In this paper, we propose an instantaneous phase-stepping method for determining phase distribution of interference fringes utilizing a camera that is equipped with a micro-polarizer array on the sensor plane. An opti...In this paper, we propose an instantaneous phase-stepping method for determining phase distribution of interference fringes utilizing a camera that is equipped with a micro-polarizer array on the sensor plane. An optical setup of polarization interferometry using a Mach-Zehnder interferometer with two polarizers is constructed. Light emerging from the interferometer is recorded using a camera that has a micro-polarizer array. This micro-polarizer array has four different optical axes. That is, an image obtained by the camera contains four types of information corresponding to four different optical axes of the polarizer. The four images separated from the image recorded by the camera are reconstructed using gray level interpolation. Subsequently, the distributions of the Stokes parameters that represent the state of polarization are calculated from the four images. The phase distribution of the interference fringe pattern produced by the Mach-Zehnder interferometer is then obtained from these Stokes parameters, The effectiveness of the proposed method is demonstrated by measuring a static carrier pattern and time-variant fringe patterns. It is emphasized that this method is applicable to time-variant phenomena because multiple exposures are unnecessary for sufficient data acquisition in the completion of the phase analysis.展开更多
Viscous damping is a dominant source of energy dissipation in laterally oscillating micro-structures. In microresonators in which the characteristic dimensions are comparable to the dimensions of the fluid molecules, ...Viscous damping is a dominant source of energy dissipation in laterally oscillating micro-structures. In microresonators in which the characteristic dimensions are comparable to the dimensions of the fluid molecules, the assumption of the continuum fluid theory is no longer justified and the use of micro-polar fluid theory is indispensable. In this paper a mathematical model was presented in order to predict the viscous fluid damping in a laterally oscillating finger of a micro-resonator considering micro-polar fluid theory. The coupled governing partial differential equations of motion for the vibration of the finger and the micro-polar fluid field have been derived. Considering spin and no-spin boundary conditions, the related shape functions for the fluid field were presented. The obtained governing differential equations with time varying boundary conditions have been transformed to an enhanced form with homogenous boundary conditions and have been discretized using a Galerkin-based reduced order model. The effects of physical properties of the micro-polar fluid and geometrical parameters of the oscillating structure on the damping ratio of the system have been investigated.展开更多
分焦平面偏振探测系统受其探测器结构的影响,成像分辨率低于探测器实际分辨率,本文在不改变光学系统结构下使用微扫描获取亚像元微位移帧序列,提出一种改进的凸集投影(Projection On Convex Sets,POCS)算法用于提升偏振成像系统的成像...分焦平面偏振探测系统受其探测器结构的影响,成像分辨率低于探测器实际分辨率,本文在不改变光学系统结构下使用微扫描获取亚像元微位移帧序列,提出一种改进的凸集投影(Projection On Convex Sets,POCS)算法用于提升偏振成像系统的成像分辨率。该算法首先对获取到的偏振微扫描图像序列进行检偏角分离,将同组检偏角图像序列作为输入,其次进行位移匹配与凸集投影迭代初步重建高分辨率图像,然后将图像分组进行滑动窗口非邻域聚类,利用主成分分析将聚类后的图像进行降维,最后将每一维信息视为时间采样函数,在小波域进行软阈值降噪。实验表明,本算法可以有效的提高传统POCS算法的抗噪性能,提高分焦平面偏振探测系统的成像分辨率,和同类算法相比结构相似性系数提升0.02,峰值信噪比提升约1 dB,并且拥有更高的噪声鲁棒性。展开更多
文摘In this paper, we propose an instantaneous phase-stepping method for determining phase distribution of interference fringes utilizing a camera that is equipped with a micro-polarizer array on the sensor plane. An optical setup of polarization interferometry using a Mach-Zehnder interferometer with two polarizers is constructed. Light emerging from the interferometer is recorded using a camera that has a micro-polarizer array. This micro-polarizer array has four different optical axes. That is, an image obtained by the camera contains four types of information corresponding to four different optical axes of the polarizer. The four images separated from the image recorded by the camera are reconstructed using gray level interpolation. Subsequently, the distributions of the Stokes parameters that represent the state of polarization are calculated from the four images. The phase distribution of the interference fringe pattern produced by the Mach-Zehnder interferometer is then obtained from these Stokes parameters, The effectiveness of the proposed method is demonstrated by measuring a static carrier pattern and time-variant fringe patterns. It is emphasized that this method is applicable to time-variant phenomena because multiple exposures are unnecessary for sufficient data acquisition in the completion of the phase analysis.
文摘Viscous damping is a dominant source of energy dissipation in laterally oscillating micro-structures. In microresonators in which the characteristic dimensions are comparable to the dimensions of the fluid molecules, the assumption of the continuum fluid theory is no longer justified and the use of micro-polar fluid theory is indispensable. In this paper a mathematical model was presented in order to predict the viscous fluid damping in a laterally oscillating finger of a micro-resonator considering micro-polar fluid theory. The coupled governing partial differential equations of motion for the vibration of the finger and the micro-polar fluid field have been derived. Considering spin and no-spin boundary conditions, the related shape functions for the fluid field were presented. The obtained governing differential equations with time varying boundary conditions have been transformed to an enhanced form with homogenous boundary conditions and have been discretized using a Galerkin-based reduced order model. The effects of physical properties of the micro-polar fluid and geometrical parameters of the oscillating structure on the damping ratio of the system have been investigated.
文摘分焦平面偏振探测系统受其探测器结构的影响,成像分辨率低于探测器实际分辨率,本文在不改变光学系统结构下使用微扫描获取亚像元微位移帧序列,提出一种改进的凸集投影(Projection On Convex Sets,POCS)算法用于提升偏振成像系统的成像分辨率。该算法首先对获取到的偏振微扫描图像序列进行检偏角分离,将同组检偏角图像序列作为输入,其次进行位移匹配与凸集投影迭代初步重建高分辨率图像,然后将图像分组进行滑动窗口非邻域聚类,利用主成分分析将聚类后的图像进行降维,最后将每一维信息视为时间采样函数,在小波域进行软阈值降噪。实验表明,本算法可以有效的提高传统POCS算法的抗噪性能,提高分焦平面偏振探测系统的成像分辨率,和同类算法相比结构相似性系数提升0.02,峰值信噪比提升约1 dB,并且拥有更高的噪声鲁棒性。
