Abstract
Digital fringe projection measurement technology has been widely used in computer vision and optical three-dimensional (3D) measurement. Considering the phase error caused by the gamma distortion and nonlinear error, the active gamma precorrection and phase error compensation methods based on the three-frequency with three-phase shifts are designed to reversely solve the initial phase and accurately compensate phase error. On the one hand, the gamma coefficient of the measurement system depends on precoding two groups of fringe sequences with different gamma coefficients to calculate the corresponded proportional coefficient of harmonic component. On the other hand, the phase error compensation method is designed to compensate the phase error and improve the accuracy and speed of phase calculation after gamma correction. Experiments show that the proposed precalibration gamma coefficient method can effectively reduce the sinusoidal error in nearly 80 percent which only needs fewer fringe patterns. Compared with the traditional three-frequency with four-phase shift method, the proposed method not only has higher phase accuracy and better noise resistance but also has good robustness and flexibility, which is not limited to the gamma distortion model.
Highlights
Digital fringe projection measurement technology has been widely used in computer vision and optical three-dimensional (3D) measurement because of the advantages in their noncontact operation and full-field inspection [1]
A series of preencoded sinusoidal fringes are projected onto the measured surface, and the sinusoidal fringes are modulated by the height distribution of the measured surface, known as the deformed fringe; the phase method based on the multifrequency heterodyne is used to demodulate and calculate the phase distribution to obtain the 3D information of measured surface. is technology makes the structured light system more adaptive to operate
Gamma distortion will directly lead to the high harmonic component in the deformed fringes, which will affect the quality of the phase solution and bring measurement error to the 3D information
Summary
Digital fringe projection measurement technology has been widely used in computer vision and optical three-dimensional (3D) measurement because of the advantages in their noncontact operation and full-field inspection [1]. E high-speed 3D shape measurement method for dynamic scenes by using bifrequency tripolar pulse-width-modulation fringe projection was designed to generate ideal fringe patterns with slight defocus, but the gamma correction of projector and camera response nonlinearity would affect the phase unwrapping [7]. Aiming at the problem of the gamma effect and phase error compensation in digital fringe projection measurement, we propose a precoded method to calibrate the gamma coefficient which depends on precoding two groups of fringe sequences with different gamma values and calculating the corresponding harmonic component proportional coefficient. E experiment indicates that our method needs less projected fringe patterns and can effectively achieve high precision precalibration gamma coefficient and can break through the limitation of the gamma distortion model and be compensated well, which will make the measurement system more flexible and operate .
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