Multi-view 3D Structured Light Based Combined Binary Coding Defocusing Projection Measurement And System Implementation

The structured light measurement technology is widely used in the detection of various complex and fine components in the 3C electronics manufacturing industry due to its advantages such as fast measurement speed and high measurement accuracy.However,in the traditional structured light measurement technology,the projector has a nonlinear gamma effect and the highest frame rate is only 120 Hz,and the camera needs to be accurately synchronized with the projector,which limits the accuracy and speed of the structured light measurement.To this end,this paper conducts in-depth research on structured light 3D measurement technology,and proposes related algorithms which include combined binary fringe coding and decoding algorithm,high-speed triggering of camera and projector,and calibration of defocusing system parameters based on defocused projection to improve the efficiency of 3D measurement while ensuring measurement accuracy.To meet the needs of large-scale multi-view measurement,a point cloud fast registration algorithm is proposed,and a structured light 3D measurement system based on defocused projection is developed and implemented.The main contents of this paper are summarized as follows:(1)The article thoroughly investigates the current research status of structured light defocusing measurement methods and multi-view point cloud registration algorithms at home and abroad.Many existing algorithms such as the binary coding methods,phase error compensation and phase unwrapping algorithms,calibration algorithm of the defocusing system parameter and point cloud fast registration algorithms are summarized and compared in the paper.Clarifying the key problems in high-speed and high-precision structure light defocusing measurement method and point cloud fast registration;(2)Aiming at the contradiction between high speed and high precision in structured light defocusing measurement,a combined binary fringe coding method using SBM fringes in the low frequency stage and improved SD fringes in the high frequency stage is proposed based on the research of binary fringe coding.Based on the frequency domain analysis and phase error analysis,the mathematical model of the phase error of the combined binary fringe is established.Then a phase unwrapping algorithm that performs error compensation in the wrapping phase is proposed to speed up the projectedbinary fringes speed while ensuring the highest measurement accuracy,thereby achieving high-speed and high-precision structured light defocusing measurement.(3)For the shortcomings of ordinary commercial projector such as non-linear Gamma effect and low projection frame rate,it is proposed to use programmable projectors instead of ordinary commercial projector.Then the paper study the high-speed trigger pattern of the programmable projector,and design the method of synchronous triggering of the programmable projector by the camera to achieve high-speed projection;Aiming at the dual problems of difficult calibration and poor calibration accuracy of the defocusing measurement system,the camera imaging model and the defocusing imaging principle of the programmable projector are analyzed by determining the measurement system defocusing method that the programmable projector is out of focus.The camera and programmable projector are calibrated with high precision by using Zhang'calibration method and achieving phase mapping based on combined binary fringe with error compensation.(4)For the problems of low registration efficiency and poor registration accuracy of multi-view 3D point clouds,a fast registration method of multi-view point clouds based on precision motion platform is proposed;This method first needs to remove the outliers based on statistical filtering method and down sample the point cloud by using voxel filtering method to achieve point cloud preprocessing for avoiding affecting the registration accuracy;Aiming at the problem of misalignment of point cloud registration based on precision motion platform,it is proposed to realize the calibrate algorithm of precision motion platform and measurement system based on the projection angle of two coordinate systems,and achieve high-precision point cloud registration through angle compensation.(5)According to the above research methods and theoretical knowledge,various algorithms and system function modules are implemented by combining various toolkits such as C++ programming language,image processing library(Open CV)and point cloud processing library(PCL)in the paper.And a high speed and high precision multi-view structured light defocusing measurement system that can develop point cloud fast registration based on the Qt Graphical interface application.The feasibility andeffectiveness of the proposed method and measurement system function in this paper are verified by measuring several objects,and the measurement speed and accuracy of the defocusing measurement system are also measured by using the groove standard block.