Research On Structured Light 3D Reconstruction Of Improved Multi-frequency Multi-step Phase-shifting Algorithm

The 3D measurement technology based on structured light has high research and application value in the field of 3D measurement because of its high accuracy,wide adaptability and strong robustness.Multi-frequency multi-step phase-shifting algorithm is widely used in structured light technology.N-step phase-shifting algorithm is used to solve the wrapped phase,and then multi-frequency heterodyne is used to solve the fringe orders corresponding to the wrapped phase of multiple frequencies.Finally,the absolute phase is obtained.Multi-frequency multi-step phase-shifting algorithm is insensitive to harmonics up to an arbitrary order and can suppress the nonlinear response of the system,so it has high measurement accuracy.However,due to the need for N-step phase-shifting patterns with multiple frequencies,the traditional algorithm needs to encode many fringe patterns,resulting in low efficiency of image projection and acquisition.This paper studies the measurement accuracy and efficiency of structured light system,designs the coding and decoding algorithm of structured light,and establishes the accuracy model of the system.The specific work is as follows:1)An improved structured light coding and decoding algorithm is proposed.In order to improve the efficiency of projection and image acquisition,an improved multi-frequency multi-step phase-shifting algorithm is proposed.Taking three-frequency three-step phase-shifting algorithm as an example,the improved algorithm only needs three phase-shifting patterns of the highest frequency,and one pattern for each of the other two frequencies.The number of patterns required is reduced from 9 to 5,and the efficiency is improved by 44.4%.The correctness and feasibility of the algorithm are verified by simulation.2)The proposed algorithm is verified by experiments.Firstly,the whole process of system reconstruction is introduced,the experimental platform is built,and the internal and external parameters are calibrated.Then,several experiments are designed to verify the reconstruction accuracy of the proposed algorithm,the reconstruction ability of complex and discontinuous objects,the reconstruction stability under different illumination conditions and the reconstruction stability of color objects.3)The accuracy model of monocular structured light measurement system is established.Considering that the reconstruction accuracy is affected by many factors,such as the position relationship between the measurement system and the object to be measured,the structural parameters of the system and so on.Through theoretical derivation,numerical simulation and experiment,the influence of system parameters on the overall accuracy of the system is analyzed,including the angle between the optical axis and the baseline of the camera and projector,the horizontal and vertical projection angles of the camera and projector,the focal length and the object distance.The reasonable range of system parameters under different conditions is given.The results of this paper effectively improve the efficiency of image projection and acquisition in high-precision reconstruction of structured light.The accuracy analysis of system parameters has a certain guiding significance for the construction of system structure.