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1.
从明暗恢复形状(SFS)的几类典型算法分析与评价   总被引:29,自引:3,他引:26       下载免费PDF全文
从明暗恢复形状(shape from shading,简称SFS)是计算机视觉中三维形状恢复问题的关键技术之一,其任务是利用单幅图象中物体表面的明暗变化来恢复其表面三维形状。为了使人们对SFC研究现状及求解SFS问题的各种算法的优缺点有个概略了解,首先介绍了求解传统SFS问题的4类方法中几个典型算法的基本原理及求解方法,并给出了实验结果,然后从算法解的唯一性、对真解的逼近程度、求解效率及适用范围等方面对这4类算法进行了比较和评价。  相似文献
2.
由单目图像获得表面高度算法的分析和实现   总被引:10,自引:0,他引:10  
由单目图像获得物体表面高度(由阴影恢复形状)是计算机视觉中的一个翻来覆去研究领域,迭代计算算法的准确度在合成图像的表面恢复上得到了验证,在遥感图像的表面高度提取中也得到了应用,文中对一种新的由单目图像忧愁物体表面高度和梯度的算法进行了详细分析,并提出了实现算法的具体步骤和计算方法,对合成图像进行迭代计算,区 准确的表面高度,对实际焊点图像也验证了该算法的可行性。  相似文献
3.
一种基于单幅图像的树木深度估计与造型方法   总被引:9,自引:0,他引:9  
提出了种基于单幅图像、利用光照引起的明暗效果(shading)恢复树木枝干三维形态的方法,与传统shape from shading技术相比,该方法根据树木的特殊结构,利用更稳定的明暗特征,取消了对表面、光源及拍摄条件的限制,从而将算法的鲁棒性提高到足以处理自然的树木照片.基于上述工作,提出了一种基于单幅照片的交互式树木造型方法,该方法避免用数学模型控制树木形态,独立于树木的具体种类,具有较高的普  相似文献
4.
Generalization of the Lambertian model and implications for machine vision   总被引:8,自引:0,他引:8  
Lambert's model for diffuse reflection is extensively used in computational vision. It is used explicitly by methods such as shape from shading and photometric stereo, and implicitly by methods such as binocular stereo and motion detection. For several real-world objects, the Lambertian model can prove to be a very inaccurate approximation to the diffuse component. While the brightness of a Lambertian surface is independent of viewing direction, the brightness of a rough diffuse surface increases as the viewer approaches the source direction. A comprehensive model is developed that predicts reflectance from rough diffuse surfaces. The model accounts for complex geometric and radiometric phenomena such as masking, shadowing, and interreflections between points on the surface. Experiments have been conducted on real samples, such as, plaster, clay, sand, and cloth. All these surfaces demonstrate significant deviation from Lambertian behavior. The reflectance measurements obtained are in strong agreement with the reflectance predicted by the proposed model. The paper is concluded with a discussion on the implications of these results for machine vision.  相似文献
5.
基于阴影的三维表面重构技术的概述   总被引:6,自引:2,他引:4  
三维表面重构是计算机视觉的主要任务之一。已经发展了各种各样的重构技术,其中利用单幅图像中物体表面明暗变化来恢复其表面形状的技术尤其引人注目,这不仅因为该技术简单易于实现,更重要的是它适用于各种其它方法难以应用的场合,例如,在机栽、星栽、弹载环境中的利用。论文从SFS问题的研究背景出发,介绍并分析这方面的一些重要进展,通过对各种重构方法的分析与比较,提出SFS问题的研究发展趋势和一些值得研究的方向.  相似文献
6.
In this paper we present provably convergent algorithms for the linear and nonlinear Shape from Shading problem in the case of a Lambertian reflectance map. For the linear problem we discuss two explicit methods and one implicit method, for which we prove convergence for certain light directions. The method for the nonlinear Shape from Shading problem is based on a linear approximation of the image irradiance equation. For the resulting linear PDE the implicit method for the linear problem can be applied. We prove convergence of this method for all light directions.  相似文献
7.
