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共有20条相似文献,以下是第1-20项 搜索用时 109 毫秒

1.  Realizing variable contrast technique in MRC measuring target using integrating sphere  被引次数:2
   李文娟  齐超  戴景民《中国光学快报(英文版)》,2004年第9期
   In order to realize variable contrast in the minimum resolvable contrast (MRC) measuring target in the visible imaging system, a novel technique is presented, which adopts two integrating spheres to illuminate two sides of target respectively and the different contrasts can be achieved by regulating the luminance in two integrating spheres. This technique can make the contrast be regulated more conveniently. Based on this technique, the MRC measuring device is developed. This device can be used in all kinds of trial fields. The expanded uncertainty of measuring MRC is less than 3%.    

2.  Design and performance of air flow-assisted ionization imaging mass spectrometry system  
   Fei Tang  Yi Chen  Jiu-Ming He  Zhi-Gang Luo  Zeper Abliz  Xiao-Hao Wang《中国化学快报》,2014年第25卷第5期
   The imaging mass spectrometry(IMS) technology has experienced a rapid development in recent years.A new IMS technology which is based on air flow assisted ionization(AFAI) was reported.It allows for the convenient pretreatment of the samples and can image a large area of sample in a single measurement with high sensitivity.The AFAI in DESI mode was used as the ion source in this paper.The new IMS method is named AFADESI-IMS.The adoption of assisted air flow makes the sample pretreatment easy and convenient.An optimization of the distance between the ion transport tube and MS orifice increases the sensitivity of the system.For data processing,a program based on MATLAB with the function of numerical analysis was developed.A theoretical imaging resolution of a few hundred microns can be achieved.The composite AFAI-IMS images of different target analytes were imaged with high sensitivity.A typical AFAI-IMS image of the whole-body section of a rat was obtained in a single analytical measurement.The ability to image a large area for relevant samples in a single measurement with high sensitivity and repeatability is a significant advantage.The method has enormous potentials in the MS imaging of large and complicated samples.    

3.  Transfer color to night vision images  
   Shaoyuan Sun  Zhongliang Jing  Gang Liu  Zhenhua Li《中国光学快报(英文版)》,2005年第3卷第8期
   Natural color appearance is the key problem of color night vision field. In this paper, the color mood of daytime color image is transferred to the monochromic night vision image. This method gives the night image a natural color appearance. For each pixel in the night vision image, the best matching pixel in the color image is found based on texture similarity measure. Entropy, energy, contrast, homogeneity, and correlation features based on co-occurrence matrix are combined as texture similarity measure to find the corresponding pixels between the two images. We use a genetic algorithm (GA) to find the optimistic weighting factors assigned to the five different features. GA is also employed in searching the matching pixels to make the color transfer algorithm faster. When the best matching pixel in the color image is found, the chromaticity values are transferred to the corresponding pixel of the night vision image. The experiment results demonstrate the efficiency of this natural color transfer technique.    

4.  A general truncated regularization framework for contrast-preserving variational signal and image restoration: Motivation and implementation  
   Chunlin Wu  Zhifang Liu  Shuang Wen《中国科学 数学(英文版)》,2018年第61卷第9期
   Variational methods have become an important kind of methods in signal and image restoration—a typical inverse problem. One important minimization model consists of the squared ?_2 data fidelity(corresponding to Gaussian noise) and a regularization term constructed by a potential function composed of first order difference operators. It is well known that total variation(TV) regularization, although achieved great successes,suffers from a contrast reduction effect. Using a typical signal, we show that, actually all convex regularizers and most nonconvex regularizers have this effect. With this motivation, we present a general truncated regularization framework. The potential function is a truncation of existing nonsmooth potential functions and thus flat on(τ, +∞) for some positive τ. Some analysis in 1 D theoretically demonstrate the good contrast-preserving ability of the framework. We also give optimization algorithms with convergence verification in 2 D, where global minimizers of each subproblem(either convex or nonconvex) are calculated. Experiments numerically show the advantages of the framework.    

5.  ON THE SEPARABLE NONLINEAR LEAST SQUARES PROBLEMS  
   Xin Liu  ;Yaxiang Yuan《计算数学(英文版)》,2008年第3期
   Separable nonlinear least squares problems are a special class of nonlinear least squares problems, where the objective functions are linear and nonlinear on different parts of variables. Such problems have broad applications in practice. Most existing algorithms for this kind of problems are derived from the variable projection method proposed by Golub and Pereyra, which utilizes the separability under a separate framework. However, the methods based on variable projection strategy would be invalid if there exist some constraints to the variables, as the real problems always do, even if the constraint is simply the ball constraint. We present a new algorithm which is based on a special approximation to the Hessian by noticing the fact that certain terms of the Hessian can be derived from the gradient. Our method maintains all the advantages of variable projection based methods, and moreover it can be combined with trust region methods easily and can be applied to general constrained separable nonlinear problems. Convergence analysis of our method is presented and numerical results are also reported.    

