基于小波变换条纹修补和条纹自相似性干涉条纹极值提取

提出了基于小波变换的条纹修补方法和利用干涉条纹自相似性的条纹灰度极值自动判读方法基于小波变换的条纹修补方法包括滤除噪音、多尺度小波变换、模极大值检测滤除奇异区域、近似信号自动修补,在此基础上进行多项式拟合,首先实现最外层条纹灰度极值的自动提取基于干涉条纹自相似性的条纹灰度极值自动判读方法是通过逐渐平移拟合区域,准确地提取了内层条纹的灰度极值位置,从而可以处理整幅图片的干涉条纹.此方法的特点是自适应、无需人为设定参量、处理速度快实验结果表明,该方法有很好的可靠性和准确性,并且处理区域大、用时少,仅需对图片扫描一次即可提取全部条纹的灰度极值.     

基于小波变换的干涉光谱信号检测与校正方法

傅里叶变换光谱仪通过获取待测光的干涉信号来反演光谱信息,是重要的光谱测试与分析仪器。受光电探测电路不稳定、干涉模块装调不到位等因素的影响,傅里叶变换光谱仪获得的干涉光谱信号会出现漏采点、过饱和点、噪声点等无效数据点,导致反演的光谱信号出现失真。为此,研究了一种基于小波变换的干涉光谱信号检测方法,该方法能够快速有效地定位干涉信号中多种无效数据点的位置;在此基础上,研究了干涉光谱信号的校正方法,根据无效点所在区间段的信号特征,通过样条插值方法进行数据拟合,校正干涉光谱信号。通过仿真验证了本方法的可行性;搭建了近红外波段傅里叶变换光谱实验系统,并基于该系统进行验证性实验,对获得的干涉信号进行检测与校正,提高了反演光谱信号的准确性。     

基于二维连续小波变换的ESPI条纹图相位提取方法

提出了一种基于二维连续小波变换的电子散斑干涉(ESPI)条纹图相位提取方法。通过检测二维小波脊确定条纹相位,并引入条纹频率作为向导,有效地避免了相位解调过程中的符号奇异性问题,从而使该算法既能处理开条纹图也能处理闭条纹图,且对散斑噪声具有较强的抑制能力。数值模拟和实验结果表明,该方法在抑制散斑噪声的同时能够有效地提取出条纹相位,对开条纹图和闭条纹图都能处理。     

基于希尔伯特变换的干涉条纹相位解调新算法

提出了一种新的应用希尔伯特变换解调干涉条纹相位的算法,可以从单幅干涉条纹图中解调出全场相位分布.在实际应用中,常借助傅里叶变换实现希尔伯特变换算法,但是会忽略负频率成分,造成相位信息的丢失.对于相位分布非单调变化的干涉条纹,提出了一种判断函数,用来计算相位信息零频率点的分布.利用相位的零频率点分布构造了一个二元模板,使用该模板对本文提出的两次希尔伯特变换法产生的包裹相位图进行修正.对修正后的包裹相位图进行解包裹处理,可以得到连续的全场相位分布.对该方法用计算机模拟进行了验证.     

基于小波变换的干涉图压缩算法

在研究小波变换和分层树集合分割排序算法的基础上,将小波图像压缩技术应用于干涉图的压缩.根据小波分解系数矩阵中高频子图像上数据接近于零,信息主要表现部分在低频子图像上,以及干涉图数据中主要信息集中在零光程差附近的特征,将干涉图一行数据拆开并按对角Z型排列存储为矩阵形式,再进行小波压缩.结果表明,此改进能提高压缩性能.     

基于希尔伯特变换的干涉条纹相位解调新算法

提出了一种新的应用希尔伯特变换解调干涉条纹相位的算法,可以从单幅干涉条纹图中解调出全场相位分布.在实际应用中,常借助傅里叶变换实现希尔伯特变换算法,但是会忽略负频率成分,造成相位信息的丢失.对于相位分布非单调变化的干涉条纹,提出了一种判断函数,用来计算相位信息零频率点的分布.利用相位的零频率点分布构造了一个二元模板,使用该模板对本文提出的两次希尔伯特变换法产生的包裹相位图进行修正.对修正后的包裹相位图进行解包裹处理,可以得到连续的全场相位分布.对该方法用计算机模拟进行了验证.     

