In vivo 783-channel diffuse reflectance imaging system and its application

A fiber-based reflectance imaging system was constructed to produce in vivo absorption spectroscopic images of biological tissues with diffuse light in the cw domain. The principal part of this system is the 783-channel fiber probe, composed of 253 illumination fibers and 530 detection fibers distributed in a 20x20 mm square region. During illumination with the 253 illumination fibers, diffuse reflected lights are collected by the 530 detection fibers and recorded simultaneously as an image with an electron multiplying CCD camera for fast data acquisition. After signal acquisition, a diffuse reflectance image was reconstructed by applying the spectral normalization method we devised. To test the applicability of the spectral normalization, we conducted two phantom experiments with chicken breast tissue and white Delrin resin by using animal blood as an optical inhomogeneity. In the Delrin phantom experiment, we present images produced by two methods, spectral normalization and reference signal normalization, along with a comparison of the two. To show the feasibility of our system for biomedical applications, we took images of a human vein in vivo with the spectral normalization method.     

光纤连接器用插针材料

光纤连接器是使用量最大的光无源器件，实现光纤的插针是光纤连接器的重要部件，极高的尺寸精度要求使其成为光纤连接器生产的技术关键。介绍了各种光纤连接器插针材料；氧化锆（PSZ）陶瓷是目前使用量最大的光纤连接器插针材料。     

基于显微光学成像的微细纤维测量识别系统光源优化研究

显微光学成像的纤维识别系统的照明光源,对成像质量有很大影响。由于单个LED光源发光功率有限,且在照射面的光分布不均,导致系统采集到的微纳米级纤维(单丝平均直径15～40μm)图像模糊,影响测量与识别结果的准确性。根据LED的光学特性,对系统的照明光源进行优化设计,设计了3种不同的LED平面光源阵列,并根据LED阵列光源在照射面上的照度表达式,仿真模拟给出LED阵列的照度分布,并以实验进行验证,对系统实际检测的图像进行图像识别处理和图像参数峰值信噪比评价,给出优化结果。研究结果表明,优化后的LED平面光源阵列有效地解决了照度不均导致的微细纤维图像模糊识别不清的问题,优化后得到的纤维样品图像边缘清晰,有效提高了系统检测纤维样品的图像质量,为微细纤维测量识别与研究提供了新的途径。     

Formation of speckle images formed for diffusers illuminated by modulated apertures (circular obstruction)

An amplitude modulation of circular aperture is used for the illumination of a numerical object having a randomly distributed function. In this study, a central obstruction for the aperture is assumed. The modulated speckle image is obtained using the MATLAB program and compared with that obtained in the case of an uniform circular aperture for the illumination. We have considered coherent illumination obtained from a laser beam in order to facilitate the computation of the Fourier transform of the defined computed speckle intensity corresponding to this novel aperture. Finally, the autocorrelation function of the randomly distributed object is calculated in all cases.     

A practical approach for estimating illumination distribution from shadows using a single image

This article presents a practical method that estimates illumination distribution from shadows using only a single image. The shadows are assumed to be cast on a textured, Lambertian surface by an object of known shape. Previous methods for illumination estimation from shadows usually require that the reflectance property of the surface on which shadows are cast be constant or uniform, or need an additional image to cancel out the effects of varying albedo of the textured surface on illumination estimation. But, our method deals with an estimation problem for which surface albedo information is not available. In this case, the estimation problem corresponds to an underdetermined one. We show that the combination of regularization by correlation and some user‐specified information can be a practical method for solving the underdetermined problem. In addition, as an optimization tool for solving the problem, we develop a constrained Non‐Negative Quadratic Programming (NNQP) technique into which not only regularization but also multiple linear constraints induced by user‐specified information are easily incorporated. We test and validate our method on both synthetic and real images and present some experimental results. © 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 15, 143–154, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.20047     

Reconstruction and quantitative analysis of metallic surfaces with pits based on improved stereo image matching method

A stereo image matching method is developed for the solution of the problem of reconstruction of surfaces with corrosion defects. Special attention is given to the problem of improvement of mathematical models of an objective function and methods for its optimization in the presence of shaded regions in the images of a metal surface, which are observed in the investigation of pit-like defects. The proposed method is used for the quantitative analysis of the depth and shape of local pitting corrosion.     

