Study On The Dynamic Testing Methods And System Of MEMS Based On Microscopic Interferometry

A key purpose for testing MEMS is to provide data feedback of measurements for every stage in the process of scientific research and product development, where MEMS devices' three-dimensional motions characterization is a very important aspect. A dynamic testing system based on microscopic interferometry and controlled by computer is developed, which is used to test the out-of-plane motions of movable MEMS components with nanometer resolution. This dissertation's main work is as following: 1. The techniques of interferometric fringe automatic analysis are discussed. The temporal phase-shifting interferometry with high accuracy is introduced and developed, aiming at three core algorithms, including phase-shifting algorithm, phase-unwrapping algorithm and image preprocessing algorithm. The error sources, which influence the phase extracting accuracy, are analyzed in detail. And the solutions are presented respectively. 2. Domestic/foreign static and dynamic testing techniques of MEMS are analyzed systematically. A dynamic testing platform is built up according to the modularized design based on the virtual instruments concept, integrated with optical, mechanical, electronical and computer technology. It has many excellent features, such as high precision, high speed, non-contact measurement in a large range, good expandability, high versatility, easy operation and flexible configuration. A stroboscopic drive circuit and a high-voltage amplifier circuit are designed and debugged, in order to realize stroboscopic illumination and high-voltage electrostatic stimulation of MEMS devices. A method of synchronization control between LED stroboscopic illumination and stimulation of MEMS devices is put forward, where software delay compensation is processed, with the result that the system can achieve high precision and broadband MEMS dynamic testing. 3. The phase-shift technology is applied to monochromatic light interferometry measurement, time-average interferometry measurement and white-light vertical scanning interferometry measurement respectively. By this way, phase information of interferometric fringe can be modulated, which is used in the analysis of MEMS dynamic behaviors. 4. A very important parameter, fringe contrast, is proposed, which can be used in analysis such as image-quality, phase-shifting algorithm, the local phase-unwrapping algorithm and global phase-unwrapping algorithm using weighted least-square method. Appling its variation, the system can measure the out-of-plane motions of MEMS devices with time-average interferometry method and white-light vertical scanning interferometry method. 5. In MEMS out-of-plane motion measurement, the two-direction phase-unwrapping method based on time axis and space axis is demonstrated. And the time and space information of MEMS motions are combined in favor of analyzing MEMS dynamic behaviors. In addition, 3-D motions of MEMS devices can be measured by using the whole field rebuilding technology based on mask. 6. The differential measurement method of MEMS dynamic characterization is put forward. A fixed point on the tested device is chosen as a reference point. It can decrease the influence of the random noise resource on the dynamic measurement, and improve the precision and repeatability of the system.