用于缺陷检测的圆环孔径锥镜剪切散斑干涉法

介绍了一种利用圆环孔径和锥镜剪切散斑干涉技术检测缺陷的新方法，该方法是一种非接触式的检测方法．不受缺陷形状和位置的影响，能够准确地检测出缺陷的位置和大小。分析了圆环孔径锥镜剪切散斑干涉的基本原理，给出了散斑图全场滤波分析的平均光强解析式和实验结果。结果表明，该方法能在一张双曝光的散斑图上可同时记录物体在所有方向上的变形信息，并能连续地再现出来，散斑图的信息量丰富。在全场滤波分析时，适当选择滤波孔的位置，可得到清晰的缺陷的全场条纹图。在实时滤波分析观察时，将滤波孔连续地旋转，可观察到物体动态变形的全过程，散斑图的条纹在变化，而缺陷的位置不变，从而为缺陷检测或其它动态检测方面提供了一种新方法。     

微粒空间运动轨迹测定的一种光学并行处理方法

介绍脱硫塔内离心喷雾雾场中雾粒沿塔体分布的测试结果，指出粒子的运动轨迹测试是一个国际上共同关心的问题，用双曝光散斑图的分析方法来分析微粒运动，其中介绍了双曝光散斑图的分析原理以及如何全息透镜阵列来分析颗粒在平面内的移动，从垂直两平面获取微粒运动的双曝光图，通过光学并行处理和图象的分析得到颗粒空间运动轨迹的可能性，文中还讨论了一些试验结果和尚待研究的问题。     

微粒空间运动轨迹测定的一种光学并行处理方法

介绍脱硫塔内离心喷雾雾场中雾粒沿塔体分布的测试结果，指出粒子的运动轨迹测试是一个国际上共同关心的问题。用双曝光散斑图的分析方法来分析微粒运动，其中介绍了双曝光散斑图的分析原理以及如何用全息透镜阵列来分析颗粒在平面内的移动，从垂直两平面获取微粒运动的双曝光图，通过光学并行处理和图象的分析得到颗粒空间运动轨迹的可能性。文中还讨论了一些试验结果和尚待研究的问题。     

电子错位散斑干涉系统中错位量的研究

电子错位散斑检测系统中,错位量对测量精度、灵敏度以及条纹对比度有很大影响。本文介绍了电子错位散斑干涉原理,研究了错位量与测量精度、灵敏度和条纹对比度之间的对应关系,并利用MATLAB模拟出不同错位量下干涉条纹图,将错位散斑模拟条纹图与理论分析有效结合,总结出选取错位量的方法,并将其应用于轮胎变形检测实验,取得了良好的实验效果。本文研究工作对无损检测中错位量定量选取具有实际指导意义。     

流体温度场测量中的电子散斑干涉技术

电子散斑干涉是一种利用全电子记录和计算机图象处理系统替代传统照相干版进行测量的先进技术。本文在简要介绍其应用于流体温度场测量的理论与实验的基础上,着重描述了如何通过调整光学系统参数配置来获取最佳质量原始干涉图象的途径,并给出对比分析结果。     

白光频闪散斑干涉术的研究

在利用白光对振动物体进行测量时,由于白光的相干性较差,难以得到质量较好的图像,为了克服这一缺点,本文提出了一种用白光光源照明进行振动测量的新方法-白光频闪散斑干涉术.阐述了白光频闪散斑干涉术的基本原理,分析了提高图象质量的主要原因,采用了相干性较好的白光光源和合理的光路,使系统的时间相干性和空间相干性得到提高,从而提高了图像的质量.实验结果表明,该方法用于振动的测量,能给出物体在任一瞬时的振动信息,得到清晰的、高对比度的全场干涉条纹图,图像的质量得到大大提高.     

孔径径向扫描白光散斑干涉法的研究

提出了一种用于动态研究的新方法-孔径径向扫描白光散斑干涉法,介绍了两孔和直三孔径向扫描器.该方法是一种非接触式的用于动态测量的白光散斑法.分析了孔径径向扫描白光散斑干涉法的基本原理,给出了白光散斑全场滤波分析的平均光强解析式和实验结果.该方法的优点是利用散斑的调频技术能在一张白光散斑图上记录物体的连续动态变形的信息,在全场滤波分时,能将物体动态变形的信息方便地提取出来,得到清晰的全场白光散斑条纹图.直三孔径向扫描法能得到物体在x方向、y方向和45°方向上的变形信息.在实时全场滤波分析观察时,将滤波孔连续地沿径向扫描,可观察到物体连续动态变形的全过程,从而为物体的动态研究提供了一种新方法.     

