MEMS微变形镜测试技术及算法研究

介绍了基于计算机控制的频闪显微干涉测量技术,实现了对MEMS微变形镜的表面形貌、离面变形、静态电压-位移曲线和谐振频率的测量。采用频闪成像、计算机微视觉技术以及基于最小二乘曲面拟合法的亚像素定位技术实现了对平面内微位移的测量;利用频闪成像以及5步相移干涉技术实现了对干涉相位的提取,建立了适合于MEMS微变形镜特性测试的相位解缠算法,恢复了代表被测物体表面形貌的真实相位,实现了微变形镜静动态特性的测试。测试结果表明:频闪显微相移干涉测量技术具有测量速度快、精度高、易实现自动控制等特点。     

MEMS变形反射镜主要特性测试

介绍了基于微机电系统技术的微变形反射镜的基本结构和电极分布.分析了微机系统变形镜的变形原理,推导了微变形镜的镜面变形与外加驱动电压的关系.分析了基于计算机控制的频闪显微干涉测量系统的组成及测试原理,并利用该系统实现了对微变形镜静态电压-位移曲线、静态面形、动态离面变形以及谐振频率的测试.实验表明,测试结果与理论分析有很好的一致性.     

MEMS变形反射镜主要特性测试

介绍了基于微机电系统技术的微变形反射镜的基本结构和电极分布.分析了微机系统变形镜的变形原理,推导了微变形镜的镜面变形与外加驱动电压的关系.分析了基于计算机控制的频闪显微干涉测量系统的组成及测试原理,并利用该系统实现了对微变形镜静态电压-位移曲线、静态面形、动态离面变形以及谐振频率的测试.实验表明,测试结果与理论分析有很好的一致性.     

利用Mirau显微干涉仪测量微器件的纳米级运动

描述了一种用于微机电系统（MEMS）纳米级微运动测量的Mirau显微干涉系统.该系统利用商业化的Mirau显微干涉仪，它直接安装在光学显微镜上，用于测量一个表面微加工水平谐振器的三维运动.面内运动取决于亮场在最佳焦平面处的图像，而离面运动则取决于频闪得到的干涉图像，该图像在物镜纳米定位器的8个不同位置处得到.实验结果表明了系统进行面内和离面运动测量的纳米级分辨力.     

基于单幅数字散斑投影及图像相关的离面振动测量

采用单幅数字散斑图投影及高速数字图像采集技术,研究了动态离面位移的测量。采用商用液晶投影仪将计算机产生的模拟散斑图投影到待测动态变形物体表面,由高速数字图像采集设备摄取并保存变形散斑图,采用时间序列数字图像相关软件计算出物体表面各点随时间变化的离面位移。这种方法用于振动分析时不仅可以获得振型分布,而且还可以获得各点的振幅值。与现有的激光频闪照相测振及激光多普勒测振等方法相比,具有光学系统简单,可全场定量测量。悬臂梁振动实验结果证实了该方法的有效性。     

一种即时平面标定的二维视觉测量方法

在二维视觉测量过程中,测量平面与标定平面的重合度是影响测量精度的重要因素。现有的二维视觉测量方法将平面标定过程及测量过程分步进行,测量平面与标定平面存在离面位移,通常需要精密的约束装置对标定靶标及待测物进行校准操作。为简化二维视觉测量过程并抑制离面位移,提出一种即时平面标定的二维视觉测量方法,通过在待测物上直接投射标定的激光点阵,建立待测平面与成像平面的映射关系,再根据该映射关系对待测物表面的特征点进行测量计算。该方法仅需对系统参数进行一次标定,与无离面误差校正的传统二维视觉测量方法相比,提高了测量精度,简化了测量过程。     

三维显微测振中离轴光路机械形变对耦合效率的影响

三维显微测振仪可用于测量微结构的三维振动,其两条离轴光路用于接收包含面内振动信息的信号光,系统的机械形变会直接影响光纤的耦合效率,从而影响系统的测振精度。结合衍射传播理论和光纤耦合原理,建立了离轴光路的信号光传输耦合模型,针对信号光平面与光纤平面存在倾角的问题,利用频域坐标旋转变换法将倾斜的物面信号光场投影到平行的参考平面上,再基于菲涅耳衍射传播计算得到光纤平面的光场分布,进而结合光纤的模场分布可计算得到光纤耦合效率。研究了耦合透镜、光纤等元件的机械形变对光纤耦合效率的影响,阐明了光纤耦合效率和各个机械变形量的关系,为三维激光多普勒显微测振系统的设计和装调工作提供了理论指导。     

双目视觉DIC测量系统的离面位移测量精度

采用离面位移测量精度达到10 nm~20 nm的电子散斑干涉测量系统验证了双目视觉数字散斑相关测量系统的离面位移测量精度。分别用电子散斑干涉测量系统和双目视觉数字散斑相关测量系统同时测量了平板离面位移,并对所测量的位移最大值进行了分析处理及比较。结果表明,双目视觉数字散斑相关测量系统的物体离面位移分布云图与电子散斑干涉测量系统的结果基本相同,且两者位移均方根相差为2.76 m~3.56 m,相对误差为4.59%~7.60%。因此,当被测量物体的离面位移大于4 m时,双目视觉Q400测量系统精度可达到电子散斑干涉测量系统的精度。     

