High Dynamic Range Surface Three-Dimensional Measurement System Based On Encoded Structured Light

Structured light measurement techniques are simple and efficient as well as contactless compared to traditional measurement methods.Among the structured light measurement techniques,coded structured light has the advantages of fast and high accuracy compared with other structured light measurement methods,but its measurement results are closely related to the reflective properties of the measured object surface.In the measurement process,if the surface of the object to be measured has a high reflectivity,it will lead to exposure in some areas of the imaging,resulting in phase deviation,thus affecting the measurement accuracy.In this thesis,we design and implement a high dynamic range surface Three-dimensional measurement system based on coded structured light through the research of binocular stereo vision and coded structured light measurement technology,camera calibration technology,coding and decoding technology of structured light,phase based stereo matching technology and quantitative measurement technology of highly reflective object surface,which is of great significance for measuring highly reflective objects.The research is of great significance.First,the measurement model of binocular structured light is selected and analyzed in the process of Three-dimensional measurement of highly reflective objects,and the measurement principle is derived.By establishing the imaging principle of the ideal model of the camera,the conversion relationship between the image coordinate system and the world coordinate system was determined,as well as the analysis of the aberration model of the camera.The Zhang’s calibration method is used to jointly calibrate the two cameras to obtain the geometric parameters inside and outside the cameras,and to improve the matching efficiency of the system by stereo correction of the left and right images.Secondly,by introducing different structured light coding methods and analyzing the advantages and disadvantages of different structured light coding,multi-frequency external aberration is finally selected as the coding method of this system.By analyzing the nonlinear errors generated in the measurement process,the main causes of the errors are defined In addition,the reflection model of highly reflective objects is analyzed,and an adaptive multiple exposure algorithm is proposed based on the camera response curve.By calculating the images with different exposure times for fusion,the high dynamic range images are synthesized for decoding,and the complete Three-dimensional point cloud data is generated.Finally,this thesis completes the hardware platform construction and software visualization program design of the system to realize the measurement of highly reflective objects.Through the measurement of different highly reflective objects,the feasibility and accuracy of the high dynamic range surface Three-dimensional measurement system based on coded structured light proposed in this thesis are verified,and the accuracy can reach 0.15 mm in the Three-dimensional measurement of standard step modules.