静态傅里叶变换光谱仪的机理及干涉条纹的校正

针对高速、瞬时光谱测量要求光谱仪的结构简单、装备方便、实时性强的特点,文章介绍了一种静态傅里叶变换光谱仪,并对其原理进行了推导与剖析。针对其调整中出现的干涉条纹的倾斜校正问题,进行了详细的理论分析和干涉条纹模型的数学推导,得出倾斜镜旋转参数和光学元件最小通光口径之间的数学关系,以及倾斜镜旋转参数和干涉条纹旋转参数之间的数学关系。通过利用Matlab7.0数学工具,对所总结推导的干涉条纹模型进行模拟,对所得的各种参数之间的数学关系进行验证。分析结果表明据此数学关系所求得的β角校正精度达到1.4%,是一种有效可行的校正方法。     

动态干涉条纹相位提取的抗干扰算法

为减小在动态干涉条纹的相位提取中噪声带来的计数误差,研究了在希尔伯特变换相位提取的基础上,利用反正切相位跳变特性,通过软件实现可逆计数的抗干扰算法。通过模拟实验对算法的抗干扰性能进行了验证,实验结果表明：所提出的相位提取算法具有较强的抗干扰性能,在信噪比为11时,算法仍然能得到正确的结果。     

基于Hough变换的数字全息干涉条纹检测

提出了一种利用Hough变换在图像中检测模糊直线条纹的有效方法.将Hough变换对随机噪音不敏感的特性与Fourier变换的性质相结合,可实现对图形中有相同周期条纹的检测.该方法不针对单一条纹,只识别相同周期条纹的总体特征,能有效避免条纹部分缺失对检测结果的影响,并能快速检测条纹的准确数量.将该方法应用于数字全息干涉图的自动判读,成功实现全息干涉条纹的自动识别和准确计数,不仅避免了图像中条纹灰度不均匀、严重模糊的影响,而且提高了数字全息干涉术的测试准确度和效率.     

基于遗传算法的干涉条纹数据处理方法

提出了基于遗传算法的干涉条纹数据处理方法。该方法是在最小二乘余弦曲线拟合的基础上 ,引入了具有全局优化能力的遗传算法以解决目标函数多极值问题 ,从而使得最小二乘余弦曲线拟合对干涉条纹处理具有很好的鲁棒性和自适应能力。仿真结果表明 ,在 2 0 %均匀分布噪声条件下 ,拟合模型主要参数 -干涉条纹空间频率及初相位 -拟合误差小于 0 .5 %。     

Observation of Gouy phase anomaly with an interferometer

The intensity variation of bright and dark fringes in Young's double slit experiment shows that a light beam propagating through the focus of a lens experiences a phase shift (called the Gouy phase shift [Gouy CR. Acad Sci Paris 1890;110:1251]) with respect to its plane wave counterpart. The additional phase change of π introduced on focusing the light beam and then further propagating it in one arm of the interferometer changes a bright fringe into a dark fringe and vice-versa. We have, thus, made direct visualization of the Gouy phase shift by a simple experiment.     

远距离环状干涉条纹形成的初步实验

 针对远距离激光干涉成像中条纹的形成进行了研究。分析了成像所需条纹的特点,表明干涉条纹成像系统的带宽决定于条纹的空间带宽。讨论了传统的迈克尔逊干涉仪结构在激光干涉成像中应用的不足之处,并在迈克尔逊干涉仪的基础上,提出一种变形的光路结构,用于在远距离上形成圆对称环状干涉条纹,同时报道了利用该变形结构在约50m的距离上观察到的条纹,表明了该光路结构的可行性。     

恒星光干涉仪主动镜偏转角的检测

采用激光干涉检测的方法,综合应用计算机控制、数字图像处理等技术对高精密仪器主动镜的偏转角进行了检测.设计了主动镜的光干涉CCD数字图像检测系统,推导出了干涉条纹与主动镜偏转角之间的对应数学关系式,对条纹图像进行了噪音分析和相应的预处理,在干涉条纹细化的基础上对每条干涉条纹采用最小二乘法进行直线拟合,得到条纹间的间距以及条纹的方向角,最终检测出主动镜X轴方向的偏转分辨率为0″.113,最大偏转角为56″.872,Y轴方向的偏转分辨率为0″.112,最大偏转角为49″.835,完成了主动镜偏转角的检测.     

