Research On 3D Contour Measurement Algorithm Of Laser Interference Fringes

With the development of science and technology,people have higher and higher requirements for the accuracy of three-dimensional structure measurement of objects.In recent years,optical three-dimensional contour measurement has been widely studied and applied due to its non-contact,high precision,and low time consumption.In this paper,a precise measurement method of surface shape based on shear interference fringes is proposed,which utilizes the dense interference fringes generated by laser shear interference.It has the characteristics of simple,compact,stable and reliable structure,convenient and stable.At the same time,the software system including image acquisition,image processing and measurement result display was written,which made the whole measurement system perform surface precision measurement under the coordinated control of the operator and computer.The main research work of this thesis is divided into two parts,which respectively study the different three-dimensional contour measurement methods of large-area objects and small objects under dense interference fringes.For the measurement of the morphology of tiny objects:1.According to the principle of optical shear interference,the hardware platform of the measurement system used in the experiment was built,and the interference fringe characteristics generated by the measurement system were analyzed.2.The Fourier transform profilometry is used to measure the three-dimensional contour of the object.The Fourier transform profilometry is theoretically deduced and experimentally tested.The problems found in the experimental reduction results are studied and analyzed.Finally,the application scenario of the method is briefly introduced.3.The reason for generating the truncated phase is introduced,and the method of unfolding the truncated phase is studied.The one-dimensional phase unwrapping method is generalized to make it suitable for two-dimensional phase unwrapping.4.The reason for using image bandpass filtering is introduced,and the principle of image filtering is derived.The image filtering technique in this paper is deeply studied.The threshold selection method in image processing,the maximum inter-class variance method,is applied to the image filtering,so that the image filtering method used in this paper can adapt to complex practical use scenarios.Since the laser shearing interference used in Fourier transform profilometry produces a small area of interference fringes,it cannot be applied to realize three-dimensional contour measurement of large-area objects.Therefore,this paper studies camera calibration technology combined with computer.The technology has written automatic processing software.The high-accuracy experimental results have been obtained for the contour measurement of large objects,and the core algorithm of the three-dimensional contour measurement system for large objects has been completed.