6.  Feature-based fusion of infrared and visible dynamic images using target detection  
   刘从义  敬忠良  肖刚  杨波《中国光学快报(英文版)》,2007年第5期
   We employ the target detection to improve the performance of the feature-based fusion of infrared and visible dynamic images, which forms a novel fusion scheme. First, the target detection is used to segment the source image sequences into target and background regions. Then, the dual-tree complex wavelet transform (DT-CWT) is proposed to decompose all the source image sequences. Different fusion rules are applied respectively in target and background regions to preserve the target information as much as possible. Real world infrared and visible image sequences are used to validate the performance of the proposed novel scheme. Compared with the previous fusion approaches of image sequences, the improvements of shift invariance, temporal stability and consistency, and computation cost are all ensured.    

7.  Image reconstruction method for laminar optical tomography with only a single Monte-Carlo simulation  
   Mengyu Jia  Shanshan Cui  Xueying Chen  Ming Liu  Xiaoqing Zhou  Huijuan Zhao  Feng Gao《中国光学快报(英文版)》,2014年第12卷第3期
   Laminar optical tomography(LOT)is a new mesoscopic functional optical imaging technique.Currently,the forward problem of LOT image reconstruction is generally solved on the basis of Monte-Carlo(MC)methods.However,considering the nonlinear nature of the image reconstruction in LOT with the increasing number of source positions,methods based on MC take too much computation time.This letter develops a fast image reconstruction algorithm based on perturbation MC(pMC)for reconstructing the absorption or scattering image of a slab medium,which is suitable for LOT or other functional optical tomography system with narrow source-detector separation and dense sampling.To calculate the pMC parameters,i.e.,the path length passed by a photon and the collision numbers experienced in each voxel with only one baseline MC simulation,we propose a scheme named as the trajectory translation and target voxel regression(TTTVR)based on the reciprocity principle.To further speed up the image reconstruction procedure,the weighted average of the pMC parameters for all survival photons is adopted and the region of interest(ROI)is extracted from the raw data to save as the prior information of the image reconstruction.The method is applied to the absorption reconstruction of the layered inhomogeneous media.Results demonstrate that the reconstructing time is less than 20 s with the X-Y section of the sample subdivided into 50×50 voxels,and the target size quantitativeness ratio can be obtained in a satisfying accuracy in the source-detector separations of 0.4 and 1.25 mm,respectively.    

8.  Image reconstruction tomography with only a method for laminar optical single Monte-Carlo simulation  
   贾梦宇  崔姗姗  陈雪影  刘明  周晓青  赵会娟  高峰《中国光学快报(英文版)》,2014年第3期
   Laminar optical tomography (LOT) is a new mesoscopic functional optical imaging technique. Currently, the forward problem of LOT image reconstruction is generally solved on the basis of Monte-Carlo (MC) methods. However, considering the nonlinear nature of the image reconstruction in LOT with the increasing number of source positions, methods based on MC take too much computation time. This letter develops a fast image reconstruction algorithm based on perturbation MC (pMC) for reconstructing the absorption or scattering image of a slab medium, which is suitable for LOT or other functional optical tomography system with narrow source-detector separation and dense sampling. To calculate the pMC parameters, i.e., the path length passed by a photon and the collision numbers experienced in each voxel with only one baseline MC simulation, we propose a scheme named as the trajectory translation and target voxel regression (TT&TVR) based on the reciprocity principle. To further speed up the image reconstruction procedure, the weighted average of the pMC parameters for all survival photons is adopted and the region of interest (ROI) is extracted from the raw data to save as the prior information of the image reconstruction. The method is applied to the absorption reconstruction of the layered inhomogeneous media. Results demonstrate that the reconstructing time is less than 20 s with the X - Y section of the sample subdivided into 50 × 50 voxels, and the target size quantitativeness ratio can be obtained in a satisfying accuracy in the source-detector separations of 0.4 and 1.25 mm, respectively.    

9.  Novel image fusion method based on discrete fractional random transform  
   郭擎  刘树田《中国光学快报(英文版)》,2010年第7期
   We introduce a new spectrum transform into the image fusion field and propose a novel fusion method based on discrete fractional random transform (DFRNT). In DFRNT domain, high amplitude spectrum (HAS) and low amplitude spectrum (LAS) components carry different information of original images. For different fusion goals, different fusion rules can be adopted in HAS and LAS components, respectively. The proposed method is applied to fuse real multi-spectral (MS) and panchromatic (Pan) images. The fused image is observed to preserve both spectral information of MS and spatial information of Pan. Spectrum distribution of DFRNT is random and uniform, which guarantees that good information is reserved.    

