| Among various optical 3D measurement methods,the grating projection 3D measurement method has the advantages of high precision,fast measurement speed and large amount of date measured in a single time.In the domestic avivation,aerospace,automobile and other manufacturing fields,the measurement of complex structural parameters mostly uses the raster projection 3D scanning measurement technology.Most of the high-precision grating projection 3D measurement equipment is imported equipment,and the measurement accuracy of domestic related products is relatively poor.Carrying out key technology research on high-precision grating projection measurement system can improve the independent controllability of domestic grating projection measurement technology and better serve highend manufacturing field.By studying the algorithm of raster projection scanning,this paper will improve the fringe phase calculation,system parameter calibration and non-sinusoidal error correction,so as to improve the measurement accuracy of raster projection scanning.The specific research work includes the following parts:(1)This paper compares and analyzes various phase unwrapping methods,and finds that three-frequency four-step is the most efficient and widely used method at present.The more the number of projected grating fringe images,the higher the accuracy of this method.Therefore,this paper improves the three-frequency four-step phase shift method.In order to reduce the number of projected raster images and speed up the measurement speed without reducing the accuracy,the three-frequency asynchronous phase shift method is obtained after optimizing the algorithm.Through multiple sets of simulations and experiments,measurement experiments are carried out on the surface of planes and spheres.Different gratings are projected onto the surface of the plane and sphere,and the phase unwrapping is carried out using various phase unwrapping methods and the optimized three-frequency asynchronous method.The results prove the feasibility and superiority of the three-frequency asynchronous phase shift method.(2)This paper combines the characteristics of binocular vision and grating projection 3D measurement technology and proposes a new projector calibration method.This calibration method is simple and easy to operate and has less constraints.Moreover,it can ensure high measurement accuracy,and is suitable for on-site calibration of grating projection threedimensional measurement technology.Finally,the feasibility of this calibration method is verified through experiments,and the reprojection error is 0.07 pexils,which shows that the calibration method is not only simple and easy to operate,but also has high calibration accuracy.(3)Combining the active error correction method and the passive error correction method,this paper proposes an efficient and easy-to-operate error self-correction method.The grayscale response is used for preliminary correction,and the phase mapping relationship is used for self-correction,which improves the effect of phase error correction.Finally,the effectiveness and superiority of this method are proved by experiments.(4)Build a complete grating projection measurement system and analyze the measurement effect of the algorithm in this paper.The effectiveness and superiority of the algorithm are proved by measuring standard device experiments.The repeatability and uncertainty of the measurement system were analyzed by several sets of experiments.The results show that the measurement accuracy of the grating projection measurement system using the algorithm in this paper reaches 12?m,and the research effect reaches the domestic advanced level. |
