Research On High Speed And High Dynamic Range 3D Measurement And Error Correction Based On Fringe Projection

Fringe projection 3D measurement is widely used in aerospace,shipbuilding,automotive industry and other fields due to its advantages of high accuracy,noncontact,high efficiency and low cost.Speed and accuracy are key technical indexes of fringe projection 3D measurement technology.To improve measurement speed and accuracy and enhance universality of measurement scenes,based on the basic principle of fringe projection 3D measurement,this thesis focuses on key issues such as high-speed measurement,high dynamic range surfaces measurement and phase error compensation.The specific research content is as follows:(1)The principle of fringe projection 3D measurement is studied.The phase shifting method and the three pitches heterodyne method are used to calculate accurate phase information.According to the modulation intensity,an invalid region mask is established to remove invalid pixel information.The projector is regarded as an inverse camera to carry out system calibration.And the point cloud coordinates are calculated by triangular stereo model.Establish a fringe projection 3D measurement system and conduct experiments to lay the foundation for subsequent research.The results show that the measurement method used can stably and accurately calculate the 3D information of objects.(2)Aiming at the problem of low measurement efficiency caused by the large number of fringe patterns captured by traditional phase shift profilometry,A phase unwrapping method using single frequency phase shifting fringe patterns is proposed.The wrapped phase calculated by the phase shift method is unwrapped according to the preliminary unwrapped phase calculated by Fourier transform profilometry.The proposed method only needs to capture single frequency phase shifting fringe patterns to calculate object phase information.Simulation and experiments have shown that the proposed method reduces the number of fringe patterns by 66.7% compared to phase shift profilometry.The loss of object detail information caused by Fourier transform profilometry spectrum selection is avoided.It has higher phase accuracy and is insensitive to the selection of filters.(3)As an optical measurement method,fringe projection 3D measurement technology will have poor measurement effect due to overexposure or too dark of the fringes when measuring high dynamic range surfaces.In order to solve this problem,an adaptive fringe projection measurement method using speckle pattern for pixel matching is proposed.The metal workpiece and color surface were measured.The root mean square error of them were reduced from 0.314 mm and 0.182 mm to 0.105 mm and 0.123 mm respectively.Better than the methods before,only three additional patterns are needed to be projected to realize the measurement of the HDR surfaces.The experimental results show that the proposed method can reduce the number of projected patterns by more than 59.5% while achieving similar measurement accuracy,which greatly improves the measurement efficiency.(4)Aiming at the periodic phase error caused by the projector gamma effect,firstly,the influence of the projector gamma effect on the phase error is theoretically analyzed.And the characteristics of the phase error are verified through simulation and experiments.Then,it is proved that the projector used in the experimental system has the same gamma value in the center and around the projector.Finally,the gamma precorrection method is used to solve the system phase error problem.The experimental results show that the root mean square error of the unwrapped phase after correction was reduced from 0.19 rad to 0.03 rad.The precorrection method can reduce the phase error by more than 83% by only performing a precorrection on the system before measurement.This thesis has 80 figures,8 tables,and 88 references.