Pattern Projection with a Sinusoidal Phase Grating

Abstract

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.

Tunable Phase Gratings by Wrinkling of Plasma-Oxidized PDMS: Gradient Skins and Multiaxial Patterns

“…The use of wrinkling bilayers in the fabrication of tunable phase grating has been previously demonstrated with thin polymer films (deposited or laminated) supported onto an elastomer, such as polydimethylsiloxane (PDMS). − Grating efficiencies can be tuned by employing sinusoidal phase gratings, where the distribution of energy in the diffraction orders can be varied. , This property has applications in optics, such as projection systems, optical switches, and lasers . Transmission phase gratings are thin transparent optical elements that can consist of periodic refractive index variations or of a periodic surface relieves, and these can be fabricated exciting sinusoidal wrinkles on a surface.…”

“…22−24 Grating efficiencies can be tuned by employing sinusoidal phase gratings, where the distribution of energy in the diffraction orders can be varied. 25,26 This property has applications in optics, such as projection systems, 27 optical switches, 28 and lasers. 29 Transmission phase gratings are thin transparent optical elements that can consist of periodic refractive index variations or of a periodic surface relieves, and these can be fabricated exciting sinusoidal wrinkles on a surface.…”

Fringe projection with a sinusoidal phase grating

“…The rapidly varying contrast of the fringes due to the Talbot effect makes impossible profilometry of large-scale objects at plane-wave illumination. Indeed, the distance between the Talbot planes in this case is of the order of several centimeters [41]. To increase the spatial zone of equal contrast, the grating should be illuminated by a divergent beam.…”