Research On Key Techniques Of Surface Morphology Measurement Based On Laser Interference Fringe

With the development of integrated circuits,manufacturing process,and materials research,the requirements for three-dimensional morphology measurement of surface are becoming increasingly demanding.Optical measurement integrates optics,electrotechnics,computer computing,and digital image processing technology.It has been widely studied and applied due to its non-contact,high precision,three-dimensional,rapid and real-time characteristics.In this thesis,the laser interference fringe has been applied to 3D morphology measurement of objects,which overcame the disadvantages of the traditional structured light type that the light is limited by the thickness degree of the grating and got dense interference fringes.This article focused on key techniques in phase measurement profilometry and Fourier transform profilometry,studied deeply the required digital image filtering,and obtained the 3D appearance of the measured objects.The experimental results showed that the proposed method based on laser interference fringe to obtain the 3D surface appearance of the object is feasible.The main research contents of this paper are as follows:1.The laser interference fringe array was realized according to the principle of shear interference.The system optical path was designed and the experimental platform was set up.To prepare for follow-up studies,both the stability of the fringes over time and spectrum characteristics were studied experimentally.2.Both the phase measurement profilometry and the Fourier transform profilometry were theoretically deduced and experimentally tested,and the 3D morphology of the measured for object surface was reduced,and the problems existing in the topographical reduction results were analyzed.Finally,the technical cores and application scenarios of the two methods were summarized.3.The principle of expansion for unwrapped phase was deduced,and the basic two-dimensional phase unwrapping algorithm has been improved to enhance correct rate of unwrapping operations under the premise of higher time efficiency.4.The digital image filters required in the project have been studied deepely.A method for determining the center position of the fundamental frequency,the selection width of the fundamental frequency,and the boundary between the DC component and the fundamental frequency has been given.By improving the one-dimensional discrete Fourier transform,a more detailed observation and processing of the frequency spectrum was achieved,and the bandpass filtering operation was further discussed.