Research On Key Technology Of 3D Reconstruction Based On Coded Structured Light

3d reconstruction aims to reconstruct the 3d surface structure of the target object by using corresponding point matching,triangular ranging,point cloud fusion and other techniques.The flattening information of 2d image is transformed into more intuitive and accurate 3D information.Non-contact 3 d reconstruction based on coding structured light method,will not cause irreversible damage to the surface,and has low cost,high accuracy,the advantages of using flexible and convenient,obtained the rapid development,in the restoration,medical,industrial manufacturing,in areas such as unmanned has an irreplaceable role,but the technology is still lack of the following:Firstly,in the Zhang calibration method,the calibration plate theoretically only needs to capture the matrix of four feature points in three directions to obtain the required parameters through camera calibration,but in fact,too few patterns and feature points will lead to large errors in the calibration results.Second,due to the influence of equipment material properties and electronic circuit structure,noise will be introduced in the process of image acquisition and transmission,resulting in the degradation of grating pattern quality,resulting in errors in the decoding process,thus affecting the effect of 3D reconstruction.Thirdly,it is difficult to reconstruct the surface of complex objects using phase shift or gray code structured light 3d measurement technology alone,so most of the existing research is carried out based on combinational coding.However,the combination encoding method usually needs to project a large number of patterns to achieve the purpose of decoding,and the sinusoidal fringe decoding is complicated,which limits the application of structured light reconstruction technology in the field of real-time measurement.Therefore,how to reduce the number of projections and reduce the computational complexity is the key to the research of structured light reconstruction technology.In order to overcome the above shortcomings,this paper focuses on the following three aspects to carry out the research of structured light 3D reconstruction:1.In view of the lack of uniform constraints in existing camera calibration methods,accurate camera parameters cannot be obtained.In this paper,a large number of experiments of control variable method are set up to explore the influence of pattern number,feature points and target pose on camera calibration accuracy,and the best calibration scheme is obtained.The optimal calibration scheme is used to calibrate the system,and the reprojection error is less than 0.2.2.To solve the problem that grating patterns are affected by noise and result in large decoding error,this paper proposes two threshold functions with unbiased,continuous and high-order differentiable characteristics based on wavelet threshold denoising to improve the existing threshold denoising methods.Experiments show that the improved wavelet threshold denoising method achieves better denoising effect under different wavelet decomposition layers and different noises,and the reconstructed surface is smooth and continuous with small error.3.Due to the large number of projection patterns and high computational complexity,two new coding combinations,triangular phase shift complementary Gray code and three-frequency two-step heterodyne method,are proposed in this paper.The triangular wave function calculates the phase information by intensity ratio,which simplifies the calculation step.Secondly,this paper uses complementary gray code to decode the dislocation,so as to avoid the problem of order jump of fringe boundary.The triangular phase shift complementary Gray code scheme requires two triangular grating,four gray codes and one complementary gray code,a total of seven stripe patterns,to recover the surface structure of complex objects,and accelerate the reconstruction speed.The three-frequency two-step heterodyne method based on triangular wave has higher resolution and better reconstruction effect than dual-frequency heterodyne method,and only three groups of two-step triangular phase-shifting patterns with different frequencies are required for reverse reconstruction,which further reduces the number of projections.The effectiveness of the proposed method is proved by surface restoration of different experimental objects.