Research On 3D Shape Measurement Using Digital Moire Technique

Moire fringe 3d shape measurement technology is a structured light profilometry measurement method which can quantify the 3d shape of the object surface.Due to its advantages of non-contact,fast speed,full-field measurement and high resolution,it is currently widely used in industry inspection,robot vision,quality control,biomedicine and other fields.The basic principle of this technique is to superimpose the reference fringe and the deformed fringe modulated by the height of the object to be measured to form the moire fringe,and to analyze the moire contour by triangulation to obtain the real height information of the object.In order to realize accurate measurement of 3d objects and reduce image processing time,the method of digital synthesis of Moire fringes is used in this paper.When measuring an object,only one deformed fringe is collected.By digitally shifting the reference fringe obtained in advance and superimposing the deformed fringe to form a moire fringe,and the original high-frequency fringe is filtered by a simple Butterworth low-pass filter to obtain a clear moire contour map.In this paper,the three-step phase shift method is used to extract the phase information of the moire fringe,and the folded phase image is unwrapped by an algorithm based on the sorting of phase value boundary reliability and mask to obtain a high-quality continuous phase map distribution.In order to further obtain the real 3d information of the object,this paper gives a complete description of the calibration method based on the reference surface coefficient matrix,including mathematical model establishment,mapping equation derivation,coefficient calibration and experimental verification.The 3d object is reconstructed using the mapping equation after calibration,and the measured peak height error is only 0.19%,which has high measurement accuracy and resolution.This method does not require complex physical measurement of system parameters,avoids errors introduced by artificial measurement,and the method of coefficient calibration is simple and convenient,which is a feasible experimental scheme.