共查询到19条相似文献,搜索用时 109 毫秒
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由于光在水中传输时的衰减和散射效应,使得光学成像细节丢失、对比度下降以及颜色偏移失真,导致水下图像雾化。因此在光线条件较为恶劣情况下,水下高性能相机对目标的有效捕捉范围较小,水下光学成像系统通常很难达到令人满意的成像效果。而声呐利用声波在水中传播衰减较小的特点可以进行更远距离的探测。因此,当水下目标距离光学探测设备较远而不能进行准确光学成像来捕捉目标时,可利用声呐采集得到的信息与光学图像进行融合,实现图像增强,提高成像效果。文章提出了一种基于声呐信息融合的水下图像增强方法,首先对水下光学图像分两步进行预处理,即基于暗通道先验模型的去雾增强和自适应图像增强,再使用声呐信息对水下图像进行局部增强,明显提高水下环境中所要探测目标的对比度与可识别度。 相似文献
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针对复杂海洋环境中声呐探测弱目标易被强干扰淹没的问题,提出一种对被动声呐探测到的强干扰源进行跟踪抑制的方法,通过对观测数据的互谱密度矩阵(Cross Spectral Density Matrix,CSDM)进行特征分解,根据干扰方位范围的先验知识,对干扰源的方位进行跟踪,依据方位信息选择代表强干扰的特征向量,依此根据不同的算法重构剔除了干扰信息的CSDM。数值仿真和海试数据验证结果表明,该方法能够在已知干扰初始方位区域的情况下自适应地抑制强干扰,较好地保留并提取目标信息,检测出感兴趣的目标。该方法为后续的目标识别与跟踪提供了有利条件。 相似文献
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为研究和分析用仿生信号及处理方法探测沉底小目标的可行性及探测性能,分别从时域频域波形、模糊度函数、抗混响性能方面分析了仿海豚声呐信号,并用计算机仿真了复杂背景下沉底小目标的探测。理论分析和仿真结果表明:在几种仿海豚声呐信号中,频率重叠较多的信号混响抑制效果最好;仿生探测方法的性能比标准声呐探测方法有了明显的提高。仿生信号及探测方法可作为一种新型的沉底小目标探测信号及处理方法。 相似文献
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以提取得到的被动声呐目标功率谱特征为基础,采用二进制粒子群(Binary Particle Swarm Optimization, BPSO)优化算法和k最近邻(k-Nearest Neighbor, KNN)分类算法相结合的BPSO-KNN算法进行特征选择和参数优化,分别用KNN分类算法和BPSO-KNN分类算法对实际得到的四类海上被动声呐目标进行分类识别。结果表明,BPSO-KNN算法可对提取的功率谱特征进行特征优化选择,并对KNN分类器进行参数优化,提高了对四类目标的分类精度。该算法在被动声呐目标分类识别方面有参考价值。 相似文献
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水下小目标精细成像对于正确识别水下目标具有重要意义。目前,多波束成像声呐和条带合成孔径声呐是获取水下小目标图像的主要手段。水下目标的判别主要利用了目标图像的亮点特征,即使是同一目标从不同方位观测时得到的结果也可能差异较大,这给快速识别确认目标带来了困难。为解决该问题,提出了利用圆周合成孔径声呐对水下小目标进行水声层析成像信号处理方法,提高了声呐的多角度融合观测能力。仿真及试验数据处理结果表明,合成孔径声呐层析成像方法能够获得目标外形轮廓精细特征,有利于水下小目标的正确识别。 相似文献
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利用合成孔径声呐可以获得高分辨力地貌或目标成像,在合成孔径基础上进一步采用分裂阵相位相干测高方法可以获得地貌或目标的三维成像。分析论证合成孔径中分裂阵相位相干测高的原理,在影响测高误差的诸多参数中着重针对相位差测量的因素进行了分析,并进行了仿真研究。仿真研究结果表明:利用小尺度合成孔径声呐进行三维成像的测高精度可达到目标水平距离的1%。 相似文献
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三维数据场可视化的算法及实现 总被引:2,自引:0,他引:2
本文介绍了科学计算可视化的核心问题——三维数据场可视化(volu-me visualisation)的基本算法,并以CT扫描医学图像的三维重构及三维流场的可视化为例,讨论了绘制三维场的面表达及体直接表达算法的实现问题,文中还给出了算法实现中的实验结果。 相似文献
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为验证密集式多输入多输出(Multi-Input Multi-Output,MIMO)声呐高分辨成像算法的有效性,进行了水池实验并获得了期望的高分辨成像结果。首先,将成像算法分为角度维高分辨成像和距离维高分辨成像两种,分别建立了各自的成像处理流程。角度维高分辨成像基于虚拟阵列波束形成算法,距离维高分辨成像基于大带宽信号合成算法。然后,根据两种处理流程选择合适的发射信号和阵型,并据此搭建密集式MIMO声呐高分辨成像平台进行水池实验。最后,通过与传统单输入多输出(Single-Input Multi-Output,SIMO)声呐的成像结果进行对比,证明了MIMO声呐可结合发射信号、阵型和相应的处理流程获得更高的角度分辨率和距离分辨率。 相似文献
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针对高频成像声呐多目标跟踪中声成像的不稳定问题,在基于检测前跟踪的声呐图像序列尺度不变特征变换(Scale Invariant Feature Transform,SIFT)的基础上,提出了一种结合对数变换的声呐图像序列SIFT特征跟踪方法。该方法利用对数变换进行图像预处理,进而利用声呐图像序列SIFT特征进行多目标跟踪。水池试验数据的处理结果表明:与中值滤波和动态亮度分配的方法相比,结合对数变换的声呐图像序列SIFT特征跟踪方法具有更好的多目标跟踪效果。 相似文献
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SAS测绘率是大面积海底测绘的一个重要指标,多子阵的方法已经在常规单站SAS的实际系统中取得了良好的效果。针对双站合成孔径声纳(双站SAS)测绘速率受空间降采样率限制的问题,该本文首先给出了发射站固定的双站SAS模型,分析了该模型双站SAS的测绘率。为了提高双站SAS的测绘率,本文中提出了发射站固定下的多子阵双站合成孔径声纳成像方法,并给出了严格的数学模型,形成了多子阵双站SAS系统设计方案,提高了系统的测绘率。文章最后给出了基于波束形成逐点算法多子阵双站SAS的成像仿真,仿真结果验证了方法的有效性。 相似文献
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Theoretical analysis of three-dimensional imaging and recognition of micro-organisms with a single-exposure on-line holographic microscope 总被引:1,自引:0,他引:1
Stern A Javidi B 《Journal of the Optical Society of America. A, Optics, image science, and vision》2007,24(1):163-168
Single-exposure on-line (SEOL) digital holography is a recently proposed technique for monitoring, visualization, and recognition of three-dimensional (3D) objects. In contrast to traditional multi-exposure on-line digital holography, it uses only one exposure, which makes it particularly suitable for imaging and recognizing moving micro-organisms. However, the cost of using only one exposure is the superposition of a conjugate image on the desired reconstructed image. The influence of the conjugate image on the visualization and recognition performance is investigated. The conditions for which the cross-talk noise induced by the conjugate image is negligible are derived. It is demonstrated that with conditions common in imaging of microscopic 3D biological objects, SEOL digital holography is highly tolerant of cross-talk noise induced by the conjugate image. 相似文献
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Wenxue Zhang Jianbo Jian Cuiyun Sun Jie Chen Wenjuan Lv Mengyu Sun Yuqing Zhao Qi Zhao Chunhong Hu 《International journal of imaging systems and technology》2020,30(2):464-472
