Phase-shifting digital holography in image reconstruction

A phase-shifting digital holography scheme developed to investigate internal defects in artworks is described. Phase-shifting is utilized to obtain a clear reconstructed object wave from a rough surface texture. A reverse-transform algorithm is employed to reconstruct the object wave on its original position of unknown distance or the imaging position from the object wave information on the holographic plane. To get the clearest reconstruction the exact registration of the unknown distance is determined by applying the intensity sum as the auto-focusing function, The spatial resolution of the reconstruction image is also investigated for a variety of affecting factors. Laboratory results of reconstruction images under deformation are presented.

Possibility to break through limitation of measurement range in dual-wavelength digital holography

By using the beat frequency technique,the dual-wavelength digital holography(DWDH)can greatly increase the measurement range of the system.However,the beat frequency technique has a limitation in measurement range.The measurement range is not larger than a synthetic wavelength.Here,to break through this limitation,we propose a novel DWDH method based on the constrained underdetermined equations,which consists of three parts:(i)prove that the constrained underdetermined equation has a unique integer solution,(ii)design an algorithm to search for the unique integer solution,(iii)introduce a third wavelength into the DWDH system,and design a corresponding algorithm to enhance the anti-noise performance of DWDH.As far as we know,it is the first time that we have discovered that the problem of DWDH can belong in a problem of contained underdetermined equations,and it is also the first time that we have given the mathematical proof for breaking through the limitation of the measurement range.A series of results is shown to test the theory and the corresponding algorithms.More importantly,since the principle of proposed DWDH is based on basic mathematical principles,it can be further extended to various fields,such as dual-wavelength microwave imaging and dual-wavelength coherent diffraction imaging.

数字全息显微中相位像差校正技术综述

数字全息显微技术是数字全息技术与显微技术的结合,兼备两种技术的优点,为微纳领域的定量三维测量提供了一种无损、无标记、准确和近实时的测量手段。然而,由于元件缺陷和失调以及环境扰动等原因,会在数字全息显微测量结果中额外引入相位像差。为了获得准确的定量相位测量结果,必须对像差成因和主要成分进行分析,然后补偿和校正像差。这篇综述介绍了数字全息显微成像测量中主要的像差来源和影响,基于实现的方式对现有的像差校正方法进行了综述,并展望了未来像差校正领域的发展方向,为从事数字全息检测研究的研究者提供参考。

用于低相干干涉测量系统的多通道数字与模拟信号同步采集方法研究

在现代工程领域中,模拟信号和数字信号同步采集的重要性变得越来越显著。同步采集这两种类型的信号可以提高数据采集和处理的准确性、可靠性,并避免数据延迟、抖动等问题,尤其对于一些特定应用场景具有极高的必要性。为了适应低相干干涉测量系统中多类型多路信号的同步采集与处理需求,基于已有的数据采集仪,设计并制作了数字信号调理板,并通过实验验证了数字信号与模拟信号的同步采集情况。实验结果表明:所设计的系统不仅可以实现两种信号的高速同步采集,而且系统整体位移采集的精度很高:电动位移台在0~70 mm行程内,系统测量值与干涉仪测量值最大误差为2.52μm;压电位移台在0~320μm内,系统测量值与干涉仪测量值最大误差仅为0.54μm。

混凝土裂纹扩展过程的测量方法研究综述

为充分应用混凝土结构物的承载能力及保障其运营安全,需及时进行裂纹检测,并掌握裂纹扩展情况。针对混凝土裂纹扩展过程的试验测量,主要介绍了光弹性贴片法、云纹干涉法、电子散斑干涉法和数字图像相关方法4种测量方法,并从原理、特点以及在混凝土裂纹扩展过程测量中的应用等方面分析了4种方法的优缺点。结果表明:电子散斑干涉法和数字图像相关方法能更好地应用于混凝土裂纹的测量,本文成果可为混凝土裂纹扩展测量方法的选择提供一定的理论支撑。

融合小波与非局部均值滤波的DSPI相位图去噪

相位图去噪是数字散斑干涉测量的关键技术,但现有以正余弦均值滤波与窗口傅立叶变换滤波为代表的去噪方法在相位保真、自适应降噪、操作简便等方面不能完全满足要求。提出了一种新的自适应相位图去噪方法,首先计算原始相位图的噪声方差,然后对图像分别进行正弦与余弦变换后得到两幅图像,再对这两幅图像进行小波同态阈值去噪与非局部均值滤波,最后将处理后的两幅相位图反正切运算并再次估计噪声方差,根据图像噪声方差的收敛情况判断是否继续迭代处理,以实现相位图的自适应降噪。实验结果表明:针对同一张含噪相位图与传统正余弦均值滤波相比,本文方法噪声方差减少了0.38、L算子和减少了0.2、SSIM提高了0.16,同时,图像信息熵仅相差0.1。该方法能够有效抑制相位图中的相干噪声,充分保留相位边缘信息,同时能够有效避免因不适当的迭代滤波次数所导致的相位失真或噪声残留。