Static non-linear three-dimensional analysis of a riser bundle by a substructuring and incremental finite element algorithm

The problem of static, non-linear, large three-dimensional deformation of riser bundles used in offshore oil and gas production is studied within the limits of small strain theory. The mathematical model consists of the models of component-risers and connectors which hold risers together. Each riser is modelled as a thin walled, slender, extensible or inextensible tubular beam-column. It is subject to non-linear three-dimensional deformation dependent hydrodynamic loads, torsion and distributed moments, varying axial tension, and internal and external fluid forces. The problem is solved numerically by developing an algorithm which features substructuring, condensation and non-linear incremental finite elements. Substructuring is used to decompose the riser bundle problem into those of individual component-risers and equilibria of connectors. Condensation is used along with the connector equilibrium equations to produce connector forces and moments. Strong non-linearities present in the model are handled by an incremental finite element approach. Accuracy of the computer code is verified by solving simple three-dimensional cases. Two three-dimensional applications are solved for a bundle with seven component-risers and up to a total of 1267 degrees of freedom. Finally, a comparison is made with numerical results of a two-dimensional analysis code. The influence of problem size on total CPU time is discussed.     

Image Processing of Manganese Nodules Based on Background Gray Value Calculation

To troubleshoot two problems arising from the segmentation of manganese nodule images-uneven illumination and morphological defects caused by white sand coverage, we propose, with reference to features of manganese nodules, a method called “background gray value calculation”. As the result of the image procession with the aid this method, the two problems above are solved eventually, together with acquisition of a segmentable image of manganese nodules. As a result, its comparison with other segmentation methods justifies its feasibility and stability. Judging from simulation results, it is indicated that this method is applicable to repair the target shape in the image, and segment the manganese nodule image in a short time. Also, it could be used to synchronously process a large number of manganese nodules on different conditions in an image, laying a good foundation for automatic underwater manganese nodule survey. Even if the target in the image is slightly distorted, the statistical data of manganese nodules are still accurate. Moreover, other methods cannot be fully applied to the segmentation of manganese nodule images; in another word, the effectiveness and stability of this method are proved.     

Directional textures auto-inspection using discrete cosine transform

This paper describes a global image restoration scheme using a discrete cosine transform (DCT) that can be used to detect defects in directional textured surfaces automatically. The input spatial domain image is first transformed into the DCT domain so that the dominant directions of the texture in the input image will be compacted into the orthogonal straight lines or impulses through the direct current (DC) component of the spectrum. The linear primitives associated with the high-energies in the DCT domain are eliminated by reducing them to zero before transforming back to the spatial domain. Finally, the defects, if any, are extracted by the thresholding method. Experiments on a variety of product surfaces with directional textures such as straight, slanted, orthogonal, slanted orthogonal, and oblique linear primitives were conducted in this paper. The proposed scheme would blur directional textures and preserved only local defects if they were initially embedded in the image. Furthermore, some preliminary experiments were also conducted to demonstrate the proposed scheme was insensitive to horizontal and vertical shifting, changes in illumination, and image rotation.     

精密微小型零件自动装配系统显微机器视觉的照明自动优化

为了在微小型零件装配过程中始终获得质量最佳的零件图像,对显微视觉照明光强的自动优化问题进行了研究。为实现对零件的轮廓边缘与表面细节的照明,基于同轴光源与环形光源开发了照明自动控制系统。对比分析了四种图像质量评价函数的照明优化性能,提出了基于Roberts梯度和函数的图像质量评测方法,并应用于研制的装配系统。装配实验结果表明,光强优化过程快速准确,光强优化后目标边缘的对比度显著增强,消除了零件误识别现象,满足微小型零件高精度装配自动化的要求。     

Automatic defect inspection of patterned thin film transistor-liquid crystal display (TFT-LCD) panels using one-dimensional Fourier reconstruction and wavelet decomposition

