Visual Measurement And Object Reconstruction Based On Forward And Inverse Gray Code And Phase Shift Period Dislocation Correction

Because structured light 3D measurement technology can completely restore the3 D shape,color and other information of the measured object,it has the advantages of simple operation,non-contact,high precision and so on.And it is widely used in finance,education,commerce,industry,aviation and many other fields.As a typical structured light three-dimensional measurement method,the Gray code plus phase shifting fringe not only has the characteristics of large range and strong anti-interference of Gray code,but also have the advantage of high precision of phase shift.The only drawback is that the measured value of both Gray code decoding and the wrapped phase shift in the actual environment are prone to dislocation at the jump position.As a result,the obtained measurement value of unwrapped phase will have phase unwrapping error.This error will cause gross measurement error of 3D reconstruction object in the subsequent 3D measurement,and its accuracy will decrease rapidly.This dissertation mainly studies a three dimensional measurement method of Gray code plus phase shifting fringe.To solve the problems of dislocation of Gray code decoding value and wrapped phase,a correction phase unwrapping error method is proposed,so as to realize the high accuracy 3D measurement and reconstruction of the object.Firstly,the measurement model of structured light 3D measurement system is built.The 3D measurement principle of traditional Gray code plus phase shifting stripe is studied,which include the principle of sinusoidal phase shifting method,Gray code encoding and decoding,phase unwrapping principle based on Gray code and the generation mechanism of phase unwrapping error.3Dmax software is used to build a structured light 3D measurement simulation system.Based on this system,three dimensional measurement method of traditional Gray code and phase shifting fringe is used to simulate the measurement experiment of the standard plane,the head statue with complex surface shape and two isolated objects composed of a ball and a teakettle.The simulation results show that there are phase unwrapping error points in the traditional Gray code plus phase shifting stripe 3D measurement method.Then,in order to improve the accuracy of Gray code decoding,an image binarization method based on forward and inverse Gray code pattern is studied.Based on the research of the generation mechanism of phase unwrapping error,this dissertation come up with a correction phase unwrapping error method to eliminate the phase unwrapping error.Thus a three-dimensional measurement method of forward and inverse Gray code plus phase shifting stripe is researched.Based on the structured light 3D measurement simulation system,the researched method conduct simulation measurement experiment of the standard plane,the head statue with complex surface shape and two isolated objects composed of a ball and a teapot.The simulation experimental results show that the proposed method has the ability to eliminate the phase unwrapping error.In addition,in order to verify the antiinterference ability of the researched method,the researched method and the typical three-frequency heterodyne phase unwrapping method are used to carry out antiinterference measurement experiments on the plane and the head statue respectively.The experimental results show that the three-dimensional measurement method of forward and inverse Gray code plus phase shift studied in this dissertation has stronger anti-interference ability than the three-frequency heterodyne phase unwrapping method.Finally,the actual structured light 3D measurement system is built,and the system parameters are calibrated.Based on the built system,the traditional 3D measurement method of gray code plus phase shifting stripe and the studied 3D measurement method of forward and inverse gray code plus phase shifting stripe are used to carry out actual measurement comparison experiments for gypsum board,gypsum pyramid and plastic face.The experimental results are analyzed and quantitatively evaluated.The actual experimental results further show that the researched method can eliminate the phase unwrapping error,improve the accuracy of 3D measurement and improve the effect of 3D reconstruction.