基于激光差动多普勒效应的微机电系统动态测试技术

提出了一种用于测量微机电系统(MEMS)器件瞬时速度、位移的测量系统。采用激光差动多普勒技术,检测谐振器在平面内的振动,测量垂直于系统测量光轴方向的振动速度。并在差动多普勒测量光路的基础上加入了CCD监测光路,实时观察被测器件调整过程和振动情况。通过处理电路从光学系统输出的高频信号中提取多普勒信号,利用Labview和Matlab软件对采集的多普勒信号进行时频分析,得到被测器件的运动参量。通过对测点的微定位,对MEMS器件进行整平面的扫描,得到器件振动的瞬时速度场,为进一步对MEMS器件的高阶谱振动分析及扭转分析提供了一定的基础和必要的支持。     

MEMS动态测试系统及其数据处理

介绍了基于频闪显微干涉技术的MEMS动态测试系统的测量原理,设计了数据分析处理算法。采用基于立方插值的亚像素模板匹配技术实现了1/50像素的面内位移测量精度。利用分割线去包裹算法实现了从干涉图到三维形貌图的重构。     

Measuring in-plane and out-of-plane coupled motions of microstructures by stroboscopic microscopic interferometry

A stroboscopic Mirau microscopic interferometer system for measuring in-plane and out-of-plane periodic motions of microstructures is demonstrated. One full cycle of a periodic motion is divided into a number of motion phases. One sequence of interferograms with different phase shifting steps is collected at every motion phase by using stroboscopic imaging. A bright-field image can be extracted from one sequence of interferograms with the same motion phase. In-plane displacements are measured by applying an image matching method to all bright-field images, followed by a compensation for the relative positions of interferograms at the different motion phases, before calculating the phase distribution related to out-of-plane deformation. We demonstrate its capability for measuring a combination of out-of-plane deformation and in-plane displacement in a microresonator.     

Stroboscopic digital speckle pattern interferometry for vibration analysis of microsystem

In this paper, vibration measurement and analysis of microsystems, such as micro-electro-mechanical systems (MEMS) by using stroboscopic digital speckle pattern interferometry (DSPI) is presented. Because of the speckle interferometry, the technique is suited for samples which have a rough surface or whose surfaces can be sprayed into a scattering surface. A laser speckle microinterferometer incorporated with optoelectronic devices for a stroboscopic illumination and a synchronization of the signals between excitation and stroboscopic illumination is described and demonstrated. The system can measure both out-of-plane and in-plane displacement under either a static or dynamic loading. The fundamental is explained and some applications are demonstrated.     

Dynamic out-of-plane profilometry for nano-scale full-field characterization of MEMS using stroboscopic interferometry with novel signal deconvolution algorithm

A dynamic 3D nano-scale surface profilometer using stroboscopic white-light interferometry with novel signal deconvolution was developed to deliver dynamic surface profilometry with a measurement bandwidth of up to a MHz scale and a vertical resolution reaching 1 nm. Previous work using stroboscopic microscopic interferometry for dynamic characterization of micro-(opto)electromechanical systems (M(O)EMS) has been limited in measurement bandwidth of less than a few hundred kHz due to physical length limitation of stroboscopic light. For high-resonance mode analysis, the stroboscopic light pulse is too lengthy to capture the moving fringes from dynamic motion of the detected structure. In view of this need, a novel deconvolution algorithm using correction of the light response was developed for removing potential image blurs caused by the unavoidable vibration of the tested parts. With this advance in technology, the bandwidth of dynamic measurement can be significantly increased without sacrificing measurement accuracy. A microcantilever beam used in AFM was measured to verify the capability of the system in accurate characterization of dynamic behaviors of M(O)EMS.     

Sandwich-speckle hologram: A combined method for local displacement analysis

Sandwich hologram interferometry and sandwich speckle photography tend to complement each other as displacement measuring methods; a sandwich hologram is best suited for out-of-plane movements, while speckle photography is used to determine in-plane components. The two techniques can be combined and both holographic and speckle photographic data can be stored on the same sandwich pair. Fringes caused by in-plane rigid body motion can be compensated for and local displacement evaluated.     

Time-average hologram interferometry of periodic,non-cosinusoidal vibrations

In the present paper, the method of time-average hologram interferometry has been applied to study periodic, non-cosinusoidal vibrations represented by a Jacobian elliptic function. For such vibrations the characteristic fringe function has been evaluated by making use of an equation derived from considerations of the effect of motion on coherence. Techniques of holographic addition and subtraction and extended pulse stroboscopic holography have been applied to analyze these vibrations in detail. Graphical representation of the fringe irradiance distributions in the reconstructed image is given in all the cases.     

In-plane vibration characterization of microelectromechanical systems using acousto-optic modulated partially incoherent stroboscopic imaging

A technique using acousto-optic modulated partially incoherent stroboscopic imaging for measurement of in-plane motion of microelectromechanical systems (MEMS) is presented. Vibration measurement is allowed by using flashes of the partially incoherent light source to freeze the positions of the microstructure at 12 equally spaced phases of the vibration period. The first-order diffracted beam taken out by an acousto-optic modulator (AOM) from the light beam of a laser is made partially incoherent by a rotating diffuser and then serves as the stroboscopic light source. Both the MEMS excitation signal and the flash control signal are provided by a dual-channel function generator. The main advantage of this measurement method is the absence of a stroboscopic generator and a high speed digital camera. Microscale prototypes are fabricated and tested. Quantitative estimates of the harmonic responses of the prototypes are obtained from the recorded images. The results agree with those obtained with a commercial MEMS motion analyzer^TM with relative errors less than 2%.