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1.
辐射成像中射线源低频震动对图像影响的研究   总被引:1,自引:0,他引:1  
对一种大型辐射成像系统-TCM-SCAN系统成像过程中射线源震动的影响进行建模,从理论上对这种影响进行分析,得出射线源震动给图像带来的噪声是乘法性,并确定了噪声频谱特性。同时设计了验证噪声特性的实验,理论与实验符合。在此基础上设计了消除这种噪声的方法。  相似文献   

2.
《核技术》2015,(9)
衍射增强成像是一种功能强大的相位衬度成像技术,其信息分离研究一直都是研究热点。提出了一种简便的信息分离方法——余弦曲线拟合法(Cosine Fitting Radiography,CFR),该方法具有简便、样品所受辐射剂量低等优点。利用同步辐射实验和蒙特卡罗仿真方法,从角度信号成像模型出发解释了此方法,同时从噪声传递角度分析了该方法的性能和给出定量的评价指标,建立了衍射增强成像和光栅微分干涉成像之间更直观的联系。对理解衍射增强成像系统的噪声行为和提高信噪比具有一定的参考意义。  相似文献   

3.
通过分析当前航空辐射监测的不足与缺陷,提出了一种“无人机+热点成像”的航测新思路,并结合γ相机的性能特点,探讨了一种基于γ相机的航空辐射监测方法及其系统装置。空中三维γ成像监测系统将γ辐射成像技术与航空辐射监测技术结合起来,与数据传输系统、地面测控站一起构成航空辐射监测系统,实现空中辐射监测和定位,并在多种情况下取得了良好的应用效果。  相似文献   

4.
低噪声,数字化,集成度高的数据采集系统是当今辐射成像测量中的关键技术之一,针对这些要求提出了一种不同传统的阻容反馈式的前置放大器电路形式。  相似文献   

5.
对薄层结构的复合材料及多层电路板进行密度分布情况及分层成像的研究,是无损检测技术的一个重要应用领域,提出了一种新的成像方法,在现有微焦点X辐射成像系统的基础上,采用一种特殊的摆动式扫描方式,基于非线性的重建成像算法,具有扫描速度快,算法简单,实时性高等特点,适合于多层大面积复合材料以及多层电路板的快速成像检测。  相似文献   

6.
辐射成像中的图像由于具有很大的统计噪声,因而较难被压缩,本文提出了两种适用于辐射图像的压缩方法。文章中描术字算法的原理和具体步骤,并提供了一些实验结果。  相似文献   

7.
在现有微焦点X光辐射成像系统的基础上 ,提出一种新的摆动式分层成像方法 ,对狭长形状薄层结构样品进行无损检测 ,建立计算机仿真模型 ,验证了使用不完全投影的合理性和高效率 ,讨论了不完全投影中投影区域的选择原则。实际成像结果表明 :分布在最佳投影区域的 1 2 0°投影可成功地分离出印制电路板不同层次的图像  相似文献   

8.
介绍了一种由阵列式数字化γ辐射探头组成的钍矿石选矿在线测量系统。探测器采用NaI(Tl)晶体,通过脉冲放大、滤波成形和单道脉冲幅度甄别等电路输出数字矩形脉冲,构成单路数字化γ辐射探头。钍矿石依次经过十路探头,探头产生的脉冲计数和作为矿石筛选依据,由FPGA实现十路计数器、求取计数和以及与上位机串行通信,上位机软件采用Python语言编写,具有实时显示钍矿石含量、异常报警、参数调整和输出保存等功能。经测试,系统运行稳定可靠,可满足实际工作需要。  相似文献   

9.
在现有微焦点X光辐射成像系统的基础上,提出一种新的摆动式分层成像方法,对狭长形状薄层结构样品进行无损检测,建立计算机仿真模型,验证了使用不完全投影的合理性和高效率,讨论了不完全投影中投影区域的选择原则.实际成像结果表明分布在最佳投影区域的120°投影可成功地分离出印制电路板不同层次的图像.  相似文献   

10.
《同位素》2008,21(4)
【公开日】2008.07.02【分类号】G01N23/04【公开号】CN101210894【申请日】2006.12.30【申请号】200610171577.4【申请人】同方威视技术股份有限公司;清华大学【文摘】本发明涉及辐射成像检查和放射性物质监测技术领域。本发明提供一种可同时进行辐射成像检查和放射性物质监测的系统及方法。该系统包括辐射成像检查子系统和放射性物质监测子系  相似文献   

11.
TJ-II Thomson Scattering diagnostic provides temperature and density profiles of plasma. The CCD camera acquires images that are corrupted with some kind of noise called stray-light. This noise degrades both image contrast and measurement accuracy, which could produce unreliable profiles of the diagnostic. So far, several approaches have been applied in order to decrease the noise in the TJ-II Thomson scattering images. Since the presence of the noise is not global but located in some particular regions of the image, advanced processing techniques are needed. However such methods require of manual fine-tuning of parameters to reach a good performance. In this contribution, an iterative image processing approach is applied in order to reduce the stray light effects in the images of the TJ-II Thomson scattering diagnostic. The proposed solution describes how the noise can be iteratively reduced in the images when a key parameter is automatically adjusted during the iterative process.  相似文献   

12.
速调管走廊泄漏电磁噪声的模拟计算与对比测试   总被引:1,自引:0,他引:1  
陶小平  王贵诚 《核技术》2001,24(6):491-496
为确定泄漏噪声源的特性及位置,对国家同步辐射实验室速调管走廓泄漏电磁噪声进行了模拟计算,给出了调制器高频泄漏噪声的计算方法和计算公式。在模拟计算的基础上进行了现场的对比测试,对比测试结果显示了模拟计算的合理性,从而为抑制走廓的噪声泄漏提供了理论基础。  相似文献   

