光强传输方程与图像插值融合的相位恢复

光强传输方程作为典型的相位恢复技术,在已知待测面光强分布与光强轴向微分时,可以通过求解该方程直接得到待测面的相位分布。强度微分可以通过采集沿传播方向的不同散焦面的光强信息以计算强度差分来估计,由此,散焦面的适当选择变得尤为重要。将光强传输方程与图像插值法相结合,在几何光学模型下描述采集的散焦面光强分布与聚焦面光强分布之间的关系,再利用图像插值法计算出模糊参数不同的散焦面的光强分布,由新得到的散焦图和采集的聚焦图代入光强传输方程以计算出相位。该方法只需要采集三幅强度图像,即可计算获得其他位置的强度图像,避免了采集设备的多次移动,也为某些特殊情况下无法获取适合位置的强度图像提供了一种解决途径。实验中搭建了一个实际的光强图像获取系统,所得结果验证了所提算法的有效性。     

A Fiber Splicing-Plane-Inspection Technique Using Lens–Fiber Interference for the Cascaded Fiber Fabrication

In this paper, a novel inspection technique for the cascaded fiber fabrication is proposed to improve the coupling performance of such fibers. Instead of using a direct-monitoring method, an indirect technique with the help of the ray tracing and the lens-fiber interference is used. By calculating the optical-path length of the light rays passing through the fiber, the interference fringes and light intensity can be counted. Then, the splicing plane of the cascaded fiber can be determined by observing the difference between the two fiber sections. Simulations and experiments have been performed to find the splicing plane. Finally, the accuracy of fabrication can be improved from 10 to about 1 mum; thus, the coupling loss due to the fabrication process can be reduced.     

Robust real-time ship detection and tracking for visual surveillance of cage aquaculture

This paper presents a visual surveillance scheme for cage aquaculture that automatically detects and tracks ships (intruders). For ship detection and tracking, we propose a robust foreground detection and background updating to effectively reduce the influence of sea waves. Furthermore, we propose a fast 4-connected component labeling method to greatly reduce the computational cost associated with the conventional method. Wave ripples are removed from regions with ships. An improved full search algorithm based on adaptive template block matching with a wave ripple removal is presented to quickly, accurately, and reliably track overlapping ships whose scales change. Experimental results demonstrate that the proposed schemes have outstanding performance in ship detection and tracking. The proposed visual surveillance system for cage aquaculture triggers an alarm if intruders are detected. The security of cage aquaculture can be increased. The proposed visual surveillance can thus greatly help the popularization of cage aquaculture for ocean farming.     

非平行分层等离子体鞘套电波传播的复射线方法

基于损耗媒质的复Snell定律提出采用复射线方法研究电磁波在非均匀且非平行分层的等离子体媒质中的传播特性.该方法考虑非均匀平面电磁波的复射线(包括等幅度面的传播射线和等相位面的传播射线), 追踪电磁波复射线在每层媒质中的传播路径以及它们透过媒质分界面时的折射射线, 同时根据复射线的传播方向计算电磁波在每层媒质中的传播衰减, 数值累计整个传播过程中的传播衰减即可获得电磁波穿过等离子体鞘套的总衰减.由钝锥体仿真流场数据简化出非平行分层几何模型并采用复射线方法进行计算分析.计算结果表明:飞行器头部至尾部的传播衰减相差巨大且呈现迅速减小趋势, 非平行分层非均匀等离子体媒质存在某特定入射角, 能使传播衰减达到最小值.     

Mirror synthesis in a mechatronic system for superficial defect detection

This paper deals with the problem of defect detection on highly reflective surfaces making use of vision systems. A new mechatronic system has been developed, based on a nonflat mirror. According to the method described in this paper, the light rays emitted from a source hit a suitably designed nonflat mirror, and are reflected so as to illuminate the curved surface under investigation. The path of the light rays from the source of light to the mirror and then to the object surface is mathematically traced making use of the optical geometry laws. After the reflection on the object surface, the light rays are collected by a charge-coupled device (CCD) camera and elaborated by a vision system, which manages to detect the surface defects as shadows of various shape and size within the picture. Simulations have been carried out in order to provide the optimal mirror shape. Moreover, a prototype of the mechatronic system, including the synthesized mirror, has been built to perform some experimental tests to validate the method. The results, reported in the paper, definitively show the effectiveness of the proposed method.     