散斑干涉条纹图的总变分去噪方法

去除散斑条纹图中的噪声是电子散斑干涉测量技术的关键问题.提出将总变分图像去噪方法应用于电子散斑干涉条纹图滤波过程中,并对保真系数进行了改进.用总变分模型定义图像的能量函数,利用变分法求得满足能量函数的最优解,将图像去噪过程转化为求解偏微分方程的过程.分别对计算机模拟的条纹图和实验获得的条纹图进行了测试,定性和定量分析的结果表明该技术能够在显著滤波的同时保持条纹的对比度.     

用于测振的电子散斑剪切干涉术

电子散斑剪切干涉术作为一种高精度全场测量技术,已被广泛应用于无损检测(NDT)、应变分析、振动检测和流场分析等领域．主要分析了电子散斑剪切干涉术在振动检测领域的应用,分析了它利用时间平均法检测振动的原理,并为实现物面振动的大面积检测进行了电子散斑剪切干涉仪光学结构的参数设计,一次可以检测大小为669 mm×502mm的矩形物面．利用计算机模拟产生随机高斯相关表面的高度分布函数及振动散斑剪切条纹图．结果表明电子散斑剪切干涉术用于振动检测．     

散斑及其应用探究

散斑效应是信息光学的重要组成部分,现在,散斑效应的应用已经渗透到很多领域,主要通过对散斑效应的应用作初步的探讨,着重介绍散斑摄影术和散斑干涉计量术。     

Computer-aided speckle pattern interferometry

An on-line computer system for measuring the deformation of a diffuse object with a speckle interferometer is presented. Methods for evaluating a speckle interferogram using digital image processing techniques are also discussed. The system consists of an interferometric optical setup and a computer-TV image processing facility. A speckle interferogram is generated arithmetically between two digitized speckle patterns before and after deformation of the object. The information about the deformation is extracted by two procedures in analyzing the interferogram: (a) automatic analysis using digital image processing techniques such as gray scale modification, linear spatial filtering, thresholding, and skeletoning; (b) man-machine interactive method for simple high-speed processing of the interferogram using a light pen. The determined fringe order numbers are interpolated and differentiated spatially to give strain, slope, and bending moment of the deformed object. Some examples of processed patterns are presented.     

经验模态分解技术在SAR干涉图滤波中的应用

提出了一种基于经验模态分解技术的滤波算法。该算法可以把原始数据分解成不同尺度的信息,从初始于涉图上减去与斑点噪声所对应尺度的信息,就可以达到斑点噪声抑制的目的。与另外两种滤波算法进行比较的结果表明,该算法不仅能有效地去除斑点噪声,并且能很好地保持相位的细节信息和条纹的边缘信息,保持相位的纯洁性,而且大比例地减少了残余点的数量,更有利于相位解缠。     

基于静态小波分解的SAR干涉图滤波

在干涉图的表态分解小波域进行了中值滤波，并和另外3种滤波得法进行了比较。结果表明，该算法不仅能有效地去除斑点噪声，并能很好的保持相位的细节信息和条纹的边缘，保持相位的纯洁性，而且大大地减少了残余点的数量，更有利于相位解缠。     

High resolution speckle interferometry using virtual speckle pattern produced by information of deformation process

A high resolution new fringe analysis method for ESPI with only one camera is proposed by using features of speckle interferometry in a deformation process of a measured object. The profile of intensity of each speckle of the speckle patterns in the deformation process is analyzed by the Hilbert transform. A virtual speckle pattern for creating a carrier fringe image is produced artificially by using the information of profiles of intensities of speckles. The deformation map of the measured object can be detected by the virtual speckle pattern in an operation based on the spatial fringe analysis method. Experimental results show that the difference between the results by the new and the ordinary methods is 0.1 rad as standard deviation. From the results, it is confirmed that the high resolution measurement can be performed by this method the same as compared to the ordinary measurement method which needs to employ three speckle patterns.     

Binary Star Reconstruction with Use of the Blind Deconvolution Method

Abstract

The iterative blind deconvolution method and a modified auto-correlation method are applied to reconstruct a binary star from a speckle interferogram. The results of two methods are compared to evaluate reconstructed images. For successful reconstruction, a method of frame selection of speckle interferograms is also proposed. A suitable frame selection improves the efficiency of the reconstruction. Some results of the binary star reconstruction are demonstrated to show the usefulness of our method.     