Gliomas are rich in blood vessels, and the generation of tumor-associated vessels plays an important role in glioma growth and transfer. Histology can directly depict microvascular architecture in the tumor, but it just provides two-dimensional (2D) images obtained by destroying three-dimensional (3D) tissue specimens. There is a lack of high-resolution 3D imaging methods for observing the microvasculature throughout the entire specimens. X-ray phase-contrast computed tomography (PCCT) which is an emerging imaging method has demonstrated its outstanding potential in imaging soft tissues. Thus, this study aims to evaluate the potential of PCCT as an adjunct to histopathology in nondestructive and 3D visualization of the microvascular architecture in human glioma tissues. In this study, seven resected glioma tissues were scanned via PCCT and then processed histologically. The obtained PCCT data was analyzed and compared with corresponding histological results. Significant anatomical structures of the glioma such as microvessels, thrombi inside the microvessels, and areas of vascular proliferation could be clearly presented via PCCT, confirmed by the histological findings. Moreover, PCCT data also provided additional 3D information such as morphological alterations of the microvasculature, 3D distribution of the thrombi and stenosis severity of the vessels in glioma tissues, which cannot be fully analyzed in 2D histological slices. In conclusion, this study demonstrated that PCCT can offer excellent images at a near-histological level and additional valuable information in screening gliomas, without impeding further histological investigations. Thus, this technique could be potentially used as an adjunct to conventional histopathology in 3D nondestructive characterization of glioma vasculature. 相似文献
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Stepinski T 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2007,54(7):1399-1408
A new implementation of a synthetic aperture focusing technique (SAFT) based on concepts used in synthetic aperture radar and sonar is presented in the paper. The algorithm, based on the convolution model of the imaging system developed in frequency domain, accounts for the beam pattern of the finite-sized transducer used in the synthetic aperture. The 2D fast Fourier transform (FFT) is used for the calculation of a 2D spectrum of the ultrasonic data. The spectrum is then interpolated to convert the polar coordinate system used for the acquisition of ultrasonic signals to the rectangular coordinates used for the presentation of imaging results. After compensating the transducer lobe amplitude profile using a Wiener filter, the transformed spectrum is subjected to the 2D inverse Fourier transform to get the time-domain image again. The algorithm is computationally attractive due to the use of 2D FFT. The performance of the proposed frequency-domain algorithm and the classical time-domain SAFT are compared in the paper using simulated and real ultrasonic data. 相似文献
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Jian-Fei Chai Xiao-Mei Hu He-Wei Qu Ming-Hang Li Hui-Jing Xu Yu Liu Tao Yu 《先进制造进展(英文版)》2018,6(1):126-135
New production line management technologies are required and adopted recently with the development of modern manufacturing industry. In this study, a production line three-dimensional (3D) visualization monitoring system based on OpenGL modeling, open database connectivity (ODBC), and database management technology is established on a VC++6.0 platform to satisfy effective production. A client/server model is adopted in the system, and data on processing information, interactive operation, and failure process are stored in the server side database. A client reads the workpiece process information from the server, and the machining process of every workpiece is visually represented in the form of 3D visualization. Production line 3D visualization provides production capacity simulation to optimize the parameter settings. When compared with the analysis results of production line capacity, the key parameters possess the same optimal values, and this proves the accuracy of production line 3D visualization monitoring system. The system provides effective data support for production line monitoring and management in enterprises.
The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0217-x 相似文献