改进的强度相干成像室内实验方法

设计了一种新的强度相干成像室内实验方法,以简化现有强度相干实验过程,获取接近实际观测的测量数据。首先,分析了强度相干成像原理及影响成像质量的因素;介绍了现有强度相干成像实验方法并分析其存在的不足。然后,利用赝热光源和CCD设计了一种新的强度相干成像方法;介绍了利用此种方法模拟强度相干成像的原理及特点。最后,进行了室内强度相干成像实验,验证了提出方法的可行性。实验结果表明:利用提出的实验方法能够较好地测量目标的空间功率谱,测量噪声主要分布在高频部分;当测量信噪比大于20时,利用相位恢复方法可恢复获得较好的目标光强分布图像。实验显示,提出的成像方法能够较好地模拟强度相干成像,实验中能够较为方便地调节光强随机涨落并观测基线参数,实现对小角直径目标的有效成像。     

光学系统清晰成像的逆源研究

在建立部份相干系统成像的数学模型之后,本文讨论相干度对成像的影响,提出了改善成像清晰度的逆源方法:按所需相干度求出适当光源,不论像面是否处于准确位置,其成像清晰度较通常优良成像系统有明显地提高。并用实验证实了这种方法。     

计算成像技术在光学检测领域的研究进展

成像系统在利用传感器记录图像信息时,只记录了强度信息而丢失了重要的相位信息。 传统的干涉相位恢复技术由于 需要满足严格的干涉条件,在使用过程中受到一定限制。 随着计算成像技术的蓬勃发展,以强度传输方程和相干衍射成像以及 在此基础上发展起来的相干调制成像、叠层扫描相干衍射成像为代表的非干涉相位恢复技术受到广泛关注,并被运用于光学检 测领域。 这类技术无需参考光,系统结构简单,可通过衍射强度图直接获得相位信息,在检测领域有巨大的应用潜力。 基于此, 介绍了几种典型的计算成像技术的研究现状与最新进展,同时讨论分析了各类方法的主要技术特点。     

二维频域光学相干层析系统研究

针对时域光学相干层析成像系统的成像速度较慢的问题,采用VC++与Matlab混合编程技术开发了二维频域光学相干层析成像系统,实现了对被测样品进行内部快速成像;搭建二维频域光学相干层析成像系统代替一维频域光学相干层析成像系统;利用计算机驱动面阵CCD相机对干涉信号进行采集得到干涉信号;采用计算机驱动NI卡对压电陶瓷(PZT)移相器进行相移控制以达到频域光学相干层析成像系统对移相的需求,利用计算机驱动线性电动移动平台实现检测样品进行横向扫描以达到对样品进行三维成像。研究结果表明,该系统集成度高,开发的软件功能齐全、界面友好、便于维护和升级;该二维系统相比一维光学相干层析成像系统而言减少了一维的扫描采集次数,大大提高了成像速度。     

谱域OCT系统设计与实验研究

光学相干层析成像（Optical Coherence Tomography,OCT）是一种非侵入、非接触的新型光学成像技术,利用生物组织的后向散射光与参考光之间的弱相干实现结构成像,具有高灵敏度、高分辨率、成像速度快等特点。本文设计了一套基于LabVIEW软件平台下的谱域OCT成像系统,并对系统进行了测试与实验研究,验证了系统的可靠性与准确性。     

利用全息成像系统实现非相干成像

相干激光束应用在全息成像系统的制作中。这项研究目的是,也把这类系统用在空间非相干照明物体,和多色光(如日光)照明物体的成像方面。     

短相干照明与偏振相结合的水下远距离成像

随着透明海洋战略的提出,低成本的凝视成像装备在水下光学成像中独具优势。然而,后向散射和成像目标难以分离,远距离凝视成像极为困难。更为严重的是,在采集到有效目标图像之前,过强的后向散射噪声已经使图像提前饱和,无法进行后续处理。本文提出了短相干照明与偏振成像相结合的水下远距离成像方法,利用短相干光源照明简化后向散射与成像目标的分离过程,同时,采用偏振技术有效抑制后向散射,防止图像提前饱和,保障目标图像的有效采集。为此,搭建了大型水下光学成像实验平台,并对22 m的远距离水下目标进行了成像试验研究。试验结果表明,该复合成像方法获得的图像信噪比由0.50 dB提高到13.57 dB,设备的抗提前饱和能力提高了1.42倍,优于传统的偏振成像,可以为大范围水下光学监控提供技术支撑。     

