Towards 3-D scene reconstruction from broadcast video

Three-dimensional (3-D) scene reconstruction from broadcast video is a challenging problem with many potential applications, such as 3-D TV, free-view TV, augmented reality or three-dimensionalization of two-dimensional (2-D) media archives. In this paper, a flexible and effective system capable of efficiently reconstructing 3-D scenes from broadcast video is proposed, with the assumption that there is relative motion between camera and scene/objects. The system requires no a priori information and input, other than the video sequence itself, and capable of estimating the internal and external camera parameters and performing a 3-D motion-based segmentation, as well as computing a dense depth field. The system also serves as a showcase to present some novel approaches for moving object segmentation, sparse and dense reconstruction problems. According to the simulations for both synthetic and real data, the system achieves a promising performance for typical TV content, indicating that it is a significant step towards the 3-D reconstruction of scenes from broadcast video.     

一种基于时空结合的动态场景立体视频匹配方法

提出了一种基于时空结合的动态场景立体视频匹配方法。通过对连续视频帧的仿射变换运动建模,建立连续帧之间的时域联系,在颜色分割的基础上,根据重叠分割块在连续帧之间视差变化的平滑性约束,利用左右视图之间的几何相关性对视差进行选择性优化,以克服在立体视频逐帧匹配过程中由于颜色分割块的不稳定而导致的误匹配和视差跳变现象,使得最终获取的视差视频在时间轴上更加准确稳定。实验结果表明,算法能有效降低视差视频的跳变现象,对由颜色分割引入的错误匹配也能进行很好的纠正,获取了较为准确的视差视频结果。     

3维的快门使单透镜相机具有立体感

CRL Opto公司(位于英国Middle-sex的Hayes)开发了一种3维图像获取系统。不久就可以整合到一系列单透镜照相机的应用中去。此项技术利用了多单元液晶快门。此快门可以产生适当景深的3维图像。     

从单幅图像恢复立体景象的新方法

在研究单幅平面图像内在特性的基础上,提出了一种恢复立体视觉景象建模的新方法。对图像进行智能识别处理,可以求得许多线段的特征参数,并由此计算出消隐点和消隐线,从而可自动获得场景的立体结构信息。本算法的特点在于用一个代数表达式统一了三种典型的度量方法,无需传统的相机内校正参数,直接可计算出建模用立体信息。建模结果用VRML格式保存、输出,以便于网上浏览。众多的图像验证了该方法的有效性、适用性。     

Spectrum Illumination for 3-D Surface Imaging System

A method using spectrum illumination to reconstruct 3-D object image is a new concept in the field of computer vision. The design of optical illumination system is crucial in this method. Several ways to achieve multi-color spectrum illumination are discussed. A prism illumination system is designed by means of aligning symmetrically the prism at the mid-wavelength (n d=1.806 274) of light path and using reflection collimating lens, cylindrical expending lens and two optical shutters. The relations between deviation angles and light wavelengths are given, and some 3-D reconstruction results are presented.     

Spectrum Illumination for 3— Surface Imaging System

A method using spectrum illumination to reconstruct 3-D bject image is a new concept in the field of computer vision.The design of optical illumination system is crucial this method.Several ways to achieve multicolor spectrum illumination are discussed.A prism illumination system is designed by means of aligning symmetrically the prism at the mid-wavelength(nd=1.806 274)of light path and using reflection collimating lens,cylindrical expending lens and two optical shutters.The relations between deviation angles and light wavelengths are given,and some 3-D reconstruction results are presented.     

2—D Fourier Transform Method for Optical Measurement of 3—D Surface

A emthod of 2-D Fourier transform used in 3-D surface profilometry is proposed,analyzed and compared with 1-D Fourier transform method in theory and practical measuring result.It was proved that the 2-D Fourier transform method has more advantages over 1-D Fourier transform methodd in biggest crook-rate limits,accuracy and sensitivity of measuring.Styudy on measuring object surface details with large crook-rate changing accurately used new higher-power index low-pass filter of spatial frequency domain.A new method of automatic produced reference grating image and error-correcting is proposed.One undeform row of deform grating image is used to extend a complete reference grating image,and some error-correcting method is used to process the result to get accurate surface shape and the deflection of reference surface normal line deviated from the axle of camera.By this new method,one deform rectangle grating image is only used to get the 3-D shape accurately.     

A least-squares-based 2-D filtering scheme for stereo imagecompression

A two-dimensional (2-D) least squares (LS)-based filtering scheme for high fidelity stereo image compression applications is introduced in this correspondence. This method removes the effects of mismatching in a stereo image pair by applying the left image as the reference input to a 2-D transversal filter while the right image is used as the desired output. The weights of the filter are computed using a block-based LS method. A reduced order filtering scheme is also introduced to find the optimum number of filter coefficients. The principal coefficients and the disparity vectors are used together with left image to reconstruct the right image at the receiver, The proposed schemes are examined on a real stereo image pair for 3D-TV applications and the results were benchmarked against those of the block-matching method.     