Phase recovery from fringe patterns using the continuous wavelet transform

Interferometry is well established as an optical technique in which a measurand is encoded as the phase of a periodically varying intensity pattern. In view of the inherent accuracy of interferometry, many methods have been developed to retrieve the phase from images of the fringe pattern. Our focus in this paper is one such technique—the continuous wavelet transform (CWT). We begin by reviewing the CWT and the space–spatial–frequency localisation properties of wavelets. We show that a path which follows the maximum modulus of the CWT (the wavelet ridge) gives the instantaneous fringe frequency as a function of spatial displacement. The phase is automatically and trivially obtained, without discontinuities, by integration. Examples of practical wavelets are given and algorithms to isolate the wavelet ridge reviewed.     

恒星光干涉仪主动镜偏转角的检测

采用激光干涉检测的方法,综合应用计算机控制、数字图像处理等技术对高精密仪器主动镜的偏转角进行了检测.设计了主动镜的光干涉CCD数字图像检测系统,推导出了干涉条纹与主动镜偏转角之间的对应数学关系式,对条纹图像进行了噪音分析和相应的预处理,在干涉条纹细化的基础上对每条干涉条纹采用最小二乘法进行直线拟合,得到条纹间的间距以及条纹的方向角,最终检测出主动镜X轴方向的偏转分辨率为0″.113,最大偏转角为56″.872,Y轴方向的偏转分辨率为0″.112,最大偏转角为49″.835,完成了主动镜偏转角的检测.     

Interference of circularly polarized light: contrast and application in fabrication of three-dimensional periodic microstructures

The contrast of interference pattern formed by two circularly polarized waves and by a linearly polarized wave and a circularly polarized one is discussed. The results are compared with that by two linear beams. It shows that the use of circular light in holographic fabrication of three-dimensional periodic microstructures may remove the necessity of beam ratio and polarization optimization needed in the interference of three linear noncoplanar beams and improve the uniform contrast of resultant pattern simultaneously.     

Unstable resonator alignment based on the fringe analysis

The existing cavity mirrors alignment method aligns cavities according to the symmetry of the near-field interference fringes of the guided lights by the unstable resonator. Its precision is restricted due to the lack of objective criterion for the fringe symmetry. This article proposes a high-precision cavity mirrors alignment method using the grey projection of fringe patterns as a solution to the problem. First, vertical and horizontal grey projection on the concerned fringe patterns; then an evaluation function for the cavity mirrors alignment is established using the distances between peak/valley values of all the levels in the projection curve as variables; finally, the function value is employed to characterize the fringe symmetry and thus to provide an objective criterion for the alignment effect of the stable resonator cavity mirrors. Experiments show that the proposed method is able to give effective evaluation for the symmetry of the near-field interference fringes of the guided lights and improve the alignment precision greatly.     

Improvement for optical mechanics method of coherent gradient sensing

Coherent gradient sensing (CGS) is double grating lateral-shearing interferometric technique with the simplicity of the optical set-up, non-contact, real-time, full-field optical information and variable resolution, which has shown many applications in the study of quasi-static as well as dynamic crack-tip field in both homogeneous and composite materials. It can be used both in a reflection mode (for opaque materials) and in a transmission mode (for transparent materials). The accuracy of the fringe order in the CGS interference image will deeply influence the precision of experimental study. Because of the difference in the optical principle from other optical methods, the fringe order of CGS cannot be obtained through the phase-shift technology. In this paper, a kind of modified CGS method is introduced and analyzed, which can accurately obtain the fringe order of random position in the CGS interference image. This method does not need additional optical set-up and complicated image processing techniques, but only needs several (greater than two) CGS interference images under different loadings. Static fracture experiments show that this method can evidently improve the precision of the CGS method.     

General representation of interference contrast formed by arbitrarily polarized waves and its application in wave design for holographic fabrication of photonic crystals

A general formula of interference contrast formed by two arbitrarily polarized elliptical waves propagating along arbitrary directions in three-dimensional (3-D) space is derived. From it a series of inferences for the interference of linear and circular waves including their different combinations are obtained. These formulae are used for polarization optimization in three and four noncoplanar beam interference for the fabrication of 3-D periodic microstructures. The numerical calculations show that the use of circular light can improve the uniform contrast considerably compared with the use of only linear light, and the use of elliptical light may make the contrast even higher.