临床X射线相衬成像研究进展

X射线相衬成像在提高人体软组织成像的衬度分辨率及空间分辨率研究中具有潜在优势,是一项有着广阔发展前景的技术。它利用空间相干X射线投过物体后携带的相位信息进行成像,在临床上适用于软组织物体,可以减少吸收剂量,进而减轻病人的辐射损伤。本文详述了当今几种典型的X射线相衬成像方法,包括X射线干涉相衬,衍射增强相衬以及类同轴相衬的成像原理以及发展历程。通过对比表明了几种成像方法的优缺点。最后对临床X射线相衬成像有待解决的问题作了分析。     

光学相干层析系统的建立与研究

介绍了光学相干层析 ( OCT)成像技术的原理及应用 ,阐述了自行研究建立的OCT系统 ,给出了利用该系统得到的实际生物样品光学相干层析图像 ,对系统性能和结果作了分析 ,提出一定的改进方案     

光学相干成像技术在激光加工过程实时监测与控制中的应用研究进展

激光加工技术,主要包括激光焊接技术、激光增材制造技术和激光减材制造技术,具有高加工质量、效率、无工具磨损等优点,在航空航天、生物医疗、通讯电子等领域应用广泛。随着产品精度与性能要求的逐渐提升,对激光加工的精度、效率及可控性提出了更高要求。因此,激光加工过程实时监测及调控成为当前的研究重点。相比于传统的光声热电传感监测,光学相干成像技术可以与激光束同轴耦合,从而直接获取激光加工结构的尺寸和形貌特征,具有高成像速度、高测量分辨率以及长测量范围等优点,被广泛应用于激光加工过程实时监测中。系统介绍了光学相干成像系统的基本组成、成像原理以及系统指标,在此基础上综述了光学相干成像技术在激光焊接、激光增材制造和激光减材制造实时监测与控制中的应用。最后,归纳了目前光学相干成像技术在激光加工过程监测中存在的不足和发展趋势,为激光加工过程实时监测与控制的研究工作提供了坚实基础和发展方向。     

Retrospective shading correction based on entropy minimization

Shading is a prominent phenomenon in microscopy, manifesting itself via spurious intensity variations not present in the original scene. The elimination of shading effects is frequently necessary for subsequent image processing tasks, especially if quantitative analysis is the final goal. While most of the shading effects may be minimized by setting up the image acquisition conditions carefully and capturing additional calibration images, object-dependent shading calls for retrospective correction. In this paper a novel method for retrospective shading correction is proposed. Firstly, the image formation process and the corresponding shading effects are described by a linear image formation model, which consists of an additive and a multiplicative parametric component. Secondly, shading correction is performed by the inverse of the image formation model, whose shading components are estimated retrospectively by minimizing the entropy of the acquired images. A number of tests, performed on artificial and real microscopical images, show that this approach is efficient for a variety of differently structured images and as such may have applications in and beyond the field of microscopical imaging.     

