Research On Techniques Of Dynamic 3D Profilometry Based On Fiber Optic Interferometric Projection

Three-dimensional profilometry plays an increasingly important role in the fields such as quality reliability, machine vision, medicine, archeology, automatic location and navigation, and becomes a significant content and method of scientific and technical research in medical instrument, optical instrument, and materials. Supported by the exploratory project of the State Key Laboratory of Precision Measuring Technology and Instruments and to aim at the 3D detection of optical parts in small sizes and the vibration of membrane in low frequency, this paper uses fiber optic to project interferometric fringes, improves the traditional Fourier Transform Profilometry (FTP), builds up the coordinate system. The images of deformed fringes are captured by camera, and filtered by 2D Fourier transform in frequency domain. After that, the phase can be detected and phase unwrapping is employed to reconstruct the 3D profile. On the base of former research, this thesis improves the system and parts of the method to provide basic study for a kind of dynamic 3D profilmetry. The main works are shown as follow:1) Put forward the measuring means of dynamic 3D profilmetry, constructed the measuring coordinates according to the structure of classical FTP, and raised the relationship between the coordinates of the points and the phase modulated by the object surface according to the pinhole model.2) To direct at solving the fringes drifting caused by the environment, designed a digital PID control system base on the principle of DC phase tracking, and increased the anti-vibration ability of the fiber interferometer effectively.3) To resolve the deficiency of existing methods to calibrate the systematic parameters, studied a few method and made experiments, simplified the calibration steps and raised the accuracy.4) Spin-filter, 2D Fourier transform, automatic rectangle window location in frequency domain, and 2D inverse Fourier transform were applied in deformed fringe pattern one by one to get the wrapped phase image. Phase unwrap was used with the systematic parameters to reconstruct the 3D profile of the object.5) Developed the application software with SDK of the camera in VC6.0, transplanted the image processing algorithms into the software, generated the dynamic link library of 3D show functions for VC6.0 with Matlab, and realized the automatic snap and process of the fringe pattern and the display of the 3D profile, that offered a possible way to dynamic measurement.