10.  Objective evaluation of target detectability in night vision color fusion images  
   袁轶慧  张俊举  常本康  许辉  韩亦勇《中国光学快报(英文版)》,2011年第1期
   An evaluation for objectively assessing the target detectability in night vision color fusion images is proposed.On the assumption that target detectability could be modeled as the perceptual color variation between the target and its optimal sensitive background region,we propose an objective target detectability metric in CIELAB color space defined by four color information features:target luminance,region perceptual luminance variation in human vision system,region hue difference,and region chroma difference.Experimental results show that this proposed metric is perceptually meaningful because it corresponds well with subjective evaluation.    

11.  Target tracking in infrared imagery using a novel particle filter  
   王芳林  刘尔琦  杨杰  郁生阳  周越《中国光学快报(英文版)》,2009年第7卷第7期
   To address two challenging problems in infrared target tracking, target appearance changes and unpre- dictable abrupt motions, a novel particle filtering based tracking algorithm is introduced. In this method, a novel saliency model is proposed to distinguish the salient target from background, and the eigenspace model is invoked to adapt target appearance changes. To account for the abrupt motions efficiently, a two- step sampling method is proposed to combine the two observation models. The proposed tracking method is demonstrated through two real infrared image sequences, which include the changes of luminance and size, and the drastic abrupt motions of the target.    

12.  Color fusion of SAR and FLIR images using a natural color transfer technique  被引次数:1
   孙韶媛  敬忠良  李振华  刘刚《中国光学快报(英文版)》,2005年第4期
   Fusion of synthetic aperture radar (SAR) and forward looking infrared (FLIR) images is an important subject for aerospace and sensor surveillance. This paper presents a scheme to achieve a natural color image based on the contours feature of SAR and the target region feature of FLIR so that the overall scene recognition and situational awareness can be improved. The SAR and FLIR images are first decomposed into steerable pyramids, and the contour maps in the SAR image and the region maps in the FLIR image are calculated. The contour and region features are fused at each level of the steerable pyramids. A color image is then formed by transferring daytime color to the monochromic image by using the natural color transfer technique. Experimental results show that the proposed method is effective in providing a color fusion of SAR and FLIR images.    

13.  Holographic imaging of full-color real-existing three-dimensional objects with computer-generated sequential kinoforms  
   郑华东  王涛  代林茂  于瀛洁《中国光学快报(英文版)》,2011年第4期
   We propose a computational method for generating sequential kinoforms of real-existing full-color threedimensional (3D) objects and realizing high-quality 3D imaging.The depth map and color information are obtained using non-contact full-color 3D measurement system based on binocular vision.The obtained full-color 3D data are decomposed into multiple slices with RGB channels.Sequential kinoforms of each channel are calculated and reconstructed using a Fresnel-diffraction-based algorithm called the dynamicpseudorandom-phase tomographic computer holography (DPP-TCH).Color dispersion introduced by different wavelengths is well compensated by zero-padding operation in the red and green channels of object slices.Numerical reconstruction results show that the speckle noise and color-dispersion are well suppressed and that high-quality full-color holographic 3D imaging is feasible.The method is useful for improving the 3D image quality in holographic displays with pixelated phase-type spatial light modulators (SLMs).    

14.  Automatic detection of the belt-like region in an image with variational PDE model  
   李寿涛  李小毛  唐延东《中国光学快报(英文版)》,2007年第5期
   In this paper, we propose a novel method to automatically detect the belt-like object, such as highway, river, etc., in a given image based on Mumford-Shah function and the evolution of two phase curves. The method can automatically detect two curves that are the boundaries of the belt-like object. In fact, this is a partition problem and we model it as an energy minimization of a Mumford-Shah function based minimal partition problem like active contour model. With Eulerian formulation the partial differential equations (PDEs) of curve evolution are given and the two curves will stop on the desired boundary. The stop term does not depend on the gradient of the image and the initial curves can be anywhere in the image. We also give a numerical algorithm using finite differences and present various experimental results. Compared with other methods, our method can directly detect the boundaries of belt-like object as two continuous curves, even if the image is very noisy.    

