共查询到19条相似文献,搜索用时 875 毫秒
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为了解决视频传输中整帧图像丢失的误差扩散问题,提出了一种基于多参考帧运动矢量外推的整帧丢失错误掩盖算法.通过对多个参考帧的运动矢量外推得到丢失块的候选运动矢量集|采用多参考帧边界匹配准则进行丢失帧和其后续帧的误差估计,并选择丢失块的最优运动矢量|最后采用自适应的重叠块运动补偿方法重建丢失帧.实验结果表明,该算法在恢复整帧图像的同时,有效地降低了视频序列中整帧图像丢失的误差扩散影响,与已有算法比较,该算法恢复的视频序列平均峰值信噪比提高了0.5~1 dB,具有更好的错误掩盖效果. 相似文献
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双随机相位图像加密的实值编码研究 总被引:7,自引:5,他引:2
提出了一种基于双随机相位的图像实值编码方法,该方法可应用于光学图像加密.要编码的纯相位图像分别在空间域和频域加入随机相位掩膜,其中在频域将编码范围扩大4倍,经过光学系统的变换,将生成的图像取实部作为编码图像.实值编码的图像利用与编码过程类似的方法进行解码,可以准确地重建原图像.该编译码方法简单,编码图像是一个近似随机噪声的实值图像,便于数字图像的传输与输出. 相似文献
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相机阵列是获取空间中目标光场信息的重要手段,采用大规模密集相机阵列获取高角度分辨率光场的方法增加了采样难度和设备成本,同时产生的大量数据的同步和传输需求也限制了光场采样规模.为了实现稀疏光场采样的稠密重建,本文基于稀疏光场数据,分析同一场景多视角图像的空间、角度信息的关联性和冗余性,建立有效的光场字典学习和稀疏编码数学模型,并根据稀疏编码元素间的约束关系,建立虚拟角度图像稀疏编码恢复模型,提出变换域稀疏编码恢复方法,并结合多场景稠密重建实验,验证提出方法的有效性.实验结果表明,本文方法能够对场景中的遮挡、阴影以及复杂的光影变化信息进行高质量恢复,可以用于复杂场景的稀疏光场稠密重建.本研究实现了线性采集稀疏光场的稠密重建,未来将针对非线性采集稀疏光场的稠密重建进行研究,以推进光场成像在实际工程中的应用. 相似文献
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为了解决视频流在不可靠网络上的错误传播问题,使用基于帧的多描述视频编码,提出采用预测的预处理和后处理过程方案,实现了描述间的冗余插入|实现了几种不同复杂度,不同性能的错误掩盖算法以适应多样化的网络传输环境.仿真实验结果表明,这种编码系统能有效控制视频流的错误传播,并且编码后的数据流更能适应各种网络传输状况. 相似文献
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磁共振成像扫描过程中如果在K空间中出现尖峰噪声,将会严重影响图像质量. 该文提出了一种利用磁共振图像背景信息来定位并修复尖峰噪声的方法. 首先将K空间数据沿着频率编码kx和相位编码ky 2个方向分别进行一维傅立叶变换,然后在获得的2个中间域数据中,分别截取出背景区域, 进行一维反傅立叶变换得到与背景对应的频率域数据,通过对背景频率域数据的分析,获得尖峰噪声的kx和ky坐标,最后对异常点进行修复. 该算法可以很好地消除各种模式的尖峰噪声,与已有的算法相比,能够更好地处理K空间中连续多个相位编码行上出现尖峰噪声的情况,有效地消除图像伪影. 相似文献
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针对激光反射断层成像过程中存在目标的平动和抖动所产生的旋转中心偏移导致重建图像错位形成伪影的问题,提出基于相位恢复技术的改进误差下降算法.该方法通过光强反复迭代得到相位分布,获得重构目标丢失的相位信息,通过增加初始约束条件以及空间域和频域的限制有效改善算法的收敛性.运用改进的误差下降算法,有效改善了相位恢复方法容易陷入局部极小解的问题,获得了优化的重构图像.仿真实验表明,三组投影数据重建图像的平均相对均方误差由0.774下降为0.551,能够有效消除图像重建伪影.外场实验结果表明此方法使激光反射断层成像系统分辨率得到有效改善. 相似文献
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Pang Y Xie Z Xu D Kelley DA Nelson SJ Vigneron DB Zhang X 《Magnetic resonance imaging》2012,30(2):290-298
In this work, an eight-element by eight-element dual-tuned quadrature volume coil with a mix of capacitor terminated half-wavelength (λ/2) and quarter-wavelength (λ/4) microstrip resonators is proposed for multinuclear magnetic resonance imaging/spectroscopy studies at 7 T. In the proton channel, λ/2 microstrip resonators with capacitive terminations on both ends are employed for operation at higher frequency of 298.1 MHz; in the heteronucleus channel, capacitor-terminated λ/4 resonators, suitable for low frequency operations, are used to meet the low frequency requirement. This mixed structure design is particularly advantageous for high field heteronuclei magnetic resonance applications with large difference in Larmor frequency of the nuclei in question. The proposed design method makes it much easier to perform frequency tuning for heteronucleus channel using a variable capacitor with a practical capacitance range. As an example, a dual-tuned volume coil for (1)H/(13)C mouse spectroscopic imaging was