以垂直梳型致動器驅動之雙軸旋轉微鏡片之線性化

Abstract

微機電式微掃描鏡，已有諸多在光通訊、投影顯示、醫學影像等 的實際應用。靜電驅動式微掃描鏡由於靜電力矩與施加電壓的二次非線性效應，造成操作及控制上，必需輔以回授機制來校正非線性效應所造成的誤差。之前已有文獻針對於靜電驅動式平行板結構的微掃描鏡,利用差動電壓操作的方式來達到線性控制微掃描鏡。該操作方式是屬於開迴路式的驅動方式，既可以節省回授電路的功率消耗，亦可以減低微掃描鏡操作時，兩個互相垂直的旋轉軸之間的干擾。有別於平行板結構，我們針對靜電式垂直梳型結構的微掃描鏡，利用差動電壓對(Vx,Vy)疊加於直流偏壓(Vbias)，來驅動鏡面下的槓桿元件。首先我們以模擬來找出理想的直流偏壓工作點，並定義微掃描鏡的線性掃描範圍，再以實驗去觀察線性掃描範圍內的光點分布情形。在本實驗裡驗證了以差動電壓驅動來達到線性化操作的可行性。

MEMS (Micro-Electro-Mechanical Systems) scanners have been widely adopted in telecommunications, projection displays, and biomedical images. If we want to linearize the scanning field of a MEMS scanner, which is distorted by the intrinsic nonlinearity of the electrostatic torques, we must have an effective feedback mechanism to calibrate deviations.Several approaches have been proposed to suppress the scan pattern distortion of parallel-plate structure. Hiroshi et al. demonstrated the linearization of a two-axis parallel-plate MEMS scanner by using a differential-voltage driving scheme, which was relatively simple and was realized in open-loop operation. It not only reduces the power consumptions, but also suppresses the crosstalk of two orthogonal scan axes.A driving scheme using a pair of differential voltages (Vx, Vy) over a bias voltage is proposed to linearize the dc characterization (angle vs. voltage) of a two-axis MEMS scanner. The micromirror has a gimbal-less structure and is driven by vertical comb-drive actuators in conjunction with leverage mechanism.First of all, We find the optimize DC bias voltage form simulations by mathcad, and try to define the range of linear scanning fields. Second, Observing the distribution of laser light spots in linear scanning fields of different DC bias voltages. Finally the experimental results indicate that the differential voltage operation is effective to linearize the scanning field of lever-driven two-axis analog micromirrors.