Study On Multi-frequency Phase Unwrapping And Highlight Suppression Method In 3D Measurement Of Stripe-Stucture Light

Three-dimensional measurement technology by coded structure light has been widely applied and developed in high-speed detection,product development,quality control,reverse engineering and other fields with its high accuracy,high efficiency and non-contact advantages.The measurement accuracy increases significantly with the development of hardware devices and image processing technologies.However,for complex objects tested,its fault tolerance and antiinterference ability are weak,which limit its practicality.For this reason,this article studied three-dimensional measurement methods of commonly used multiwavelength stripe structured light,starting from the classic three-dimensional measurement method of multi-wavelength stripe structured light,and focusing on measurement error caused by the phase unwrapping methodand the influence of surface characteristics on complex measured objects.Firstly,concerning the problem of gross errors caused by the complexity the existing phase unwrapping algorithm,limited range of expansion andwavelength position jumps,this paper proposedan optical phase unwrapping method with dual-frequency stripe structure a phase unwrapping method based on dualfrequency stripe structured light and established its mathematical model.Furthermore,according to the actual application environment,the error analysis of the proposed phase unwrapping method was conducted and its error margin was deduced.Through the three-dimensional measurement and verification experiments of anti-interference ability,the correctness of the dual-frequency phase unwrapping mathematical model and the error analysis were verified in a simulation environment with interference and without interference.Secondly,aiming at the existing multi-frequency mode time phase unwrapping methods,that is,multi-frequency stratification,multi-frequency heterodyne and multi-frequency theory,the explanation of measurement principle,measurement error analysis,numerical simulation experiment and the light phase unwrapping method of dual-frequency stripe structure were compared and studied.In view of the jump error of the start and end points of the projected pattern,an optical phase unwrapping method with dislocation double-band fringe structure was proposed to complete its theoretical analysis and numerical simulationverification.Thirdly,in order to further expand the coded light range or increase the antiinterference ability of the phase unwrapping method in the same range,the dualfrequency phase unwrapping method was extended to the tri-frequency phase unwrapping method.The mathematical model was established using trifrequencyphase unwrapping method as an example,the error analysis of the proposed phase unwrapping method was carried out,and its error margin was deduced.The equivalent wavelength of stripe structure light combination was analyzed,and the combination criterion of optimal frequency was put forward.Through the three-dimensional measurement and verification experiments of anti-interference ability,in the simulation environment with interference and without interference,the correctness of the mathematical model of the trifrequency phase unwrapping and its error analysis and the effectiveness in terms of error and anti-interference ability were verified.Fourthly,aiming at the measurement failure in the highlight region during the stripe structure light measurement,a highlight suppression method based on linear diffuser was proposed.Irradiance of emergent ray and incident rayafter passing through the linear diffuser and radiant brightness expression of highlight point reflected light were deducted.The principle model of highlight suppression of linear diffuser based on radiation metrics was built up.In order to further eliminate the highlight region,due to the complex image segmentation problems of the existing spectral suppression algorithm,the theory of reflection component separation and image processing algorithm of strong reflective surface spectral suppression based on a combination of priority-based pixel-filling theory were raised.Finally,three-dimensional measurement of stripe structured light and highlight suppression devices wereproposed and realized,experiments on threedimensional measurement experiment for typical surfaces and complex surfaces were performed.Experiments show that the phase unwrapping method of dualfrequency and tri-band stripe structure light can effectively suppress the jump error,thus,the operation is simple,and the measurement efficiency is high.The highlight suppression experiment on objects based on the linear diffuser and based on the combination of the theory of reflection component separation and the priority pixel filling theory were performed.Three-dimensional reconstruction experiments and qualitative and quantitative analysis were performed on strongly reflective surface objects of different shapes and smoothness.This study provides a theoretical and experimental basis for the phase unwrapping of stripe structure light three-dimensional measurement and highlight suppression,and has practical significance for the promotion of engineering applications of stripe structure light three-dimensional measurement.