This study investigates seismic interferometry in which the Green＇s function is estimated between two receiv- ers by cross-correlation and integration over sources. For smoothly varying source strengths, the dominant...This study investigates seismic interferometry in which the Green＇s function is estimated between two receiv- ers by cross-correlation and integration over sources. For smoothly varying source strengths, the dominant contributions of the correlation integral come from the stationary phase directions in the forward and backward directions from the alignment of the two receivers. Gaussian beams can be used to evaluate the correlation integral and concentrate the amplitudes in a vicinity of the stationary phase regions instead of completely relying on phase interference. Several numerical examples are shown to illustrate how this process works. The use of Gaussian beams for the evaluation of the correlation integral results in stable estimates, and also provides physical insight into the estimation of the Green＇s function based on seismic interferometry.展开更多
In this paper, the out-of-plane deformation of silicon surface of Direct Chip Attachment (DCA) assembly, under thermal loading, was measured in real-time by Twyman/Green interferometry. The contour maps of the out-of-...In this paper, the out-of-plane deformation of silicon surface of Direct Chip Attachment (DCA) assembly, under thermal loading, was measured in real-time by Twyman/Green interferometry. The contour maps of the out-of-plane displacement fields of silicon surface under thermal loading and cycling of various temperature were obtained, Experimental results show that the relation between the out-of-plane displacement and temperature is nonlinear and varies with temperature cycling, due to nonlinear mechanical behavior of the materials used in electronic packaging. A comparison of the aut-of-plane displacement Gelds of silicon surface measured by T/G interferometry in real-time and replicating technique of high temperature specimen grating of moire interferometry was made.展开更多
The extraction of the Earth＇s Green＇s function from field fluctuations is a rapidly growing area of research. The principle of Green＇s function extraction is often related to the requirement of equipartitioning, wh...The extraction of the Earth＇s Green＇s function from field fluctuations is a rapidly growing area of research. The principle of Green＇s function extraction is often related to the requirement of equipartitioning, which stipulates that the energy of field fluctuations is distributed evenly in some sense. We show the meaning of equipartitioning for a variety of different formulations for Green＇s function retrieval. We show that equipartitioning is not a sufficient condition, and provide several examples that illustrate this point. We discuss the implications of lack of equipartitioning for various schemes for the reconstruction of the Green＇s function in seismology. The theory for Green＇s function extraction is usually based on a statistical theory that relies on ensemble averages. Since there is only one Earth, one usually replaces the ensemble average with a time average. We show that such a replacement only makes sense when attenuation is taken into account, and show how the theory for Green＇s function extraction for oscillating systems can be extended to incorporate attenuation.展开更多
针对用于太阳磁场精确测量的中红外观测系统(Accurate Infrared Magnetic field Measurements of the Sun,AIMS)望远镜8~10μm真空制冷成像终端系统的高精度装调需求,提出了一种基于中红外可调谐激光光源的宽谱段干涉检测和装调方法。首...针对用于太阳磁场精确测量的中红外观测系统(Accurate Infrared Magnetic field Measurements of the Sun,AIMS)望远镜8~10μm真空制冷成像终端系统的高精度装调需求,提出了一种基于中红外可调谐激光光源的宽谱段干涉检测和装调方法。首先,采用泰曼-格林干涉仪,利用参考臂可调的优势,弥补光源相干性不足的缺陷,从而实现8~10μm宽谱段的干涉测量。其次,完成了干涉仪光学系统设计,可同时兼顾8~10μm和可见光双波段的波前质量,解决了肉眼不可见给干涉仪自身装调带来的困难。设计结果表明,利用可见光激光器进行干涉仪自身装调,可达到RMS 0.05λ@0.633μm的波前精度;在8~10μm检测波段,干涉仪波前均方根优于0.001λ,可满足待测系统的检测需求。最后,基于逆向优化法仿真了8~10μm光学系统的装调流程。展开更多
Optical methods such as Twyman-Green interferometry, moiré interferometry, holographic interferometry and speckle interferometry are useful to measure displacement and strain in the full-field of structures. Rece...Optical methods such as Twyman-Green interferometry, moiré interferometry, holographic interferometry and speckle interferometry are useful to measure displacement and strain in the full-field of structures. Recently phase analysis method of fringe patterns obtained by these optical methods becomes popular, and it provides accurate quantitative results in the full-field. In this paper, in order to measure displacement and strain, real-time or high-speed nano-meter displacement measurement methods developed by the authors are introduced. That is, (1) out-of-plane displacement analysis by Twyman-Green interferometry using integrated phase-shifting method using Fourier transform phase-shifting method, (2) simultaneous two-dimensional in-plane displacement analysis by moiré interferometry and (3) out-of-plane displacement analysis by phase-shifting digital holographic interferometry. The theories and applications are shown.展开更多
基金supported by U.S. National Science Foundation EAR06-35611U.S. Air Force contract FA8718-08-C-002the members of the Geo-Mathematical Imaging Group (GMIG) at Purdue University
文摘This study investigates seismic interferometry in which the Green＇s function is estimated between two receiv- ers by cross-correlation and integration over sources. For smoothly varying source strengths, the dominant contributions of the correlation integral come from the stationary phase directions in the forward and backward directions from the alignment of the two receivers. Gaussian beams can be used to evaluate the correlation integral and concentrate the amplitudes in a vicinity of the stationary phase regions instead of completely relying on phase interference. Several numerical examples are shown to illustrate how this process works. The use of Gaussian beams for the evaluation of the correlation integral results in stable estimates, and also provides physical insight into the estimation of the Green＇s function based on seismic interferometry.
