運用於垂直微鏡面驅動之非對稱間隙旋轉梳狀致動器

Asymmetric-gap Rotary Comb-drive Actuators for the Application of Vertical-Micromirror Actuation

涂清鎮(Ching-Chen Tu)

指導教授 ： 劉承賢

國立清華大學/工學院/動力機械工程學系/博士(2009年)

摘要

旋轉靜電梳狀致動器能夠以驅動單一垂直微鏡面來達到一對多通道的光切換功能。第一個旋轉梳狀致動器是田等人於1989所提出的，並且利用對稱間隙梳狀電極來產生靜電轉矩。對於光切換應用來說，微致動器的共振頻率是一個重要的動態特性規格。

本研究提出利用非對稱間隙（Asymmetric Gap）以及楔形頂針（Wedge-shaped Bearing）的致動器設計在不犧牲旋轉角度之下加強旋轉致動器本身的共振頻率。相較於傳統對稱間隙旋轉梳狀致動器而言，非對稱間隙旋轉梳狀致動器在相同操作電壓下可以產生較大的靜電轉矩。在我們的設計中，雖然操作電壓超過了吸附電壓（Pull-in Voltage），但非對稱間隙旋轉致動器仍可以利用楔形頂針旋轉而不會發生吸附行為（Pull-in Behavior）。並且利用具有中央樑（Middle Beam）設計的繞曲彈簧（Serpentine Flexure）在加強共振頻率的同時改變旋轉致動器的共振頻率模態。從非對稱間隙旋轉梳狀致動器的量測結果得到當直流操作電壓在已超過吸附電壓達107V情形下致動器仍可旋轉並且旋轉角度可以達到5°，而在交流操作電壓77V頻率為共振頻1.54 KHz時旋轉角度可以達到±5°。我們也提出設計與製造方法將垂直微鏡面製作在對稱間隙與非對稱間隙梳狀致動器之上，並且在論文中針對垂直微鏡面驅動的結果加以說明與討論。

關鍵字

光學微機電 ； 微光切換器 ； 垂直微鏡面 ； 旋轉致動器 ； 靜電梳狀致動器 ； 非對稱間隙

並列摘要

Rotary electrostatic comb-drive actuator can achieve the 1 × N channels optical switching by actuating a single vertical micromirror. The first rotary comb-drive actuator presented by Tang et al. in 1989 uses the symmetric-gap comb fingers to generate the electrostatic torque. For the applications of optical switching, resonant frequency of the microactuators is an important specification of the dynamic response.

This research proposes the actuator design which enhances the resonant frequency of the rotary actuator without scarifying the responding rotation angle via the asymmetric gap and the wedge-shaped bearing. Compared to classical symmetric-gap rotary comb-drive actuator, the asymmetric-gap rotary comb-drive actuator generates the larger electrostatic torque under the same actuating voltage. The asymmetric-gap rotary actuator can rotate itself without the pull-in behavior via the wedge-shaped bearing when the applied voltage is beyond the pull-in voltage in our design. The design of serpentine flexures with the middle beams is utilized in this study to support the restoring rotation of the asymmetric-gap rotary actuator, approach appropriate vibration modes as well as enhance the resonant frequency of desired rotational mode. A responding rotation angle of 5° at the DC applied voltage of 107 V beyond the pull-in voltage for a steady-state measurement and ±5° at the AC applied voltage of 77 V at the resonant frequency of 1.54 kHz were measured with our asymmetric-gap rotary actuators. We also propose the design and fabrication process to attach the vertical micromirror to our symmetric-gap and asymmetric-gap rotary comb-drive actuators. The vertical-micromirror actuations based on our symmetric-gap and asymmetric-gap rotary comb-drive actuators are demonstrated and characterized in this thesis.

並列關鍵字

Optical MEMS ； Optical Switch ； Veritcal Micromirror ； Rotary Actuator ； Electrostatic Comb Drive ； Asymmetric Gap

參考文獻

[1] S. V. Kartalopoulos, DWDM: Networks, Devices, and Technology, IEEE, 2002.

[2] T.-W. Yeow, K. L. E. Law, and A. Goldenberg, “MEMS Optical Switches,” IEEE Communications Magazine, pp.158-163, Nov., 2001.

[3] P. B. Chu, S.-S. Lee, and S. Park, “MEMS: The Path to Large Optical Crossconnects,” IEEE Communications Magazine, pp.80-87, Mar., 2002.

[4] S. Mechels, L. Muller, G. D. Morley, and D. Tillett, “1D MEMS-Based Wavelength Switching Subsystem,” IEEE Communications Magazine, pp. 88-94, Mar., 2003.

3D Optical Switches