proposed to demonstrate the feasibility of this method. The finite-difference time-domain method is first used to model this dual-tuned volume coil and calculate the B(1) field distributions at two frequencies. Transmission parameters (S(21)) measured between the proton channel and the carbon channel are -50 dB at 75 MHz and -35 dB at 298 MHz, showing the excellent isolation between the two channels at 7 T. The proton image and (13)C FIDCSI image of a corn oil phantom on the axial plane at 7 T demonstrate the feasibility of the proposed method. A preliminary proton image of a mouse on the sagittal plane is also acquired using the proposed dual-tuned volume coil at 7 T, illustrating a fairly uniform B(1) field and sufficient image coverage for imaging in mice. 相似文献
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为解决广义相干系数用于合成孔径成像中所存在的运算量大,图像对比度改善有限等问题,提出空间广义相干系数加权成像方法。该算法根据单个孔径成像结果之间的相干性来计算相干系数,通过加权空间合成进行成像。采用对FieldⅡ仿真点目标和吸声斑目标的数据进行成像表明,算法不仅使运算量减少N(N为阵元数)倍,而且相对于传统的广义相干系数算法,算法对散射点成像可提高信噪比7 dB,对于吸声斑成像可提高对比度3.2 dB。可见算法可以有效地提高成像速度和成像质量。 相似文献
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PurposeSingle image super-resolution (SR) is highly desired in many fields but obtaining it is often technically limited in practice. The purpose of this study was to propose a simple, rapid and robust single image SR method in magnetic resonance (MR) imaging (MRI).MethodsThe idea is based on the mathematical formulation of the intrinsic link in k-space between a given (modulus) low-resolution (LR) image and the desired SR image. The method consists of two steps: 1) estimating the low-frequency k-space data of the desired SR image from a single LR image; 2) reconstructing the SR image using the estimated low-frequency and zero-filled high-frequency k-space data. The method was evaluated on digital phantom images, physical phantom MR images and real brain MR images, and compared with existing SR methods.ResultsThe proposed SR method exhibited a good robustness by reaching a clearly higher PSNR (25.77dB) and SSIM (0.991) averaged over different noise levels in comparison with existing edge-guided nonlinear interpolation (EGNI) (PSNR=23.78dB, SSIM=0.983), zero-filling (ZF) (PSNR=24.09dB, SSIM=0.985) and total variation (TV) (PSNR=24.54dB, SSIM=0.987) methods while presenting the same order of computation time as the ZF method but being much faster than the EGNI or TV method. The average PSNR or SSIM over different slice images of the proposed method (PSNR=26.33 dB or SSIM=0.955) was also higher than the EGNI (PSNR=25.07dB or SSIM=0.952), ZF (PSNR=24.97dB or SSIM=0.950) and TV (PSNR=25.70dB or SSIM=0.953) methods, demonstrating its good robustness to variation in anatomical structure of the images. Meanwhile, the proposed method always produced less ringing artifacts than the ZF method, gave a clearer image than the EGNI method, and did not exhibit any blocking effect presented in the TV method. In addition, the proposed method yielded the highest spatial consistency in the inter-slice dimension among the four methods.ConclusionsThis study proposed a fast, robust and efficient single image SR method with high spatial consistency in the inter-slice dimension for clinical MR images by estimating the low-frequency k-space data of the desired SR image from a single spatial modulus LR image. 相似文献
