Research And Error Analysis Of 3D Reconstruction Method Based On Color Structured Light

With the rapid development and increasing demand of modern manufacturing industry,which has gradually changed to high efficiency and intelligence.Thus,more accurate and efficient 3D measurement technology is urgently needed.As an important branch of non-contact 3D measurement,optical 3D measurement technology is widely used in the field of industrial measurement.The color structured light coding method carries a large amount of information,and only a few patterns are needed to obtain 3D morphology information.Because of its high resolution,faster measurement speed and other advantages,it has become a research focus of 3D structural light measurement.Based on color phase-encoded structured light,this paper combines the traditional phase shift method and multi-frequency heterodyne method to make 3D measurement.The theoretical analysis and compensation algorithms for the errors in the 3D measurement of color structured light are also carried out.Based on the color phase-encoded structured light,this paper introduces the phase-shifting principle,phase unwrapping algorithm and depth calculation method in detail.In the phase unwrapping,the multi frequency heterodyne principle is used to select the reasonable fringe coding frequency,and the improved phase unwrapping algorithm is introduced.Next,the reconstruction process from 2D color pattern to one point in 3D space is discussed.The principle of coordinate transformation and the mapping relationship between absolute phase and 3D coordinates are analyzed in detail.The problems of color crosstalk and Gamma distortion in structured light with color phase coding are studied.Through the derivation and analysis in the actual measurement process,the specific manifestations of the color crosstalk problem and the Gamma distortion problem are developed.We conclude the characteristics of the crosstalk between channels and the periodic error of Gamma distortion.Their effects on phase error and surface accuracy of 3D reconstruction are shown.In this paper,an inverse error compensation algorithm based on color phase-encoded structural light is proposed to solve the problem of Gamma distortion.The phase error of the Gamma distortion model is analyzed to show periodic fluctuations.According to the principle of reverse error compensation,an additional color fringe pattern is projected to offset the Gamma error.The effectiveness of the error compensation algorithm is verified by simulation analysis and experiments.Aiming at the problem of color crosstalk,a color crosstalk compensation algorithm based on point-to-point full field of view is proposed.The conversion relationship between camera pixel coordinates and projector pixel coordinates is used to construct an error compensation matrix on the projection plane to compensate point-by-point errors caused by color crosstalk.Finally,we based on the theoretical analysis to set up a color structured light experimental system.The accuracy of 3D reconstruction of color structured light before and after color crosstalk compensation is compared and analyzed,which proves the effectiveness of this method to improve the reconstruction accuracy.