Large-sized flat-panel displays have become increasingly important for use in computer monitors and televisions. This paper has considered the problem of automatic visual inspection of micro-defects including pinholes, scratches and particles in patterned thin film transistor-liquid crystal display (TFT-LCD) panel surfaces. For large-sized TFT-LCD panel inspection, high-resolution line scan is demanded. We propose a global one-dimensional (1-D) Fourier-based image reconstruction scheme that directly works on the 1-D line images instead of the traditional two-dimensional area images. The proposed method fully uses the inherent geometric structure of a TFT-LCD panel. It first eliminates the frequency components that represent the periodic pattern of a TFT-LCD line image in the 1-D Fourier spectrum and then back-transforms the 1-D Fourier-domain image to the 1-D spatial domain image using the inverse Fourier transform. The Fourier reconstruction process can effectively remove the patterned background and distinctly preserve local anomalies in the resulting 1-D image. Wavelet decomposition is further applied to remove uneven illumination in the filtered image so that defects can be easily segmented with simple statistical control limits. Experimental results on a number of micro-defects embedded in TFT-LCD panels show that the proposed method can reliably detect various ill-defined defects without designing and measuring the quantitative features of individual defect types.     

玻璃表面缺陷检测系统研究

目的针对玻璃表面存在的划痕、漏点、结石和水印等4种主要缺陷,研究一种基于背光照射的玻璃表面缺陷检测方法,提出一种改进K均值聚类算法用于水印缺陷的检测。方法首先,通过设计的图像采集系统对玻璃图像进行采集,并对采集图像背景估计;然后根据水印缺陷与其他3种缺陷的灰度差异,将含缺陷的玻璃分成2类,完成缺陷粗分类;接着利用边缘检测算法对含划痕、漏点和结石缺陷的玻璃图像进行处理,利用结合了Otsu阈值分割方法和补偿系数f的改进K均值聚类算法对含有水印缺陷的玻璃图像进行处理,最终实现对玻璃表面4种缺陷的识别与标记。结果实验表明,该系统操作方便,算法复杂度低,缺陷识别准确度高,检测速度快。结论通过上述玻璃表面缺陷检测系统,可准确高效地检测出玻璃表面存在的4种主要缺陷。改进的K均值聚类可以准确实现对水印缺陷的检测,且该方法可以克服聚类迭代次数高,聚类结果容易陷入局部最小等缺点。极大地提高了缺陷检测的效率,可用于玻璃生产过程中的实时检测。     

红外热成像技术在电连接器插拔磨损检测中的应用研究

接触件是电连接器的核心元件,因插拔产生的磨损会导致其电接触性能退化甚至失效。针对上述问题,提出了一种电连接器插拔磨损检测方法。基于设计的检测装置开展电连接器插拔试验,并在试验过程中对电连接器接触件进行定时红外热成像检测;同时,分析插拔过程中电连接器接触件间磨屑的分布特征及变化规律,并通过表面形貌分析和能谱分析来验证红外热成像分析结果。研究发现,电连接器插孔簧片的主要磨损区域为端部,其根部有少量磨屑且聚集区域相对分散;随着插拔次数的增加,电连接器接触件间的磨屑逐渐增多,磨损区域面积逐渐增大,且磨屑聚集的位置也随着插拔运动发生变化,随机地分布在接触件间;因存在加工误差,电连接器的插孔簧片非对称分布,使得不同插孔簧片的磨损程度存在差异。结果表明,所提出的检测方法可有效观察电连接器接触件插拔磨损的变化过程,可作为电连接器磨损程度在线监测及剩余寿命预测的有效手段。研究结果可为电连接器性能退化机理和失效分析提供依据。     

Characterization of plastic shrinkage cracking in fiber reinforced concrete using image analysis and a modified Weibull function

