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

Abstract

We present a method for synthesizing triangular intensity fringes as a way to solve the problems caused by projector/camera gamma nonlinearity in triangular-pattern phase-shifting profilometry. The fringe generation technique consists of projecting and acquiring a temporal sequence of strictly binary color patterns (code gray), whose (adequately weighted) average leads to triangular fringe patterns with the required number of bits, which allows a reliable three-dimensional profile reconstruction using these methods. Validation experiments are presented.

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

“…Eq. A4 given in [17] and using calibration algorithms described in [18], the 3-D profile is obtained, and is shown in the Fig. 9(d).…”

“…4, and a value ranging from -1 to ( ) ( ) 2 max , 1 R x y − . To retrieve the 3-D surface coordinates of the object from the intensity-ratio map, an intensity-ratioto height conversion algorithm is needed (see [14,17]). The calibration of our system is based on a linear calibration methods used in sinusoidal phase-shifting algorithms [18].…”

“…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].…”

3D Face Profilometry Based on Galvanometer Scanner with Infrared Fringe Projection in High Speed

“…Wang [16] proposed a binarized dual phase-shifting approach to improve the phase quality, which can realize error reduction for the binary defocusing technique while maintaining its advantage of 1-bit projection with high-speed. Flores et al [17] proposed a method to solve the problem of gamma nonlinearity in triangular-pattern phase-shifting profilometry by using synthesizing triangular intensity fringes. All of the above methods modify the DLP projector based on the characteristics of 1-bit fast projection.…”

3D shape measurement with binary phase-shifted technique and digital filters

“…The advantage of the method is that it is applicable to any commercial camera and video projector without previous calibration, although its drawback is the large number of frames to be acquired to retrieve the surface profile. Some works deal with the issue of generating sequences of binary images to synthesize high-quality sinusoidal, triangular or trapezoidal fringe patterns in a given direction 12,13 .…”