13.
速调管走廊抗干扰技术研究   总被引:2,自引:0,他引:2  
合肥国家同步辐射实验室速调管走廓内存在着高频电磁泄漏,为确保走廓内的通讯信号不被干扰,采用抗干扰技术对泄漏噪声进行了抑制,并对抑制前后的泄漏噪声作了对比测试,结果显示了所采用的抗干扰技术的有效性。  相似文献   

14.
One contrast parameter which can be used to form images in scanning transmission ion microscopy (STIM) is the energy loss of individual transmitted ions. This paper explores three techniques which can be used if energies of several ions are measured at each incident beam location. The techniques are energy averaging, summing of events within a preset energy window, and median filtering of energy values. Median filtering is the method of choice to reduce noise and to sharpen certain features. Examples of line scans of a sharp edge and of a ramp-like knife edge are presented. With median filtering localization of features to within 10% of beam size is demonstrated. A mechanism for identifying and mapping unresolved spatial structure is proposed. The other techniques are shown to be better tools for beam-profile diagnostics.  相似文献   

15.
The expectation maximization (EM) algorithm for the maximum likelihood (ML) image reconstruction criterion generates severe checkerboard artifacts in the presence of noise. A classical remedy is to impose an a priori constraint for a penalized ML or maximum a posteriori probability solution. The penalty reduces the checkerboard artifacts and also introduces uncertainty because a priori information is usually unknown in clinic. Recent theoretical investigation reveals that the noise can be divided into two components: one is called null-space noise and the other is range-space noise. The null-space noise can be numerically estimated using filtered backprojection (FBP) algorithm. By the FBP algorithm, the null-space noise annihilates in the reconstruction while the range-space noise propagates into the reconstructed image. The aim of this work is to investigate the relation between the null-space noise and the checkerboard artifacts in the ML-EM reconstruction from noisy projection data. Our study suggests that removing the null-space noise from the projection data could improve the signal-to-noise ratio of the projection data and, therefore, reduce the checkerboard artifacts in the ML-EM reconstructed images. This study reveals an in-depth understanding of the different noise propagations in analytical and iterative image reconstructions, which may be useful to single photon emission computed tomography, where the noise has been a major factor for image degradation. The reduction of the ML-EM checkerboard artifacts by removing the null-space noise avoids the uncertainty of using a priori penalty.  相似文献   

16.
Neutron noise induced by propagating disturbances in VVER-type reactor core is addressed in this paper. The spatial discretization of the governing equations is based on the box-scheme finite difference method for triangular-z geometry. Using the derived equations, a 3-D 2-group neutron noise simulator (called TRIDYN-3) is developed for hexagonal-structured reactor core, by which the discrete form of both the forward and adjoint reactor dynamic transfer functions (in the frequency domain) can be calculated. In addition, both types of noise sources, namely point-like and traveling perturbations, can be modeled by TRIDYN-3. The results are then benchmarked in different cases. Considering the noise source as propagating perturbations of the macroscopic absorption cross sections, the induced neutron noise is calculated throughout the reactor core. For the first time, adjoint approach is applied and examined for modeling moving noise sources. Moreover, the space- and frequency-dependence of the propagation noise are investigated in this paper.  相似文献   

17.
应用蒙特卡罗模拟软件GATE对GeDiscoveryLSPET/CT扫描系统进行模拟,获得三维投影数据,分别采用三维有序子集最大期望值法(3-DOSEM)与三维滤波反投影法(3-DFBP)进行图像重建,从空间分辨率、成像的对比度以及信噪比等方面对3-DOSEM法与3-DFBP法的重建结果进行比较。结果显示,对蒙特卡罗方法模拟获得的三维投影数据,采用3-DOSEM法重建比3-DFBP法重建得到的图像质量好。  相似文献   

18.
逆动态方法是一种有效的实时反应性测量方法,此方法实现的关键是准确地计算中子信号的导数和积分,导数对于测量信号中的噪声很敏感,而噪声是不可避免的。论文研究了几种降低噪声影响的方法,包括低通滤波器和平滑样条函数的方法,并进行了数值仿真,证明平滑样条函数能有效地消除测量信号中的噪声,直至5%信噪比的信号都能取得较好的结果,并且不产生延迟。因此,消除噪声的算法是逆动态方法实现的一个关键基础,平滑样条函数是一个较好的选择。  相似文献   

19.
In this paper, we review some of the possibilities for digital enhancement of Computed Tomography (CT) images. The basic hypothesis is that the array of computed x-ray absorbtion values obtained in CT contains more information than the unaided eye can generally grasp. Examples of novel contrast enhancement and noise smoothing algorithms are included to support this hypothesis. Particular attention is paid to properties of the human visual system which we consider an element of the overall information processing loop.  相似文献   

20.
Ultrasound Vibration Potential signals (UVP) are generated when an ultrasound wave traverses colloidal suspensions or ionic solutions and disturbs their electrical equilibrium. The potential can be measured as an electrical signal and provides information that can be used to determine characteristics of the sample. The reverse effect, where an electrical signal in a colloidal suspension generates an ultrasonic signal also occurs and is commonly termed the Electro Sonic Amplitude (ESA). Measured amplitudes of UVP signals are in the region of a few hundred nano-volts and micro-volts and therefore pose difficulties in obtaining consistent data. Low noise instrumentation and techniques are necessary to obtain reliable measurements. UVP techniques have already been used to measure sample characteristics in homogenous distributions. However the technique also shows a high contrast between different types of object samples and can be used as an imaging method. This work describes the initial instrumentation and sensing methods that have been developed for detecting UVP signals for the purpose of imaging applications and the results with laboratory phantoms.  相似文献   

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