基于数字全息法测量光致聚合物的收缩

数字全息具有测量精度高、实时性强等优势,在诸多领域有极高的应用价值;光致聚合物作为光存储介质,是最有前途的全息记录材料之一,但记录过程中发生光聚合反应而引起的厚度收缩极大影响了记录效果,为测量其厚度的具体收缩量,提出一种基于数字全息的光致聚合物收缩率测量方法。以马赫曾德干涉光路为基础设计实验系统,记录光致聚合物反应前后的全息图,利用全息干涉计量的方法计算相位改变量,根据相位差与收缩的关系计算得到光致聚合物的收缩率。

Measurement of mass diffusion coefficients of O_2 in aviation fuel through digital holographic interferometry

The experimental apparatus to measure the mass diffusion coefficients of O2 in aviation fuel was constructed based on the digital holographic interferometry method. The theory of mass diffusion coefficient and interference image processing were introduced in detail. The accuracy of the experiment was verified by measuring the mass diffusion coefficient of 0.33 mol/L KCl in aqueous solution at 298.15 K. The mass diffusion coefficients of O_2 in RP3 and RP5 aviation fuels were measured at temperature from 278.15 K to 333.15 K, and the Arrhenius equation was employed to fit the experimental data. In terms of the Stokes-Einstein equation, the viscosities of these two aviation fuels were tested to estimate the correlation among mass diffusion coefficient, viscosity and temperature. A uniform polynomial calculation correlation was proposed to predict the mass diffusion coefficients of O_2 in both RP3 and RP5 aviation fuels, and its accuracy is considerably higher than that of the Stokes-Einstein equation.

光阑偏心对数字散斑干涉空间频谱的影响研究

光阑在空间域内对成像光束起到限制的作用,在光学系统中的应用十分广泛。在数字散斑干涉测量系统中,通常采用光阑对物光空间频率进行限制,便于针对待测目标完成后续的信号解调。理想情况下,光阑的中心位置应与光轴重合、且表面与光轴垂直,但在实际过程中,经常由于调整精度问题使得光阑中心偏离光轴,或者由于结构设计问题采用偏心光阑。本文以空间光束的傅里叶变换特性为基础,研究了光阑中心偏离光轴位置对物光和数字散斑干涉空间频谱的影响,并进行了实验验证,理论与实验结果一致。本文对数字散斑干涉系统关键参数设计,具有理论指导意义。

双站与重轨InSAR数据融合获取DEM的方法

多样性InSAR数据融合是弥补单基线InSAR生成DEM所存在不足的重要手段。鉴于以往的融合研究大多基于相同InSAR系统构型与工作模式的同源数据,文章提出一种双站与重轨InSAR异源数据融合获取DEM的方法和处理流程,重点研究了融合区域识别、重轨干涉大气校正等关键问题。为验证方法的有效性,使用一对天绘二号双站干涉数据结合多个异源重轨干涉数据进行融合,开展获取DEM实验,并采用GNSS实测数据和WorldDEM对DEM精度进行了验证。结果表明,融合后的DEM解缠错误及叠掩、阴影导致的无效点数明显减少,融合后的DEM相比单基线天绘二号干涉生成的DEM高程精度提高了11.6%。

Al-digital demodulation system of interferometric fiber optic sensors using an improved PGC algorithm based on fundamental frequency mixing

We present an all-digital demodulation system of interferometric fiber optic sensor based on an improved arctangent-differential-self-multiplying(arctan-DSM)algorithm.The total harmonic distortion(THD)and the light intensity disturbance(LID)are also suppressed,the same as those in the traditional arctan-DSM algorithm.Moreover,the lowest sampling frequency is also reduced by introducing anti-aliasing filter,so the occupation of the system memory is reduced.The simulations show that the improved algorithm can correctly demodulate cosine signal and chirp signal with lower sampling frequency.

Measurement of in-plane deformations of microsystems by digital holography and speckle interferometry(Invited Paper)

The reliability of microsystems is an important issue and for their quality inspection, it is necessary to know the displacements or deformations due to the applied mechanical, thermal, or electrostatic loads. We show how interferometrical techniques like digital holography and speckle interferometry can be used for the measurement of in plane deformations of microsystems with nanometric accuracy and we give a description of the measurement uncertainties.

Measurement of out-of-plane deformation of curved objects with digital speckle pattern interferometry

Digital speckle pattern interferometry （DSPI） is a high-precision deformation t technique for planar objects. However, for curved objects, the three-dimensional （3D） shape information is needed in order to obtain correct deformation measurement in DSPI. Thus, combined shape and deformation measurement techniques of DSPI have been proposed. However, the current techniques are either complex in setup or complicated in operation. Furthermore, the operations of some techniques are too slow for real-time measurement. In this work, we propose a DSPI technique for both 3D shape and out-of-plane deformation measurement. Compared with current techniques, the proposed technique is simple in both setup and operation and is capable of fast deformation measurement. Theoretical analysis and experiments are performed. For a cylinder surface with an arch height of 9 mm, the error of out-of-plane deformation measurement is less than 0.15 μm. The effectiveness of the proposed scheme is verified.

