Study On Micro-nano Measurement Technology Of Out-of-plane Deformation Using Laser Speckle

Laser speckle interferometry (also known as Electronic Speckle Pattern Interferometry, ESPI) is a non-contact optical non-destructive measurement method. It has been widely used in the measurement of displacement, deformation, stress and strain, surface roughness and vibration analysis of a variety of materials and structure with the high accuracy, high sensitivity and whole field fast measurement advantages. Laser speckle interferometry has also gradually been applied to micro-nano measurement (such as vibration and deformation analysis of MEMS devices). In this paper, the key technologies of speckle interferometry micro-nano measurement have been studied. And a laser speckle out of plane deformation measurement system has also been established, which include both the hardware and software part.Speckle interferometry measures physical quantities through the phase change, so an appropriate and accurate phase measurement method is of crucial importance. This paper studies the most commonly used phase shift method, which is also with high precision. And then apply it to the actual phase measurement in the experiment part. After that some filtering methods are introduced, like anisotropic diffusion filtering, adaptive weighted filtering and sine cosine phase filtering. In the simulation and practical application, these methods achieve good filtering result, which is that they can effectively maintain the useful information like fringe structures and phase jumps when filtering speckle noises. Finally, unwrapping techniques of the wrapped phase map are studied. The algorithm based on sorting by reliability following a non-continuous path and the algorithm based on image decomposition are both of great anti-noise ability, and can also effectively isolate the physical phase discontinuities to prevent interference while unwrapping. The latter achieves better performance in practice.The laser speckle out of plane deformation micro-nano measurement system has been designed and built base on phase shift method. The measurement software has also been developed using Visual C++ platform to integrate algorithms above. Then a center loaded metal disk is tested to get the micro out of plane deformation. And we obtain a relatively smooth whole filed deformation distribution, which demonstrates the effectiveness of the measurement system and related algorithms.