Color encoding of binary fringes for gamma correction in 3-D profiling

Abstract

Three-dimensional profiling by sinusoidal fringe projection using PSI-algorithms are distorted by the nonlinear response of digital cameras and commercial video projectors. To solve the problem, we present a fringe generation technique that consists of projecting and acquiring a temporal sequence of strictly binary color patterns, whose (adequately weighted) average leads to sinusoidal fringe patterns with the required number of bits, which allows for a reliable three-dimensional profile using a PSI-algorithm. Validation experiments are presented.

Binary coded triangular fringes for 3-D surface-shape measurement

“…The acquired patterns are decoded to the intensity gray levels, so that the function Ix; y may be reconstructed through the well-known formula [15] and the Matlab decoded function gray2bin, i.e.,…”

Gray coded trapezoidal fringes for 3-D surface-shape measurement

“…, I x y may be reconstructed through the well-known formula [16] and the Matlab decoded function gray2bin, i.e. …”

“…Gray codes or so-called binary reflected Gray codes are well suited for such binary encoding, since only one bit changes at a time. Also, the Gray codification could be advantageous to use because it is more error robust [16,17]. The proposed method is an improved of the approach called the trapezoidal phase-shifting method proposed by Huang et al [11].…”

Wrapping-free phase retrieval with applications to interferometry, 3D-shape profiling, and deflectometry

“…3D-shape profiling [1][2][3], strain analysis, temperature gradient measurements [4,5], testing of optical components [6,7], and surface deformation may be regarded as typical examples. Most of the established methods for phase determination, including phase-shifting interferometry [8][9][10][11], spatial interferometry [12], and Fourier-based techniques [13][14][15], evaluate the arctangent of the ratio of the intensity functions.…”