Research On System Calibration And Defocus For Fringe Projection Profilometry

In the field of precision machining,3D shape measurement technology is the key to precision quality control.Among them,the fringe projection profilometry is widely used in the manufacturing field due to its high measuring speed,high point cloud density and non-contact.This paper starts with the optical component calibration of the fringe projection profilometry system,and then analyzes the appropriate defocusing of the projector can improve the system accuracy.A method to determination and adjustment of optimal defocus level for fringe projection systems is proposed,which can enrich the theoretical system of projection optics and improve the application value of the fringe projection measurement system in the industrial field.The main research contents and results are listed as follows:1.This paper analyzes the optical model of the fringe projection profilometry system and models and calibrates the camera and projector.Focus on the classification of the calibration method of the projector: projector calibration method based on virtual mark points,projector calibration method based on phase-shifting technique and projector calibration method based on binocular vision.The principles and methods of each calibration method are summarized,the experiments are carried out and the calibration results are compared.The advantages and disadvantages of three calibration methods are analyzed,which has the certain guiding significance in the choice of projector calibration method.2.This paper presents a method to determination and adjustment of optimal defocus level for fringe projection systems.Projector appropriate defocus can improve system accuracy.The projector lens defocus can be modeled as a Gaussian low-pass filter.By simulation,the fringe pattern with the sampling and quantization error of the projector is defocused,and the optimum defocus level of the fringe pattern is determined so that the projected fringe pattern is closer to the sinusoidal function.Then,the optimal defocus degree obtained by simulation is verified by experiments,and the special pattern is designed to adjust the degree of defocus.A method is proposed to adjust the projector to make the projected pattern in the optimal defocus degree.The results show the feasibility and validity of the proposed method,and the accuracy is improved up to 9.9% compared with the focus projected pattern.