基于结构光标记的光场三维成像技术研究

由于四维光场数据中记录了场景中所有光线的方向和强度,通过对其分析和计算即可获得空间场景中对应点的3D坐标。但是目前对光场数据进行处理所采用的重聚焦和多目视觉方法,由于空间场景中特征较少,导致很难确定光场数据中的对应关系光线,因此,重建获得的3D数据不仅稀疏而且精度较低。针对此,提出了一种使用结构光投影技术对三维场景进行标记,并根据相位标记精确的建立起光线之间的对应信息,最终快速地计算出空间场景3D数据的方法。由于4D光场矩阵中存储的是光线相位而不是传统方法中的强度,并且还记录有不同方向的光线信息,因此,该方法不仅提高了传统光场三维重建的精度,还可以解决以往结构光投影三维测量方法中存在的遮挡和高光反射问题。最后通过实验验证了所提方法的可行性和准确性。     

High-frequency multiple diffraction by a flat strip: Higher order asymptotics

By including correction terms in inverse powers of the wavenumberk, one may hope to extend the range of applicability of multiple edge diffracted geometrical theory of diffraction (GTD) to lower frequencies, and also to extend thereby the range of validity of the corresponding time domain solutions. The correction can be applied to each of the surface rays in the hierarchy that has been proposed by us recently as a model for multiple interaction between parallel edges separated by a plane surface segment on a two-dimensional perfectly conducting scatterer. The surface rays, which were found to explain the structure of the complex resonances in transient scattering, are excited for each interaction by equivalent line sources, dipole line sources, and their derivatives, with strengths determined from the asymptotic expansion of the edge diffracted field. This procedure is applied in detail toE- andH- polarized plane wave scattering by a perfectly conducting flat strip, up to quadruple diffraction, including consistentO(k^{-2})corrections with respect to the dominant term. The procedure is applied also to generate corrected multiple diffracted individual surface ray fields, which lead to an improved equation for the complex resonances in the "layer" synthesized in the complex frequency plane by a surface ray of a particular order. Inclusion of the low frequency corrections reduces further the already small discrepancy between the ray optically calculated low frequency resonances and those computed numerically by the moment method.     

提高二次监视雷达解码有效性的方法

从某工程的实际背景出发,研究地面二次监视雷达询问机载航管应答机时出现解码错误的原因——多径影响,提出了一种提高地面二次监视雷达解码正确性的方法.通过对应答信号的全译码,动态调整译码幅度一致性参数的方法,仿真分析结果验证了该方法的可行性和有效性.     

A deterministic propagation model for the microcellular environment using multiple two-dimensional planes

A simplified, computationally efficient radio-wave propagation model is proposed for the microcellular environment to calculate the path loss characteristics of the line-of-sight (LOS) and out-of-sight (OOS) paths in rural and urban environments. This method is based on ray-tracing through combined multiple two-dimensional (2D) planes and the use of a proposed non-reaching ray technique based on the uniform theory of diffraction and Fermat's principle. This paper is a generalization of the use of 2D plane models in the mobile environment. Rather than putting effort into predicting the environment, which is the usual practice, we lay emphasis on the way the ray could be traced towards the mobile in a predictive sense which would lead to reduced complexity of ray-tracing execution time without any serious loss of accuracy. We have utilized the predictive nature of reflections and diffractions to model the propagation paths in terms of multiple 2D planes. It is understood that while the rays follow only reflections, be it from buildings or ground, they will traverse in a well defined plane for a given receiver's position. The same is true for diffraction also. Multiple image theory is used to simplify the ray paths for computation. Rural and urban environments are considered as streets of LOS and OOS paths. Path loss characteristics are determined as a function of polarization, base station antenna height and the diffracted field component. Validation of the theoretical curves is achieved by the experimental results to confirm the efficiency of the proposed model.     

