The aim of this work is to study the diffractive properties of a sinusoidal phase grating for incorporation as a pattern projection element in a multisource and multicamera phase-shifting profilometric system. Two challenges should be overcome for successful operation of such a system, which are connected to inherent limitations of the phase-shifting algorithm-requirements for a sinusoidal fringe profile and for equal background and contrast of fringes in the recorded patterns. As a first task, we analyze the frequency content of the projected fringes in the Fresnel diffraction zone for parallel and divergent light illumination at different grating parameters and wavelengths. As a second task, we evaluate the systematical errors due to higher harmonics and multiwavelength illumination. Finally, operation of the four-wavelength profilometric system is simulated, and the error of the profilometric measurement evaluated. The results of test measurements are also presented.
A single-shot fringe projection profilometry system based on simultaneous projection of four phase-shifted sinusoidal fringe patterns generated at four different wavelengths is described. The system includes a fringe pattern generation module containing four blocks with four near-infrared diode lasers and a registration module with four CCD cameras. In order to simplify the technical solution and to avoid the stringent requirement for stability in the case of interferometric fringe generation, we study both theoretically and experimentally realization of the proposed system by using of a phase grating as well as a holographic optical element for reconstruction of two point sources. The results of the measurement ofthe relative and absolute coordinates oftest objects for both types ofdiffraction gratings are presented.
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