Three Dimensional Reconstruction And System Via Dual-projection Structured Light Based On Phase Measurement Profilometry

Structured light is a high-precision 3D reconstruction technology,which has a wide range of applications in the fields of precision measurement,reverse engineering,stomatology,cultural relic restoration and 3D modeling of human bodies.The traditional structured light based on phase measurement profilometry adopts a single camera and single projection mode.This research is relatively mature,but it cannot obtain the threedimensional overall information of the measured object at one time.To obtain the 3D overall information of the object,the synchronous reconstruction of the multi-camera multiprojection structured light system is absolutely the main solution.In view of the gamma distortion effect,the phase error unwrapping caused by discontinuity and noise in the phase measurement profilometry used in the dual-projection structured light system,and the difficulty in separating the aliased phase-shift pattern caused by the simultaneous projection in the dual-projection structured light system,In this thesis,a robust 3D reconstruction scheme of orthogonal double-projection grating structured light is proposed.The researches on the calibration of the dual-projection structured light system,robust gamma correction,robust spatial phase unwrapping and orthogonal grating coding,lay a theoretical foundation for the 3D reconstruction of multi-structured light systems.1)Research on system gamma distortion correction method.To solve the problem of gamma distortion in the case of projector focusing,a gamma self-correction method based on Gaussian eigenvalue encoding is proposed,which can be used for system calibration in automated 3D measurement scenes.The method adopts the combination of offline table building and online calculation,and the gamma-Gaussian eigenvalue mapping function constructed offline is used for online calculation of gamma value.Further,considering the defocusing effect of the projector,it can be known by analyzing the phase error function that the defocusing of the projector only affects the width of the wrapped phase distribution but not the amplitude.Therefore,a method to encode the phase chord distribution using Duty Ratio(DR)is proposed.Simulation and experimental results show that both the gamma self-correction method proposed in this thesis and the gamma correction method proposed in this thesis can obtain more accurate reconstruction results when the projector is focused.2)Research on robust spatial discontinuous phase unwrapping method.Aiming at the problem of wrong phase unwrapping caused by discontinuous phase and noise pollution in the wrapped phase,a weighted least squares phase unwrapping method based on least squares direction estimator is proposed.The least squares direction estimator uses a quadratic error norm to constrain the distance between the gradient and the direction vector to reduce the influence of noise on the direction estimation.The weight mask of the weighted least squares phase unwrapping is obtained by post-processing the orientation estimator with bilateral filtering,structural texture decomposition and smoothing,and numerical relabeling.The simulation and experimental results show that the proposed method can still obtain a better segmentation effect for discontinuous positions when there is noise in the wrapping phase.3)Research on phase calculation of orthogonal dual-projection aliasing gratings.Aiming at the problem that the aliasing patterns are difficult to separate due to the interference-like blur caused by the aliasing patterns projected synchronously by the dualprojection structured light system,a phase calculation method of aliasing gratings based on orthogonal dual-projection is proposed.The frequency and gray value of the dual-projection grating pattern are set based on the condition of signal orthogonality in wireless communication,and the discrete Fourier transform is performed on the aliased grating pattern in temporal domain to obtain the wrapping phase corresponding to each projector.The experimental results show that the coded orthogonal grating can avoid the interferencelike blur when the image is aliased,so that the phase with higher precision can be directly obtained.Finally,the three-dimensional reconstruction of the measured object by the dualprojection structured light system is completed by fusing the obtained point clouds.