Study On The Microscopic Fringe Projection System And Measurement Method

With the rapid development of micro-nano technology in recent years, a variety of high precision micro-components have been used widely, and this demands more for measurement technology. Traditional methods have been unable to satisfy the requirements of these new devices testing, so newer and better methods to achieve this purpose are needed. Three-dimensional measurement which combines fringe projection technique and microscopy is put forward for these demands. The mainly achievements in this dissertation are lists as follows:1. The literatures about microscopic measurement system at home and abroad were read, the current situation of fringe projection measurement techniques was investigated, and microscopic fringe projection system and method was chosen to measure the 3-D profile of micro-components.2. The principle of phase shifting technique to measure the 3-D profile of object was studied. Firstly, phase extraction and phase unwrapping algorithm have been analyzed. The five-step phase shifting method was proposed for the phase extraction, and residue removal algorithm used for phase unwrapping was applied.3. The measurement system was built up. The hardware of the system included the following modules: optical projection module, optical imaging module and image acquisition module. The software of the system mainly included the following parts: generating sinusoidal fringe, image acquiring&storing modules programmed by Labview, and phase extraction module, phase unwrapping module, system calibration module, generating object profile module programmed by Matlab.4. System calibration. Two methods were proposed to calibrate the system: projecting uniform fringe, for that the effective wavelength is a variable, all points in the measurement space should be calibrated; projecting deformation fringe, this time the effective wavelength is a constant, it can be obtained by calibrating just one point. In this dissertation, the z-axis of the system has been calibrated using the first method and the calibration result was verified by the experiments.5. At last, the micro-components have been measured by this system. To begin with, the repeatability, precision and other performances of the system were tested by the five-step phase shifting method and a ceramics plane board. The measurement system reached millimeter range and micro-level accuracy. Finally, a coin surface was measured to show the applicability of the system.