基于KD树的射线跟踪法计算飞行器RCS

利用几何光学射线跟踪法对飞行器整体目标雷达散射截面(Radar cross section,RCS)进行估算,假设入射波为高频平面波,传播中符合几何光学定律,将入射波划分为平行入射线进行跟踪并进行口径积分。为减少射线与大型目标表面的求交计算次数,应用了KD树方法的基本原理,将飞行器目标表面划分多层子包围盒,设计了射线与子包围盒及面元遍历求交算法。应用文中方法计算了一种新型无人飞行器的RCS,计算结果与传统的RCS高频估算方法(PO方法)得到的结果以及实测结果进行比对。结果表明,文中方法较传统PO方法更接近实测结果,在飞行器RCS预估方面具有一定的应用价值。     

基于序列图像的阴影检测研究

针对由于入射光的照射,目标阴影与背景有明显的区别,而被当做目标的问题进行了研究。分析了单幅图像的阴影检测方法,提出了序列图像阴影检测方法,建立了序列图像高度测量模型;采用相邻序列图像对应点匹配的约束条件,降低了匹配的复杂度;研究了序列图像的特征点匹配,获得平面目标的高度信息表示;基于阴影的二维表面属性,设计了利用空间三维信息中的高度信息检测阴影的算法,可以对任意形状的阴影进行检测。通过试验表明,该方法简单,适用面广,可以有效地检测阴影。     

Image change detection algorithms: a systematic survey.

Detecting regions of change in multiple images of the same scene taken at different times is of widespread interest due to a large number of applications in diverse disciplines, including remote sensing, surveillance, medical diagnosis and treatment, civil infrastructure, and underwater sensing. This paper presents a systematic survey of the common processing steps and core decision rules in modern change detection algorithms, including significance and hypothesis testing, predictive models, the shading model, and background modeling. We also discuss important preprocessing methods, approaches to enforcing the consistency of the change mask, and principles for evaluating and comparing the performance of change detection algorithms. It is hoped that our classification of algorithms into a relatively small number of categories will provide useful guidance to the algorithm designer.     

采用扩展MRF的红外目标自适应检测方法

针对天基红外监视系统中不同形状目标的联合检测问题,提出基于扩展马尔可夫随机场的自适应目标检测算法。首先分析了天基红外监视系统中的目标特性,在此基础上以典型目标形状为模板,构建了扩展的马尔可夫随机场邻域系统;其次构建了新的马尔可夫势函数,并利用红外图像中背景与目标之间的马尔可夫势差异,将复杂背景中不同形状目标联合检测问题转换为马尔可夫势差异的判别问题,有效解决了马尔可夫随机场理论框架下混合形状目标检测问题。仿真试验结果表明,所提出的算法能够根据目标形状的变化自适应地检测各类目标,并可在不同图像信杂比条件下进行目标检测处理,具有较强的鲁棒性。     

Model-based 2.5-d deconvolution for extended depth of field in brightfield microscopy.

Due to the limited depth of field of brightfield microscopes, it is usually impossible to image thick specimens entirely in focus. By optically sectioning the specimen, the in-focus information at the specimen's surface can be acquired over a range of images. Commonly based on a high-pass criterion, extended-depth-of-field methods aim at combining the in-focus information from these images into a single image of the texture on the specimen's surface. The topography provided by such methods is usually limited to a map of selected in-focus pixel positions and is inherently discretized along the axial direction, which limits its use for quantitative evaluation. In this paper, we propose a method that jointly estimates the texture and topography of a specimen from a series of brightfield optical sections; it is based on an image formation model that is described by the convolution of a thick specimen model with the microscope's point spread function. The problem is stated as a least-squares minimization where the texture and topography are updated alternately. This method also acts as a deconvolution when the in-focus PSF has a blurring effect, or when the true in-focus position falls in between two optical sections. Comparisons to state-of-the-art algorithms and experimental results demonstrate the potential of the proposed approach.     

基于混合结构神经网络的自适应背景模型

本文提出一种基于神经网络的视频中运动目标检测自适应背景模型.对每个像素点(或局部区域)建立一个混合结构的神经网络背景模型,模型由一个4层前馈神经网络组成,输入层接受像素HSV特征,特征层实现特征提取功能,模式层以概率神经网络的方式完成像素属于背景概率的计算,输出层以赢者取胜的方式完成前景背景分类和模式层激活节点选择功能...     

