In this work, deformation and focal length of a circular shape micro deformable mirror under different applying voltage is analyzed. This mirror has round shape. And it is circular clamped. In this work, the mirror is designed as MEMS (Micro-electro-mechanical systems) device. Therefore, it is considered to be fabricated by silicon-based micromachining. Such that, the material used as structure layer is silicon. And the metal layer is aluminum. For detail analysis of mirror shape deformed by electrostatic force, numerical simulation by finite element methods is used to analyze the deformation of mirror. Commercial software ANSYS is used as analyzing tool. For the symmetric shape of circular mirror, a 2D model is used as numerical mode. And theory of plates and shells is used to obtain theoretical solution. It is found that the numerical results agree with analytical results. Under the analysis, it is found the profile of mirror under applying voltage is parabolic. Therefore, it has good performance for focusing light. And from analysis, deformation of mirror is nonlinearly increases when the applying voltage being also increasing. Therefore, the focal length changes quickly under different applying voltage. From the results, it is found applying voltages are determined by the gap sizes between mirrors and lower electrodes. Pull-in voltage is also discussed. It is found the gap size has the most significant effect. However, the thicknesses of structure layer and metal layer have also important influence. From the results, the deformation and focal length of mirror under different applying voltage are determined by material properties and device sizes. And from theoretical solution of this work, relationships between applying voltage, material properties, and device sizes are obtained.
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