Color-fringe pattern profilometry using a generalized phase-shifting algorithm

Abstract

In order to overcome the limitations of the sequential phase-shifting fringe pattern profilometry for dynamic measurements, a color-channel-based approach is presented. The proposed technique consists of projecting and acquiring a colored image formed by three sinusoidal phase-shifted patterns. Therefore, by using the conventional three-step phase-shifting algorithm, only one color image is required for phase retrieval each time. However, the use of colored fringe patterns leads to a major problem, the color crosstalk, which introduces phase errors when conventional phase-shifting algorithms with fixed phase-shift values are utilized to retrieve the phase. To overcome the crosstalk issue, we propose the use of a generalized phase-shifting algorithm with arbitrary phase-shift values. The simulations and experimental results show that the proposed algorithm can significantly reduce the influence of the color crosstalk.

Fourier analysis of RGB fringe-projection profilometry and robust phase-demodulation methods against crosstalk distortion

“…It is a well-known fact that most single-sensor color cameras have overlapping sensibilities [9]. Therefore, when using this kind of cameras for fringe projection profilometry, RGB crosstalk distorts the recorded data and some compensation algorithm is required [2][3][4][5][6]. In practice, assuming the crosstalk phenomenon to be linear, we have:…”

“…Phaseshifted fringe patterns distorted by RGB crosstalk have non-sinusoidal profiles and their phase-steps differ from the nominal value, which is particularly challenging for few-step algorithms [10][11][12]. In order to improve the quality of the measured phase proportional to the object's profile under study, crosstalk compensation is required before feeding the data into the 3-step PSA [1][2][3][4][5][6]. Other common practices in fringe projection include gamma correction and projection defocusing in order to obtain more sinusoidal profiles [1- 6,[13][14][15].…”

Three-dimensional shape measurement for thin objects based on hue-height mapping using color-encoded fringe projection

“…In view of this, many efforts have been made to improve the performance of phase measuring profilometry (PMP) in dynamic objects and real-time inspection fields. Color phase shifting technique (Cao and Su, 2002, Flores et al, 2015; Huang et al, 1999; Ma et al, 2011; Pan et al, 2006) is one of the single-shot 3D shape measurements, which overcomes the real-time limitations of PMP. A traditional color phase shifting method was proposed by Huang et al (1999) that projecting a color fringe pattern composed by three phase shifting sinusoidal fringe patterns coded into red (R), green (G) and blue (B) channels separately.…”

Grayscale imbalance correction in real-time phase measuring profilometry

“…Crosstalk matrix and coupling matrix [16] work well for addressing these problems, but they are obtained in a tedious procedure. The influence of the color crosstalk is well reduced by Huang et al [17] and Flores et al [18], but the color crosstalk can not be addressed completely. In addition, because Flores et al ignore the color imbalance, the color imbalance is not addressed.…”