15.  ON THE COUPLED VIBRATION OF AN IDEAL FLUID WITH A LINEAR ELASTIC STRUCTURE  
   黄争鸣《应用数学和力学(英文版)》,1992年第13卷第10期
   The purpose of this paper is to analyse theoretically and numerieally the coupled vibration of an ideal fiuid with a linear elastie structure.It is proved in the paper that the natural frequencies of the coupled vibration do exist and are all real positive. The paper presents an efficient method to transform a coupled fluid-structure system to the structure with added mass and the ribrational analysis of the former is replaced by the latter in vacuum only. Numerical solution is outlined for the transformed problem and a compact frequecy equation is derived in which fluid variables do not appear. This simplifies the analysis significanily. A convergent proof has been given to guarantee the reliability of the solution. The paper also offers a general algorithm combined with Ritz method, boundary element method, and finite element method to analyse the transformed problem. Based on this algorithm, one can apply a known structural analysing program, with a little modification, to solve many different kinds    

16.  Researches on the measurement of distribution image of radiated noise using focused beamforming  
   HUI Juan  HU Dan  HUI Junying  YIN Jingwei《Chinese Journal of Acoustics》,2008年第27卷第2期
   A method using focused beamforming to measure the distribution image (underwater image) of submarine and surface ship's noise sources is presented. Level linear array can measure the target image on water level, but the multi-path interference of underwater acoustic channel may affect the quality of it. Virtual time reversal mirror and virtual array can both solve the problem very well; they make the image with high resolution.    

17.  Robust color segmentation algorithms in illumination variation conditions  
   蓝金辉  申凯《中国光学快报(英文版)》,2010年第3期
   Changing illumination condition can change the result of image segmentation algorithm and reduce the intelligent recognition rate. A novel color image segmentation method robust to illumination variations is presented. The method is applied to the skin segmentation. Based on the hue preserving algorithm, the method reduces the dimensionality of the red-green-blue (RGB) space to one dimension, while keeping the hue of every pixel unchanging before and after space transformation. In the new color space, the skin color model is established using Gaussian model. Experimental results show that the method is robust to illumination variations, and has low computational complexity.    

18.  A mass-conservative average flow model based on finite element method for complex textured surfaces  
   XIE Yi  LI YongJian  SUO ShuangFu  LIU XiangFeng  LI JingHao  WANG YuMing《中国科学:物理学 力学 天文学(英文版)》,2013年第56卷第10期
   A mass-conservative average flow model based on the finite element method(FEM) is introduced to predict the performances of textured surfaces applied in mechanical seals or thrust bearings.In this model,the Jakobsson-Floberg-Olsson(JFO) boundary conditions are applied to the average flow model for ensuring the mass-conservative law.Moreover,the non-uniform triangular grid is utilized,which can deal with the problem of complex geometric shapes.By adopting the modeling techniques,the model proposed here is capable of dealing with complex textured surfaces.The algorithm is proved correct by the numerical experiment.In addition,the model is employed to gain further insight into the influences of the dimples with different shapes and orientations on smooth and rough surfaces on the load-carrying capacity.    

19.  Specific absorbed fractions of electrons and photons forRad-HUMAN phantom using Monte Carlo method  
   王文  程梦云  龙鹏程  胡丽琴《中国物理 C》,2015年第39卷第7期
   The specific absorbed fractions (SAF) for self- and cross-irradiation are effective tools for the internal dose estimation of inhalation and ingestion intakes of radionuclides. A set of SAFs of photons and electrons were calculated using the Rad-HUMAN phantom, which is a computational voxel phantom of a Chinese adult female that was created using the color photographic image of the Chinese Visible Human (CVH) data set by the FDS Team. The model can represent most Chinese adult female anatomical characteristics and can be taken as an individual phantom to investigate the difference of internal dose with Caucasians. In this study, the emission of mono-energetic photons and electrons of 10 keV to 4 MeV energy were calculated using the Monte Carlo particle transport calculation code MCNP. Results were compared with the values from ICRP reference and ORNL models. The results showed that SAF from the Rad-HUMAN have similar trends but are larger than those from the other two models. The differences were due to the racial and anatomical differences in organ mass and inter-organ distance. The SAFs based on the Rad-HUMAN phantom provide an accurate and reliable data for internal radiation dose calculations for Chinese females.    

20.  An algorithm for computed tomography image reconstruction from limited-view projections  
   王林元  李磊  闫镔  江成顺  王浩宇  包尚联《中国物理 B》,2010年第19卷第8期
   <正>With the development of the compressive sensing theory,the image reconstruction from the projections viewed in limited angles is one of the hot problems in the research of computed tomography technology.This paper develops an iterative algorithm for image reconstruction,which can fit most cases.This method gives an image reconstruction flow with the difference image vector,which is based on the concept that the difference image vector between the reconstructed and the reference image is sparse enough.Then the l2-norm minimization method is used to reconstruct the difference vector to recover the image for flat subjects in limited angles.The algorithm has been tested with a thin planar phantom and a real object in limited-view projection data.Moreover,all the studies showed the satisfactory results in accuracy at a rather high reconstruction speed.    

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