Abstract
A micromachined electrostatically controlled deformable mirror has been applied to the fields of adaptive optics, such as focusing mirrors, rration compensation and wavefront correction. This device is usually composed of a circular membrane and an electrostatic structure bonded underneath the membrane. The former acts as a reflective mirror while the latter provides an actuating force for controlling the curvature of the membrane. This paper presents a design methodology for the development of a deformable mirror. The static and dynamic performance of the electrostatically driven deformable mirror depends mainly on the depth of the gap, membrane structure, and electrode distribution. By assuming the deflection function and strain energy of the membrane, the nonlinear relation between driving voltage and static deflection of the membrane can be calculated. Both lumped model and energy method are employed to find the natural frequency of the membrane. To design a novel electrode for the focusing mirrors, the Ansoft Maxwell software has been used to analyze the uniformity of electrostatic field. In this research, surface micromachining is used for the fabrication of the lower electrode structure. This proposed fabricating process reduces the complexity of the traditional process. Having measured the surface profile and mechanical properties of the membrane, the static deflection and dynamic response of the actuator are investigated. Good agreement between computer simulation and experimental results indicates the correctness of mathematical model and the proposed energy method. Finally, the feasibility and applicability of the proposed methodology are discussed.