High Surface Quality Of Large-stroke Mems Micro Deformable Mirror Technology

The adaptive optical system is composed of the wavefront sensor, the wave front constructor and the wavefront corrector, which can correct the wavefront aberration distorted by atmospheric turbulence. Based on MicroElectroMechanical System (MEMS) technology, the micro deformable mirrors as the wavefront corrector offer the advantages in size, cost, weight, speed and integration. The elements of segmented micro deformable mirrors are separated and the distance between them is very small. The segmented micro deformable mirrors are easier to control and integrate, so they are the objects studied by this thesis.The performance needs of micro deformable mirrors required by the adaptive optical system are analyzed by this paper, which concludes the number of elements, the response frequency, the stroke, the filling factor and the quality of the surface. Under the condition of the certain array of the segmented micro deformable mirrors, the Opto-Elelctro-Mechnical characteristics are researched. The response speed of the micro deformable mirrors is rapid, which can meet the needs the of the real time modulation of the adaptive optical system. The distance between the upper and the down plates of the micro deformable mirrors fabricated by the MUMPs technology is the 2um.At the same time the mirrors are influenced by the pull in phenomenon, so the range of the wavelengths corrected by them is districted. So they can be only applied in the range of the visible and infrared light. The raised and depressed topography of the surface is due to the conformability of the film deposition in the MUMPs technology. Moreover the residual stress and the stress gradient of the structure are provided by the film deposition. So the surface quality of the mirrors is reduced.For the methods of increasing the stroke, the methods of capacitance in series with the mirror and the nonlinear elastic spring are discussed, the lever bending method and the electrostatic repulsive force method are introduced. Through the analysis of the method of capacitance in series with the mirrors, when the capacitance in series is the half of the initial of the capacitance of the mirror element, the stroke can achieve...