文摘In this paper, the out-of-plane deformation of silicon surface of Direct Chip Attachment (DCA) assembly, under thermal loading, was measured in real-time by Twyman/Green interferometry. The contour maps of the out-of-plane displacement fields of silicon surface under thermal loading and cycling of various temperature were obtained, Experimental results show that the relation between the out-of-plane displacement and temperature is nonlinear and varies with temperature cycling, due to nonlinear mechanical behavior of the materials used in electronic packaging. A comparison of the aut-of-plane displacement Gelds of silicon surface measured by T/G interferometry in real-time and replicating technique of high temperature specimen grating of moire interferometry was made.
文摘The extraction of the Earth＇s Green＇s function from field fluctuations is a rapidly growing area of research. The principle of Green＇s function extraction is often related to the requirement of equipartitioning, which stipulates that the energy of field fluctuations is distributed evenly in some sense. We show the meaning of equipartitioning for a variety of different formulations for Green＇s function retrieval. We show that equipartitioning is not a sufficient condition, and provide several examples that illustrate this point. We discuss the implications of lack of equipartitioning for various schemes for the reconstruction of the Green＇s function in seismology. The theory for Green＇s function extraction is usually based on a statistical theory that relies on ensemble averages. Since there is only one Earth, one usually replaces the ensemble average with a time average. We show that such a replacement only makes sense when attenuation is taken into account, and show how the theory for Green＇s function extraction for oscillating systems can be extended to incorporate attenuation.
基金The workis supported in part by DOE EPSCoR Program under contracts DE-FG02-01ER45899the Office of Fossil Energy,Advanced Research Materials ( ARM)Program,DOE,under contract DE-AC05-00OR22725 managed by UT-Battelle, LLC
文摘针对用于太阳磁场精确测量的中红外观测系统(Accurate Infrared Magnetic field Measurements of the Sun,AIMS)望远镜8~10μm真空制冷成像终端系统的高精度装调需求,提出了一种基于中红外可调谐激光光源的宽谱段干涉检测和装调方法。首先,采用泰曼-格林干涉仪,利用参考臂可调的优势,弥补光源相干性不足的缺陷,从而实现8~10μm宽谱段的干涉测量。其次,完成了干涉仪光学系统设计,可同时兼顾8~10μm和可见光双波段的波前质量,解决了肉眼不可见给干涉仪自身装调带来的困难。设计结果表明,利用可见光激光器进行干涉仪自身装调,可达到RMS 0.05λ@0.633μm的波前精度;在8~10μm检测波段,干涉仪波前均方根优于0.001λ,可满足待测系统的检测需求。最后,基于逆向优化法仿真了8~10μm光学系统的装调流程。
文摘Optical methods such as Twyman-Green interferometry, moiré interferometry, holographic interferometry and speckle interferometry are useful to measure displacement and strain in the full-field of structures. Recently phase analysis method of fringe patterns obtained by these optical methods becomes popular, and it provides accurate quantitative results in the full-field. In this paper, in order to measure displacement and strain, real-time or high-speed nano-meter displacement measurement methods developed by the authors are introduced. That is, (1) out-of-plane displacement analysis by Twyman-Green interferometry using integrated phase-shifting method using Fourier transform phase-shifting method, (2) simultaneous two-dimensional in-plane displacement analysis by moiré interferometry and (3) out-of-plane displacement analysis by phase-shifting digital holographic interferometry. The theories and applications are shown.