提高FMS加工零件图像识别精度的一种有效方法

根据轴套类FMS加工零件外形的特点,应用图像识别原理、几何光学成像原理,提出在FMS系统上实现“物体在同一平面上任意两尺寸的比值等于所成像中这两尺寸的比值“图像相关识别方法,阐述为实现该方法的和体边缘探测与特征值提取的“变模板法”等动态实时处理方法与技术,此识别方法提高了FMS系统运行中零件图像识别精度、稳定性和可靠性。     

Vision-based formation control of aerial robots in the presence of sensor failure

This article presents vision-based formation flight control for aerial robots with a special focus on failure conditions in visual communication. Then, by proposing and combining two strategies, a new solution is presented for formation control. In vision-based formation flight, the state variables of the leader are estimated using image processing and unscented Kalman filter. The follower adjusts its position with respect to the leader based on the results of the estimation. In the case of visual communication failure an error will occur in the estimation of variables, which would increase with the decreased image quality. In the first proposed strategy, during the failure emergence, the position of the follower aerial robot is obtained by combining the unscented Kalman filter's estimated velocity vector and the velocity vector before failure. The weighting coefficient of each velocity vector is obtained by fuzzy logic and based on image quality. In the second strategy, to reduce the possibility of collision between the members, the geometry of the formation pattern is expanded as a function of image quality and the distance between the members. The expansion coefficient is also extracted by a fuzzy inference method, and the desired distance between the members is increased as a function of expansion coefficient. These two strategies are combined to be used during failure periods. Finally, simulation studies are presented which are conducted based on the system nonlinear equations, a model with 6 degrees of freedom for each member, and the proposed visual noise model. Obtained results reveal the proper capability of the proposed hybrid strategy in terms of controlling the formation flight during failure conditions.

     

Quantitative phase-amplitude microscopy I: optical microscopy

In this paper, the application of a new optical microscopy method (quantitative phase‐amplitude microscopy) to biological imaging is explored, and the issue of resolution and image quality is examined. The paper begins by presenting a theoretical analysis of the method using the optical transfer function formalism of Streibl (1985 ). The effect of coherence on the formation of the phase image is explored, and it is shown that the resolution of the method is not compromised over that of a conventional bright‐field image. It is shown that the signal‐to‐noise ratio of the phase recovery, however, does depend on the degree of coherence in the illumination. Streibl (1985) notes that partially coherent image formation is a non‐linear process because of the intermingling of amplitude and phase information. The work presented here shows that the quantitative phase‐amplitude microscopy method acts to linearize the image formation process, and that the phase and amplitude information is properly described using a transfer function analysis. The theoretical conclusions are tested experimentally using an optical microscope and the theoretical deductions are confirmed. Samples for microscopy influence both the phase and amplitude of the light wave and it is demonstrated that the new phase recovery method can separate the amplitude and phase information, something not possible using traditional phase microscopy. In the case of a coherent wave, knowledge of the phase and amplitude constitutes complete information that can be used to emulate other forms of microscopy. This capacity is demonstrated by recovering the phase of a sample and using the data to emulate a differential interference contrast image.     

A focusing algorithm for high magnification cell imaging

An algorithm to produce a uniformly focused image in digital acquisition of high magnification light microscopy images is presented. In very high magnification microscopic imaging the specimen surface cannot be considered ideally flat so that capturing a single image frame is usually not sufficient to capture an image that is focused everywhere. An image formation model for light microscopic images is presented, and based on this model an algorithm to construct a uniformly focused image is presented. The algorithm requires that multiple frames of the image at different focal planes be processed to combine their information to obtain an estimated of the desired image which is more completely focused than any of the individual frames. Experimental results show that the proposed algorithm is very effective in approximating the desired image in high magnification microscopic imaging and highly robust comparing to the gradient method.     

基于跨尺度字典学习的图像盲解卷积算法

在模糊核未知情况下利用模糊图像对清晰图像进行复原称为图像盲解卷积问题,这是一个欠定逆问题,现有的大部分算法通过引入模糊核和清晰图像的先验知识来约束问题的解空间。本文提出了一种基于跨尺度字典学习的图像盲解卷积算法,采用降采样图像训练稀疏表示的字典,并将图像纹理区域在该字典下的稀疏表示作为正则化约束引入盲解卷积目标函数中。图像降采样过程减弱了图像的模糊程度,且图像中存在冗余的跨尺度相似块,利用更清晰的图像块训练字典能够更好地对清晰图像进行稀疏表示,减小稀疏表示误差;同时,由于在纹理区域清晰图像的稀疏表示误差小于模糊图像的稀疏表示误差,在该字典下对图像中的纹理块进行稀疏表示,使重建图像偏向清晰图像。本文的算法在Kohler数据集上复原结果的平均峰值信噪比为29.54 dB。在大量模糊图像上的实验验证了本文的算法能够有效解决大尺寸模糊核的复原,并具有良好的鲁棒性。     

