title: Fringe projection with a sinusoidal phase grating.
abstract: Phase-shifting profilometry requires projection of sinusoidal fringes on a 3D object. We analyze the visibility and frequency content of fringes created by a sinusoidal phase grating at coherent illumination. We derive an expression for the intensity of fringes in the Fresnel zone and measure their visibility and frequency content for a grating that has been interferometrically recorded on a holographic plate. Both evaluation of the systematic errors due to the presence of higher harmonics by simulation of a profilometric measurement and measurement of 3D coordinates of test objects confirm the good performance of the sinusoidal phase grating as a projective element. In addition, we prove theoretically that in comparison with a sinusoidal amplitude grating this grating produces better quality of fringes in the near-infrared region. Sinusoidal phase gratings are fabricated easily, and their implementation in fringe projection profilometry facilitates construction of portable, small size, and low-cost devices.
authors.affiliation: Central Laboratory of Optical Storage and Processing of Information, Bulgarian Academy of Sciences, Acad. G. Bonchev, Bl. 101, P.O. Box 95, 1113 Sofia, Bulgaria. elena@optics.bas.bg
authors.forename: Elena
authors.initials: E
authors.lastname: Stoykova
authors.forename: Georgi
authors.initials: G
authors.lastname: Minchev
authors.forename: Ventseslav
authors.initials: V
authors.lastname: Sainov