3-D shape estimation of DNA molecules from stereo cryo-electron micro-graphs using a projection-steerable snake.

We introduce a three-dimensional (3-D) parametric active contour algorithm for the shape estimation of DNA molecules from stereo cryo-electron micrographs. We estimate the shape by matching the projections of a 3-D global shape model with the micrographs; we choose the global model as a 3-D filament with a B-spline skeleton and a specified radial profile. The active contour algorithm iteratively updates the B-spline coefficients, which requires us to evaluate the projections and match them with the micrographs at every iteration. Since the evaluation of the projections of the global model is computationally expensive, we propose a fast algorithm based on locally approximating it by elongated blob-like templates. We introduce the concept of projection-steerability and derive a projection-steerable elongated template. Since the two-dimensional projections of such a blob at any 3-D orientation can be expressed as a linear combination of a few basis functions, matching the projections of such a 3-D template involves evaluating a weighted sum of inner products between the basis functions and the micrographs. The weights are simple functions of the 3-D orientation and the inner-products are evaluated efficiently by separable filtering. We choose an internal energy term that penalizes the average curvature magnitude. Since the exact length of the DNA molecule is known a priori, we introduce a constraint energy term that forces the curve to have this specified length. The sum of these energies along with the image energy derived from the matching process is minimized using the conjugate gradients algorithm. We validate the algorithm using real, as well as simulated, data and show that it performs well.     

Automated 3-D PDM construction from segmented images using deformable models

In recent years, several methods have been proposed for constructing statistical shape models to aid image analysis tasks by providing a priori knowledge. Examples include principal component analysis of manually or semiautomatically placed corresponding landmarks on the learning shapes [point distribution models (PDMs)], which is time consuming and subjective. However, automatically establishing surface correspondences continues to be a difficult problem. This paper presents a novel method for the automated construction of three-dimensional PDM from segmented images. Corresponding surface landmarks are established by adapting a triangulated learning shape to segmented volumetric images of the remaining shapes. The adaptation is based on a novel deformable model technique. We illustrate our approach using computed tomography data of the vertebra and the femur. We demonstrate that our method accurately represents and predicts shapes.     

一种可用于硅刻蚀工艺模拟的三维表面演化算法

针对硅微加工中的刻蚀工艺模拟应用,提出了一种基于点元网格和单位法向最的三维表面演化算法,在形成的连续曲面上,以高斯积分法得到点元步进的单位法向量,实现三维表面的构建与推进.根据典型的刻蚀工艺及其物理模型,该表面演化算法能够用于硅等离子体刻蚀等与表面演化方向相关的工艺模拟.参照简单的各向同性刻蚀,利用该三维算法实现了不同...     

Digital stereo image analyzer for generating automated 3-D measures of optic disc deformation in glaucoma

The major limitations of precise evaluation of retinal structures in present clinical situations are the lack of standardization, the inherent subjectivity involved in the interpretation of retinal images, and intra- as well as interobserver variability. While evaluating optic disc deformation in glaucoma, these limitations could be overcome by using advanced digital image analysis techniques to generate precise metrics from stereo optic disc image pairs. A digital stereovision system for visualizing the topography of the optic nerve head from stereo optic disc images is presented. We have developed an algorithm, combining power cepstrum and zero-mean-normalized cross correlation techniques, which extracts depth information using coarse-to-fine disparity between corresponding windows in a stereo pair. The gray level encoded sparse disparity matrix is subjected to a cubic B-spline operation to generate smooth representations of the optic cup/disc surfaces and new three-dimensional (3-D) metrics from isodisparity contours. Despite the challenges involved in 3-D surface recovery, the robustness of our algorithm in finding disparities within the constraints used has been validated using stereo pairs with known disparities. In a preliminary longitudinal study of glaucoma patients, a strong correlation is found between the computer-generated quantitative cup/disc volume metrics and manual metrics commonly used in a clinic. The computer generated new metrics, however, eliminate the subjective variability and greatly reduce the time and cost involved in manual metric generation in follow-up studies of glaucoma.     

A neural-learning-based reflectance model for 3-D shape reconstruction

In this letter, the limitation of the conventional Lambertian reflectance model is addressed and a new neural-based reflectance model is proposed of which the physical parameters of the reflectivity under different lighting conditions are interpreted by the neural network behavior of the nonlinear input-output mapping. The idea of this method is to optimize a proper reflectance model by a neural learning algorithm and to recover the object surface by a simple shape-from-shading (SFS) variational method with this neural-based model. A unified computational scheme is proposed to yield the best SFS solution. This SFS technique has become more robust for most objects, even when the lighting conditions are uncertain.     