一种基于射线追踪的时变效应模拟方法

本文探讨了自然界广泛存在的时变效应的模拟问题,实现了一种基于射线追踪方法的时变效应渲染方法.该方法使用Surfels技术对模型表面进行重构和设置属性值,从射线源发射出相应属性值的射线,当射线碰撞到模型表面时将射线属性和模型表面元素属性交换.根据模型表面元素值,选取适当的纹理通过相应的纹理技术进行纹理映射,实现模型表面再次渲染,使模型实现时变效应.针对建筑物场景的实验结果验证了该方法的正确性.     

Object detection using multi-resolution mosaic in image sequences

Object detection in image sequences has a very important role in many applications such as surveillance systems, tracking and recognition systems, coding systems and so on. This paper proposes a unified framework for background subtraction, which is very popular algorithm for object detection in image sequences. And we propose an algorithm using spatio-temporal thresholding and truncated variable adaptation rate (TVAR) for object detection and background adaptation, respectively. Especially when the camera moves and zooms in on something to track the target, we generate multi-resolution mosaic which is made up of many background mosaics with different resolution, and use it for object detection. Some experimental results in various environments show that the averaged performance of the proposed algorithm is good.     

3D depth image analysis for indoor fall detection of elderly people

This paper presents a new fall detection method of elderly people in a room environment based on shape analysis of 3D depth images captured by a Kinect sensor. Depth images are pre-processed by a median filter both for background and target. The silhouette of moving individual in depth images is achieved by a subtraction method for background frames. The depth images are converted to disparity map, which is obtained by the horizontal and vertical projection histogram statistics. The initial floor plane information is obtained by V disparity map, and the floor plane equation is estimated by the least square method. Shape information of human subject in depth images is analyzed by a set of moment functions. Coefficients of ellipses are calculated to determine the direction of individual. The centroids of the human body are calculated and the angle between the human body and the floor plane is calculated. When both the distance from the centroids of the human body to the floor plane and the angle between the human body and the floor plane are lower than some thresholds, fall incident will be detected. Experiments with different falling direction are performed. Experimental results show that the proposed method can detect fall incidents effectively.     

Joint moving cast shadows segmentation and light source detection in video sequences

This paper proposes a new method which allows a joint estimation of the light source projection on the image plane and the segmentation of moving cast shadows in natural video sequences. It allows improving the segmentation of moving objects by separating clearly cast shadows from moving objects. The method is based on a shadow model which mainly assumes that the cast shadows are projected on plane and Lambertian surfaces, and that the light source is unique. The moving cast shadows, including the penumbra, are detected using a segmentation method based on a comparison between a reference image and the original one. The light source position is estimated using geometrical relations linking the light source, the object and its cast shadow on the 2-D image plane. This is obtained using a robust temporal filtering method. For each image using the current estimation of the light source position and the video object contours, a cast shadow search area is defined. This reduces the risk of false detections during the segmentation process, and thus allows increasing the detection rate and reducing the false alarm one. Experimental results show that good shadow and object contours and light source locations are obtained with the proposed method even if the theoretical assumptions are not fully valid.     

基于视点图像与EPI特征融合的光场超分辨率

光场（Light Field, LF）成像能同时捕获场景中光线的空间信息和角度信息,应用广泛。然而,它的分辨率受到成像设备硬件以及空间和角度分辨率之间制衡的限制。过低的空间分辨率严重影响了光场图像的质量及其应用。因此,本文充分利用光场特性增强图像细节,提出一种基于视点图像（Viewpoint Image, VI）和极平面图像（Epipolar Plane Image, EPI）特征融合的端到端光场超分辨率方法,能够同时超分辨率所有视点图像。本方法将低分辨率光场图像按照水平和垂直EPI方向堆叠排列,利用三维视点图像堆栈中包含EPI信息的特点,采用双分支结构的3D递减卷积网络处理输入的四维光场数据。这样能够同时对视点图像和EPI信息进行特征提取和融合,充分探索光场的纹理信息及几何一致性。在真实和合成光场数据集上的实验结果均表明,该方法相比现有主流方法不仅在客观指标上具有更好的表现,主观质量上也能保持更好的几何一致性,同时还具有更少的模型参数和更快的执行速度。