

Colored digital Moire technique for self-occluding shading in fringe projection profilometry

“…Since the FPP signal's nature has three variables -or more for distorting harmonics-the phase recovery from a single fringe pattern is an ill-posed problem in the Hadamard sense 5 . In order to overcome this issue, real-time applications need to introduce prior information like spatial phase carriers and/or color encoding as well as using two video projectors 3,[6][7][8][9][10][11][12][13][14] and references therein.…”