Fault Surface Detection in 3-D Seismic Data

A novel approach to the automatic extraction of geological faults from three-dimensional (3-D) seismic data is described, and qualitative and quantitative comparisons of manually and automatically picked fault geometries interpreted from both high and medium quality 3-D seismic datasets are presented. An algorithm has been developed that allows semiautomated identification, extraction, and modeling of fault surfaces imaged in 3-D seismic datasets. Based on a multistage approach, the algorithm operates initially at a small spatial scale, identifying local discontinuities in the seismic horizons, and then gradually considers larger and larger segments of fault surfaces until a set of complete fault surfaces are identified. A large portion of the work involves merging of segments of fault surfaces, performed using a highest confidence first (HCF) stratagem, taking into consideration the context of the resultant fault geometry. We show that results from the automated fault picker compare favorably with a manually labeled set of faults surfaces interpreted from a high-quality dataset. Last, we present an estimate of the savings in human operator time that can be made by using the automated approach, indicating savings of multiple person-days for the multigigabyte datasets that typify the petroleum industry.     

A geometric model for 3-D confocal image analysis

In this paper, we use partial-differential-equation-based filtering as a preprocessing and post processing strategy for computer-aided cytology. We wish to accurately extract and classify the shapes of nuclei from confocal microscopy images, which is a prerequisite to an accurate quantitative intranuclear (genotypic and phenotypic) and internuclear (tissue structure) analysis of tissue and cultured specimens. First, we study the use of a geometry-driven edge-preserving image smoothing mechanism before nuclear segmentation. We show how this filter outperforms other widely-used filters in that it provides higher edge fidelity. Then we apply the same filter, with a different initial condition, to smooth nuclear surfaces and obtain sub-pixel accuracy. Finally we use another instance of the geometrical filter to correct for misinterpretations of the nuclear surface by the segmentation algorithm. Our prefiltering and post filtering nicely complements our initial segmentation strategy, in that it provides substantial and measurable improvement in the definition of the nuclear surfaces.     

基于偏振双目视觉的无纹理高反光目标三维重构

对于表面光滑、纹理单一甚至缺失、高反光的目标,传统的三维重构方法由于对纹理以及反光特性的依赖会使得重构表面出现大面积的的数据空洞.而基于偏振的三维重构方法不依赖于物体表面的纹理信息,同时偏振成像能够在一定程度上抑制耀光,能够有效解决传统三维重构方法存在的问题.但是,基于偏振视觉的三维重构方法得到的是像素坐标系下的深度信息,因此提出了偏振双目视觉三维重构方法,以由双目立体视觉获得的少量特征点的世界三维坐标为"桥梁",利用双目立体标定得到的相机参数,将偏振得到的图像像素坐标系下的点云数据转化为世界坐标系下的绝对数据.     

An accurate thin-wire model for 3-D TLM simulations

Accurate modeling of thin wires in large-scale numerical electromagnetic simulations is very time consuming if fine meshing is adopted. Special treatments of such wires to allow their incorporation into relatively coarse meshes have lead to the development of thin-wire nodes for the transmission-line matrix (TLM) method. Previous models require the use of empirical factors. A novel thin-wire node is presented that is derived from rigorous field theory, requires no empirical factors and is shown to be highly effective. Moreover, virtually no computational overhead is incurred in the use of the new wire node.     

Reconstruction of 3-D horizons from 3-D seismic datasets

We propose a method for extracting automatically and simultaneously the quasi-horizontal surfaces in three-dimensional (3-D) seismic data. The proposed algorithm identifies connected sets of points which form surfaces in 3-D space. To improve reliability, this algorithm takes into consideration the relative positions of all horizons, and uses globally self-consistent connectivity criteria which respect the temporal order of horizon creation. The first stage of the algorithm consists of the preliminary estimation of the local direction of each horizon at each point of the 3-D space. The second stage consists of smoothing the signal along the detected layer structure to reduce noise. The last stage consists of the simultaneous building of all 3-D horizons. The output of the processing is a set of 3-D horizons represented by a series of triangulated surfaces.     

一种用线阵CCD测量物体表面三维轮廓的新方法

提出了一种用线阵CCD对物体三维轮廓进行测量的新方法,通过矩形光栅离焦投影,产生正弦光场,利用线阵CCD对物体进行扫描采样,采用三步相移技术进行相位解调,对物体三维轮廓进行测量,重点分析讨论了用线阵CCD对物体三维轮廓进行测量的原理和特性,并给出了试验简图及实际测量结果。