数字散斑干涉技术及应用

介绍了数字散斑干涉技术在位移、应变、振动和医学诊断等领域中的应用和国内外发展状况。提出了一种新的应用领域———数字散斑干涉技术在语音识别中的应用 ,并对该方法作了介绍 。

极具潜力的空间对地观测新技术——合成孔径雷达干涉

“合成孔径雷达干涉 (In SAR)”是近十年发展起来的空间对地观测遥感新技术。它具有从覆盖同一地区的星载 (或机载 )合成孔径雷达复数图像对提取干涉相位图 ,借助于雷达成像时的姿态数据重建地表三维模型 (即数字高程模型 )的巨大潜力。尤其是基于多幅雷达复数图像处理的差分干涉技术 (D- In SAR)可以用于监测地表形变 ,精度可达厘米级甚至更高 ,其监测空间分辨率是前所未有的。介绍了 In SAR和 D- In SAR的基本原理 ,对影响干涉结果的一些重要因素做了分析 ,重点回顾和展望了差分干涉技术在与地表形变有关的地震监测和震后形变测量、地面下沉和山体滑坡、火山运动监测等方面应用的现状和前景。

用InSAR技术进行形变监测的研究

卫星合成孔径雷达干涉技术((InSAR)通过对地面同一地区两次或多次平行观测成像得到的复图象对进行处理可获得数字地面模型,用以监测地表面变化。本文简单叙述了(InSAR)基本原理、处理流程及方法,并通过天津SAR数据的处理,详细介绍了SAR数据处理整个过程,之后给出了基于ERS-2天津地区原始数据的实验结果形成的干涉图及数字高程图。

散斑干涉相位条纹图的频域滤波处理

为了解决在数字散斑干涉技术测量时,散斑干涉相位条纹图像中大量噪声对相位解包裹结果和精度产生严重影响的问题,介绍了一种条纹正余弦分解和频域低通滤波结合的方法,实现了散斑干涉相位条纹图的高精度滤波。该方法的基本思路是在对相位图像进行滤波处理前,先将相位图通过正余弦函数进行映射转换成两幅图,分别经过频域滤波,然后再合成为相位图。这种分解频域滤波方法可以在滤波的同时,有效保留相位跳变信息。实验结果表明：与传统的图像降噪方法相比,该方法能够在保留图像＂尖峰＂信息的基础上,较好地滤除图像中的散斑噪声,方法简单有效,有效解决了传统滤波方法应用在相位条纹图中,相图灰度信息丢失10%~40%的问题。

合成孔径雷达干涉测量原理与应用

合成孔径雷达 (SAR)是一种微波相干成像方法 ,应用不同波段的雷达信号可以对地球表面不同的散射特性成像。合成孔径雷达干涉 (InSAR)是将两个不同轨道位置或不同时间获得的复数SAR数据进行相位差分处理 ,从这些差分干涉数据中可以提取特别有用的信息 ,用于绘制地形图 ,测量诸如地震、火山、冰川运动等造成的地形变 ,研究植被覆盖特性、洋流等。介绍了InSAR的基本原理与应用 ,并对影响干涉结果的一些重要因素进行了分析。

基于两步正交相移干涉的振幅图像光学加密技术

提出一种基于两步正交相移干涉的光学图像加密技术.这种相移干涉数字全息只要记录两幅干涉图,不需要记录物光波和参考光波的强度信息,就可以再现没有零级像和共轭像的再现像.物光波对应的光路经过两次菲涅尔变换,并结合双随机相位编码.参考光分别引入0和π/2相位,用数字化记录介质记录两幅数字全息图作为加密图像.解密时只要获得正确的密钥,经过简单的计算就可以重建清晰的原始图像.模拟实验验证了它的可行性和有效性,分析了抗裁剪和噪音的鲁棒性.

基于数字全息干涉术的液相扩散过程可视化（英文）

提出了利用数字全息干涉术可视化观测液相扩散过程.实验中,采用马赫-曾德干涉仪光路记录乙醇与水之间两相扩散过程的多幅数字全息图;再通过数值再现不同扩散状态的波前相位分布,获得液体中的摩尔浓度分布;最后,根据菲克定律获得两相流扩散系数.结果表明:利用数字全息干涉术可实现对液相扩散传质过程的快速、实时及高精度测量;该方法还具有可实现远程监控、拥有大量微观数据的优点;此外,采用文中全息干涉光路结合波分与角分复用技术可实现多相流扩散系数的测量,为获得溶液中非线性变化特征参量提供了有效技术手段.