Electrostatic actuators have been widely employed in optical MEMS and adaptive optics systems. Tri-electrode electrostatic actuators that possess a perforated intermediate electrode between the MEMS and an underlying primary electrode, have been developed to reduce the needed control voltage. This configuration has previously been shown to improve the controllable range of motion of the MEMS an additional 60 - 70 % compared to a conventional parallel plate actuator. In this paper, the effect of extending the size of the primary electrode beyond the width of the MEMS device is studied. The presence of the intermediate electrode provides partial isolation for the MEMS, and results in an electric field from the extended primary electrode reaching the top surface of the MEMS. This enables a lifting force that counteracts the attraction force from below, thereby increasing the actuator’s controllable travel range. This effect is dependent on the size of the MEMS with respect to the spacing from the intermediate electrode (D1). Finite Element Method (FEM) along with restoring spring force method (RSFM) are employed to study the actuator performance. The extended configuration is studied in a narrow MEMS device (with width 16D1) and a very narrow device (cantilever type width 6.5D1) to explore the travel range extension as a function of MEMS device size. The travel range before snap down of the narrow actuator with extended electrode showed an improvement of over 80% to that of a conventional electrostatic actuator, while the very narrow MEMS achieved 2.3 times more controllable travel distance.
A low-power three-degree-of-freedom scanning micromirror is presented. The 2- × 2-mm mirror is a gimbaless structure, directly supported by single-crystal microsprings. It is actuated by Lorentz force and is able to tilt about two axes and has linear motion in a third-axis. The transient and frequency responses of the micromirror are analyzed. The Lagrange’s equations of motions describing the dynamic behavior of the system are presented and show a good agreement with the experimental results. The fabricated microelectromechanical system mirror demonstrates a tilt angle of 22.8 deg at 247.5 Hz about y-axis, and 13.3 deg at 292.7 Hz about x-axis, in a 0.1 T magnetic field and 20-mA current on the mirror. Power consumption is 2.6 mW of power in tilting motions in resonant operation. With a total DC-drive current of 110 mA, 232-μm linear motion is achieved.
We report on an application specific integrated circuit (ASIC) drive electronics system being developed for integration with low-voltage (~20 V) microelectromechanical (MEMS) deformable mirror technology for next- generation adaptive optics instruments. The ASIC is designed and manufactured using a CMOS foundry to address the power consumption and signal routing complexity issues inherent to conventional drive electronics. A prototype 9-channel driver capable of producing a bipolar (±15 V) output signal has been designed and sent for fabrication. Simulation results and preliminary integration avenues for a fully packaged ASIC/MEMS device that exploit increasingly popular trends in the semiconductor industry will also be presented.
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