Spectroscopic study of the image formation in near-field microscopy, near an evanescent-homogeneous switching

Near-field optical microscopes provide highly resolved images of various samples. However, images are difficult to interpret owing to their sensitivity to illumination conditions. Moreover, by contrast with classical microscopy, the near-field signal combines the contributions of evanescent and propagative modes. In this study, we present results of a spectroscopic study in near-field. Our purpose is to explain how a switching of one diffracted mode from homogeneous to evanescent can modify image formation. The main point is to establish a relation between the evanescence of one diffracted mode and the fringes that are often observed in near-field experimental images. Moreover, on a metallic sample, the possible occurrence of plasmon resonance contributes to image distortion in a mainly different way. We use a Fourier series Rayleigh 3D method to explain image formation.     

Spectroscopic study of the image formation in near-field microscopy, near an evanescent–homogeneous switching

Near-field optical microscopes provide highly resolved images of various samples. However, images are difficult to interpret owing to their sensitivity to illumination conditions. Moreover, by contrast with classical microscopy, the near-field signal combines the contributions of evanescent and propagative modes. In this study, we present results of a spectroscopic study in near-field. Our purpose is to explain how a switching of one diffracted mode from homogeneous to evanescent can modify image formation. The main point is to establish a relation between the evanescence of one diffracted mode and the fringes that are often observed in near-field experimental images. Moreover, on a metallic sample, the possible occurrence of plasmon resonance contributes to image distortion in a mainly different way. We use a Fourier series Rayleigh 3D method to explain image formation.     

基于形态学和小波的视觉图像模糊检测弧焊质量控制研究

焊接过程自动控制一直是焊接界研究的前沿课题,而焊接视觉图像检测是实现焊接过程自动控制的重要步骤。针对弧焊过程中焊接图像噪声大、稳定性差的特点,提出了一种基于小波降噪和形态学模糊检测的算法。通过将该图像检测算法应用于焊接动态过程熔池图像的处理,并结合模糊PID闭环控制理论,一套完整的弧焊过程熔透控制系统在得以研究实现。通过对Q235钢板的TIG焊工艺实验表明,该控制系统可以有效地克服焊接过程中的外界干扰,从而保证焊缝成形质量的稳定。     

Colour display of video information in scanning electron microscopy: Principles and applications to physics,geology, soil science,biology, and medicine

From a colourimetric point of view, colour has two independent aspects: brightness and chromaticity. In black and white images, all elements are of the same chromaticity and can be distinguished only by brightness contrast. In the colour image, elements of the same brightness can be discriminated by chromaticity (colour) contrast. Generally, colour image elements can be discriminated both by brightness and by chromaticity. As the human eye can distinguish a number of hues two orders of magnitude larger than the number of grey levels, it is safe to say that the colour image is much more informative than the black and white image. There are some peculiarities of the colour image and methods of its formation in SEM. Two principles of image formation are used. The first consists of the formation of a real colour image in the cathodoluminescence mode. In this case the colour of an image element is determined by the spectrum of the luminescence emission excited in the corresponding point of an object by the electron beam. The second principle is that of colour coding (quasicolour, pseudocolour), when a video signal in colour (either digital or analog) corresponds to a video signal (amplitude, frequency, phase, etc.) produced by any mode in the scanning electron microscope. We present a review of the methods of colour display of video information in scanning electron microscopy and their applications to physics, geology, soil science, biology, and medicine.