Numerous strategies have been advocated to reduce the potential for plastic shrinkage cracking in concrete through mixture proportioning, curing methods, or the use of fiber reinforcement. The effectiveness of each approach must be adequately quantified to determine whether the additional initial cost of each strategy is justified. The majority of current research to characterize plastic shrinkage cracking in concrete relies on manual crack observation and measurement that is typically only performed at select locations. These manual measurements of crack width may provide only limited information and may be subject to operator bias. This paper describes a systematic methodology that uses a semi-automated image analysis approach to accurately quantify the salient features of the plastic shrinkage crack patterns. A restrained slab specimen with a stress riser was used to amplify the potential for plastic shrinkage cracking. The specimens described in this paper were exposed to an accelerated drying environment for the first 6 hours after casting. At an age of 24 hours, the crack was assessed using a series of thirteen gray level images that were acquired along the crack path. Crack contours were extracted from these images using gray level intensity thresholding to create binary images. Subtracting the binary image from a uniformly spaced grid enabled the crack width to be determined at numerous locations. This image analysis technique permits the crack widths to be assessed rapidly at numerous locations without operator bias. The measured crack widths were statistically analyzed using a modified Weibull distribution function. This enabled the crack width distribution to be fully described using only two or three parameters. It is anticipated that this approach can be used to better quantify the effects of short randomly distributed fiber reinforcement on plastic shrinkage crack formation.     

Location of Optical Fibers for the Calibration of Incoherent Optical Fiber Bundles for Image Transmission

Image transmission by incoherent optical fiber bundles (IOFBs) requires prior calibration to obtain the spatial in–out fiber correspondence to reconstruct the image captured by the pseudocamera. This information is recorded in a lookup table (LUT), which is later used for reordering the fiber positions and reconstructing the original image. This paper shows how to apply a fiber detection process to minimize the calibration time and improve the quality of the recovered image. Two different fiber detection methods were developed. The former uses the circular Hough transform algorithm based on the image gradient. The second algorithm combines a number of morphological transformations with distance transform. The results demonstrate that this technique provides a remarkable reduction in the processing time while improving fiber detection accuracy.      

基于图像配准的STN-LCD外观缺陷检测

提出了一种基于图像配准的超扭曲向列液晶显示器件(STN-LCD)的外观缺陷自动检测方法.该方法首先对标准模板图像做不均匀光照消除、二值化以及区域信息提取;然后通过控制点检测和仿射变换实现待检测图像和模板图像之间的配准;并利用各图形区域的灰度平均值和标准方差等统计信息,检测缺段、针孔等各类缺陷.为提高图像配准精度,进一步提出了有效控制点筛选方案以及混合插值方法.实验结果表明,该方法设计思路合理,缺陷检测正确率达到98.3%,可代替人眼实现对STN-LCD多种外观缺陷的快速、自动检测,满足实际应用需求.     

光纤连接器端面超声机械研磨

为了提高光纤连接器端面的加工效率和加工质量，改善连接器光传输性能，探讨了在机械研磨的界面上引入超声能的复合研磨方式，设计了相应的超声机械研磨装置．实验结果显示，超声机械研磨效率是机械研磨的4～8倍，光纤表面粗糙度达到2～5nm，插入损耗小于0．1dB、回波损耗小于-60dB．研究表明，超声机械研磨技术可以提高光纤连接器的研磨效率和质量，使传输性能获得显著改善．     

Effect of polishing conditions on terminating optical connectors with spherical convex polished ends

Increased demand for fiber-optic technology has created significant growth in the sales of interconnection devices such as fiber-optic connectors, cable assemblies, and adapters. To ensure good connector performance during actual use, several process parameters related to geometric and optical characteristics of the connector must be thoroughly understood during the manufacturing stage. The experimental design has been used here to see the influence of applied pressure and time on the fiber end geometry as well as optical performance. The mathematical model is also applied to explain the phenomena of the present fiber undercut-reflectance relation. By a proper choice of polishing film grit size and processing conditions, it is possible to obtain fiber connectors with less fiber undercut and better return loss. Influences of film grit size and rubber-pad thickness on the reflectance and the fiber undercut are also presented.     

High-precision measurement of a fiber connector end face by use of a Mirau interferometer

What we believe to be a new instrument for measuring the end-face geometrical parameters of fiber connectors is described. In this apparatus, a Mirau-type interferometric objective is employed to measure a small area of the connector end face and generate an interferogram corresponding to the surface profile. Various new technologies are used to ensure excellent performance and high measurement repeatability. A multipoint method is proposed to adjust the inclination of the physical contact sample stage. The physical contact angle of the sample stage is adjusted directly on the instrument by use of a special tool whose angle is calibrated with the reversal method. Measurement results of important parameters of the fiber connector end face are compared with those inspected by a commercial profiler or with a standard sample. Optical insertion losses of connectors inspected by the developed system are also evaluated.