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为获取高帧频、大动态范围、低数据量的精确视觉信息,提出了一种基于地址-事件表达(AER)的实时视觉CMOS传感器实现方法。采用AER方式,多模式的行仲裁及实时时间标记,有效减小读出数据量,减小时域行间信息扭曲;利用像素级光强变化感知电路探测光强变化,双采样脉冲宽度调制(PWM)电路量化光强。仿真结果显示,在100lx光强下,获得最小等效帧频1000frame/s,10lx光强下为100frame/s,静态动态范围大于133dB,视频动态范围48.16dB,并可实现实时时间标记、多模式仲裁的功能,减小输出数据量11.61%~42.74%。结果表明,该方法可完成实时视觉信息的采集、处理、输出,适用于高速、高动态范围视觉领域。 相似文献
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Noriaki Suetake Hideaki Kawano Go Tanaka Hidenobu Hashikami Eiji Uchino 《Optical Review》2011,18(6):423-429
In this paper, a new image enlargement method applying the backprojection for lost pixel (BPLP) to the predefined codebook-based
method is proposed. BPLP is a method for image restoration. In BPLP, the eigenspace reflecting the characteristics of an input
image is generated from the remained pixels and is used to restore the missing pixels. In the proposed method, the eigenspace
is replaced by one generated from the predefined codebook (PDC). PDC represents edge-blurring properties in a small image
patch and consists of pairs of low- and high-frequency image patches on various edge patterns. By replacing the PDC-based
estimation of lost high-frequency components with BPLP, a fast image enlargement method retaining its performance can be developed.
Through some experiments, the effectiveness of the proposed method was demonstrated. Especially, it was confirmed that the
processing time of the proposed method was shortened to about 1/50 that of the PDC-based method. 相似文献
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随着光学成像到光电数字成像的转变,如何提高CCD的几何分辨率已成为研制高分辨光电成像系统亟待解决的问题。从研究现状入手,给出了现有算法并指出不足之处`,建立了亚像元超分辨成像数学模型,提出了亚像元的CCD几何超分辨方法:将两片线阵CCD集成在同一器件中,在线阵方向上错开半个像元,同时读出时间减半,最终交织重组图像数据,合成高分辨率图像。利用MATLAB软件对双线性插值方法及亚像元成像方法进行了仿真,并定性定量地分析了两种方法的效果。结果表明:亚像元方法合成图像分辨率约为低分辨率图像的2倍,且两组仿真图像中的峰值信噪比比双线性插值图像分别高出1.4864dB和2.2070dB,该方法可以显著地减轻欠采样引起的图像模糊,且实时性优于双线性插值方法。 相似文献
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提出了分组Karhunen-Leove变换(KLT)和整数小波变换(IWT)的高光谱图像数据压缩方法,并采用整数小波变换技术和Set Partitioning in Hierarchical Trees(SPIHT)压缩编码,实现了对分组Karhun-Loeve变换后的数据压缩。该压缩编码方法与现有压缩方法相比,既保留了Karhun-Loeve变换压缩性能和整数小波变换高压缩比的特点,也宜于实时传输。实验结果表明,分组Karhun-Loeve变换/整数小波变换/SPIHT在相同压缩比下,峰值信噪比比Karhun-Loeve变换/小波变换/WSFCVQ、Karhun-Loeve变换/小波变换/改进的对块零树编码压缩和Karhun-Loeve变换/WT/FSVQ分别提高了6 dB,9 dB和8 dB,运算时间减少一半,整体压缩性能有了较大的提高。 相似文献
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为了在现有的采样条件下,通过新的压缩采样方式获得计算量小且质量更好的图像,提出了基于压缩感知与扩展小波树的自适应压缩成像方法。首先将图像投影到分区控制的DMD上,获得图像在低分辨率下的测量值,并通过压缩感知重构算法重构出低分辨图像,接着利用扩展小波树预测重要小波位置,通过DMD在小波域采样获取图像的细节信息,最后由小波逆变换恢复高分辨率图像。将该方法与最小化全变分算法(TVAL3)和近来提出的基于扩展小波树的自适应成像算法(EWT-ACS)效果进行对比,实验结果表明,以boat图像为例,在压缩感知采样率为0.75,整体采样率为10%的无噪声条件下,该方法相较于TVAL3、EWT-ACS算法信噪比提高了4.63 dB和2.87 dB,在附加噪声条件下成像效果也较好。该方法能极大地降低压缩感知重建算法的运行时间,同时减少采样次数,具有较好的抗噪性。 相似文献