气流场ESPI载频条纹图的消噪处理与相位提取方法

为拓展ESPI方法在流动可视化测量技术中的应用,对气流场ESPI载频条纹图进行了傅立叶变换、数字全低通滤波,和傅立叶逆变换的处理以消除散斑噪声,并直接将其替换为原散斑相关条纹图,进而成为保留了流场信息的高对比度、低噪声的灰度条纹图,便于提取原散斑图中流动相位信息。根据模拟数据确定了由这两种条纹图互换所引起的空间相移量和相应流场测量中的修正量。提出了用灰度扫描法对互换后的条纹图进行一维灰度扫描,由灰度计算得出气流扰动的一维相位差分布和流场一维温度分布;同时也用FTP法对该图进行了二维相位展开和温度分布计算,亦可对多帧条纹图进行时间轴上的逐点相位提取以计算其他流场参数。结果表明,计算数据与实测符合,方法简单易行,为在气流场参数测量中应用动态ESPI方法提供了一种实用有效的方法。     

Ultrasound speckle reduction using modified Gabor filters

B-mode ultrasound images are characterized by speckle artifact, which may make the interpretation of images difficult. One widely used method for ultrasound speckle reduction is the split spectrum processing (SSP), but the use of one-dimensional (1-D), narrow-band filters makes the resultant image experience a significant resolution loss. In order to overcome this critical drawback, we propose a novel method for speckle reduction in ultrasound medical imaging, which uses a bank of wideband 2-D directive filters, based on modified Gabor functions. Each filter is applied to the 2-D radio-frequency (RF) data, resulting in a B-mode image filtered in a given direction. The compounding of the filters outputs give rise to a final image in which speckle is reduced and the structure is enhanced. We have denoted this method as directive filtering (DF). Because the proposed filters have effectively the same bandwidth as the original image, it is possible to avoid the resolution loss caused by the use of narrow-band filters, as with SSP. The tests were carried out with both simulated and real clinical data. Using the signal-to-noise ratio (SNR) to quantify the amount of speckle of the ultrasound images, we have achieved an average SNR enhancement of 2.26 times with simulated data and 1.18 times with real clinical data.     

Control of phase of fringes in speckle interferometry for application of fringe scanning method

The speckle interferometry is an effective technique in the displacement measurement of a structure with a rough surface. However, when the fringe scanning technique is introduced to speckle interferometry for improving the measurement resolution, generally two speckle patterns before and after the deformation of the measurement object and another speckle pattern obtained under different conditions from these two speckle patterns are required at least. So, three speckle patterns are generally required for precise fringe analysis as a minimum condition. In this paper, a method for introducing the fringe scanning method is proposed by controlling the phase of the specklegram as a fringe image using filtering techniques. Then, the temporal fringe analysis method that uses only two speckle patterns are proposed for speckle interferometry. As the result of experiments, it is shown that high precise fringe analysis can be realized by the fringe scanning methods using only two speckle patterns for the displacement measurement with a large deformation.     

Speckle reduction in optical coherence tomography by adaptive total variation method

An adaptive total variation method based on the combination of speckle statistics and total variation restoration is proposed and developed for reducing speckle noise in optical coherence tomography (OCT) images. The statistical distribution of the speckle noise in OCT image is investigated and measured. With the measured parameters such as the mean value and variance of the speckle noise, the OCT image is restored by the adaptive total variation restoration method. The adaptive total variation restoration algorithm was applied to the OCT images of a volunteer’s hand skin, which showed effective speckle noise reduction and image quality improvement. For image quality comparison, the commonly used median filtering method was also applied to the same images to reduce the speckle noise. The measured results demonstrate the superior performance of the adaptive total variation restoration method in terms of image signal-to-noise ratio, equivalent number of looks, contrast-to-noise ratio, and mean square error.     

Eine Inkohärente Methode Aktiver Optischer Übertragung

We report the results of a simulation, using diffuse laser light and an optical bench, of our recent holographic interpretation of Labeyrie's speckle interferometry. Our approach applies to a wide class of multiple objects (such as close binary, or higher order, stars) viewed through a turbulent medium (such as the atmosphere, under all ‘seeing’ conditions). Our results should encourage astronomers to attempt to image those multiple star systems whose individual components would be resolvable in large telescopes were there no atmosphere to contend with, but whose details are always, or usually, obscured by atmospheric seeing. We find that we can get clear images of collections of small, isolated objects after processing only 20 speckle interferograms (we must emphasize, though, that the signal to noise ratio is high in our experiments i.e. each interferogram contains several hundred speckles). We find that our reconstructions of large, continuous objects are recognizable, although appreciably distorted. We attribute this to the virtual unavoidable non-linearities introduced by our processing methods, which are entirely optical and photographic. We suggest that improved results would be obtained by a suitable combination of optical and digital processing procedures. We point out that our results support those who hope to improve the performance of inferior optical instruments by using processing methods inspired by statistical concepts.