In this paper, a supervised self-organisation Neural Network (NN) for direct shape from shading is developed. The structure of the NN for the inclined light source model is derived based on the maximum uphill direct shape from shading approach. The major advantage of the NN model presented is the parallel learning or weight evolution for the direct shading. Here the proved convergent learning rule, the rate of convergence and a zero initialisation condition are shown. To increase the rate of convergence, the momentum factor is introduced. Further-more, the application of the network on IC (Integrated Circuit) component shape reconstruction is presented.  相似文献
8.
Seafloor map generation for autonomous underwater vehicle navigation   总被引:3,自引:0,他引:3  
Elevation map generation is an essential component of any autonomous underwater vehicle designed to navigate close to the seafloor because elevation maps are used for obstacle avoidance, path planning and self localization. We present an algorithm for the reconstruction of elevation maps of the seafloor from side-scan sonar backscatter images and sparse bathymetric points co-registered within the image. Given the trajectory for the underwater vehicle, the reconstruction is corrected for the attitude of the side-scan sonar during the image generation process. To perform reconstruction, an arbitrary but computable scattering model is assumed for the seafloor backscatter. The algorithm uses the sparse bathymetric data to generate an initial estimate for the elevation map which is then iteratively refined to fit the backscatter image by minimizing a global error functional. Concurrently, the parameters of the scattering model are determined on a coarse grid in the image by fitting the assumed scattering model to the backscatter data. The reconstruction is corrected for the movement of the sensor by initially doing local reconstructions in sensor coordinates and then transforming the local reconstructions to a global coordinate system using vehicle attitude and performing the reconstruction again. We demonstrate the effectiveness of our algorithm on synthetic and real data sets. Our algorithm is shown to decrease the average elevation error when compared to real bathymetry from 4.6 meters for the initial surface estimate to 1.6 meters for the final surface estimate from a survey taken of the Juan de Fuca Ridge.  相似文献
9.
基于阴影恢复形状的起皱织物表面形态重建研究   总被引:3,自引:0,他引:3  
阴影恢复形状算法是计算机视觉中的一个重要研究课题 ,该算法应用于织物三维表面重建 ,为客观评价织物起皱等级奠定了基础 .提出了一种新的阴影恢复重建算法 ,并阐述了该算法的实现步骤和计算方法 .先利用合成图象对算法进行迭代计算并验证 ,获得了较为准确的重建图象 ,然后再结合真实模板进行重建 ,重建准确度较高 .同时说明了该算法可应用于真实织物的表面重建之中 ,并可从获得的织物三维轮廓数据中提取特征值 ,实验表明 ,这些特征值均可从不同侧面表征织物的褶皱程度 ,特征值与织物的褶皱程度基本呈线性相关  相似文献
10.
Shape-from-Shading Under Perspective Projection   总被引:3,自引:0,他引:3  
Shape-from-Shading (SfS) is a fundamental problem in Computer Vision. A very common assumption in this field is that image projection is orthographic. This paper re-examines the basis of SfS, the image irradiance equation, under a perspective projection assumption. The resultant equation does not depend on the depth function directly, but rather, on its natural logarithm. As such, it is invariant to scale changes of the depth function. A reconstruction method based on the perspective formula is then suggested; it is a modification of the Fast Marching method of Kimmel and Sethian. Following that, a comparison of the orthographic Fast Marching, perspective Fast Marching and the perspective algorithm of Prados and Faugeras on synthetic images is presented. The two perspective methods show better reconstruction results than the orthographic. The algorithm of Prados and Faugeras equates with the perspective Fast Marching. Following that, a comparison of the orthographic and perspective versions of the Fast Marching method on endoscopic images is introduced. The perspective algorithm outperformed the orthographic one. These findings suggest that the more realistic set of assumptions of perspective SfS improves reconstruction significantly with respect to orthographic SfS. The findings also provide evidence that perspective SfS can be used for real-life applications in fields such as endoscopy.This research has been supported in part by Tel-Aviv University fund, the Adams Super-Center for Brain Studies, the Israeli Ministry of Science, the ISF Center for Excellence in Applied Geometry, the Minerva Center for geometry, and the A.M.N. fund.  相似文献
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