3-D face recognition method based on optimum 3-D image measurement technology

Most face recognition systems employ 2-D color or gray-scale images. However, face recognition based on 2-D images is adversely affected by 3-D movement, variable lighting, and the use of cosmetics. 3-D image measurement technology has the potential to overcome these limitations of face recognition based on 2-D images since it can perform geometric analysis. We propose a method that is capable of recognizing a person from a 3-D facial image obtained using a 3-D shape measurement system by employing a technique that optimizes the intensity-modulation pattern projection. This face recognition method is based on the iterative closest point algorithm. It is robust to changes in reflectivity and color. Since the 3-D facial information can be registered, this method can estimate rotations and translations to compensate for different positions or directions. In order to prove the validity of the proposed technique, a verification experiment was conducted which used 105 sample 3-D images obtained from 15 subjects. It achieved a detection rate of 96% when heads were turned at an angle of 20° or less relative to the camera.     

3-D image measurement of the sea for disaster prevention

To reduce the loss of human life in disasters, we have developed an early warning system for typhoons and tsunamis. The system is designed to monitor the change of the sea level from a distance of 20 km. And it can alert a coming tsunami 20 min before reaching the coast. Now, GPS Buoys and observation networks are used to forecast tsunami. However, the GPS buoys are not conducive to monitoring wide ranges of the sea. The observation networks have the disadvantages of high installation costs and difficult maintenance. In this paper, a measurement system of long distance sea level height for disaster prevention has been constructed based on a 3-D image measurement technique. First, to monitor a wide range of the sea surface, this system utilizes the pan and tilt stages and angle sensors to rotate the cameras. To improve the accuracy of long distance 3-D image measurement, a long-distance calibration method of camera system has been proposed based on the scale poles. In addition, all the equipment can be put in one place so it is very convenient to maintain. In this experiment, a dynamic threshold method is proposed in blocks to extract the waves automatically, accompanied by a wave feature matrix matching method in two long-distance images. Finally, the average value of wave height is used as the height of sea level. As a practical use result, a comparison has been made between the measurement results and the data of Japan Meteorological Agency (JMA).     

基于VTK的医学图像交互式三维测量技术研究

VTK是国外开发的集计算机图形.图像处理和可视化于一体的工具开发包,具有高度的灵活性、可移植性.提出一种使用VTK类库实现三维拾取的方法,能够将用户指定的屏幕坐标转化为三维物体坐标系下的空间坐标.最后通过牙齿模型的三维测量实验,证明这种方法具有良好的交互性和实时性.     

A high-speed and continuous 3D measurement system

A new system for high-speed and continuous 3D measurement is presented. It is based on the slit-ray projection method. The key component is the image plane constructed by a position-sensitive device (PSD) array that is horizontally un segmented and linear, but vertically numbered. All PSD row elements are attached to their respective analog signal processors. The analog signals are multiplexed and digitized by multiplexers and A/D converters at appropriate sampling intervals and stored in memory. By virtue of this configuration of the image plane, basis data for 3D measurement are acquired during only one scan of the slit ray at high speed in the form of memory addresses and data. Moreover, if we use large capacity and/or dual port memories, we can continuously obtain 3D range data for as many scenes as needed. The trial system has been implemented with a newly designed 128-channel PSD array and has verified our method, enabling us to obtain successive 3D range data at video rates with an error within±0.3%.     

基于图像的树木测量方法

树木是城市绿化、美化的一个重要的组成部分,具有重要的科学、历史和观赏价值。传统的树木生长信息采集方式,利用人工使用卷尺或不易操作、低效率和复杂麻烦的大型测量仪器等,费时、费力、准确度又不高。结合计算机视觉、数学几何模型等技术,设计了一种新式的树木高度、胸径和冠幅测量模型,提出了基于图像的树木测量方法和实现了树木信息采集软件系统;为了得到更精确的测量结果,使用摄像头标定技术和坐标校正方法对图像进行畸变矫正;并且利用正交试验分析法分析本设计使用的最佳拍摄环境,最终相对误差控制在4%左右。本方法具有携带方便、操作简单、适用面广、准确度高的优势。     

基于三维拼接技术的三维测量系统的开发

提出一种利用参考底座对三维数据进行剪裁拼接的新方法并应用于360°三维全场测量.通过对测量算法、控制软件、云台以及计算机串口通信的系列研究,开发出相应的程序和控制硬件,最终建立了采用面结构光照明的、自动化的360°三维形貌测量系统.该系统给工业三维全场测量提供了一个可操作平台,精确度也达到了实用要求.     

A method for registration of 3-D shapes

The authors describe a general-purpose, representation-independent method for the accurate and computationally efficient registration of 3-D shapes including free-form curves and surfaces. The method handles the full six degrees of freedom and is based on the iterative closest point (ICP) algorithm, which requires only a procedure to find the closest point on a geometric entity to a given point. The ICP algorithm always converges monotonically to the nearest local minimum of a mean-square distance metric, and the rate of convergence is rapid during the first few iterations. Therefore, given an adequate set of initial rotations and translations for a particular class of objects with a certain level of `shape complexity', one can globally minimize the mean-square distance metric over all six degrees of freedom by testing each initial registration. One important application of this method is to register sensed data from unfixtured rigid objects with an ideal geometric model, prior to shape inspection. Experimental results show the capabilities of the registration algorithm on point sets, curves, and surfaces     

A VLSI system architecture for high-speed radiative transfer 3D image synthesis

In this paper we describe a VLSI system architecture for high-speed synthesis of 3D images composed of diffusely reflective surfaces. The system consists of two loosely coupled sub-systems. The first sub-system computes the form-factor matrixF. The form-factors are computed by an efficient ray-tracing algorithm. The second sub-system, a multiprocessor Gauss-Seidel iterative system solver, solves the sparse system of radiosity equations(I–F)b=e.This work has been supported by the Dutch National Applied Science Foundation under grant STW DEL 47.0643This article is the second part of the Special Feature onGraphics Hardware, guest-edited by T. Nakamura. (For the first part, see The Visual Computer 4:175–221)     

3-D imaging systems and high-speed processing for robot control

Bin picking by a robot in real time requires the performance of a series of tasks that are beyond the capabilities of commercially available state-of-the-art robotic systems. In this paper, a laser-ranging sensor for real-time robot control is described. This sensor is incorporated into a robot system that has been applied to the bin-picking or random-parts problem. This system contains new technological components that have been developed recently at the Environmental Research Institute of Michigan (ERIM). These components (the 3-D imaging scanner and a recirculating cellular-array pipeline processor) make generalized real-time robot vision a practical and viable technology. This paper describes these components and their implementation in a typical real-time robot vision system application.     

非规则三维数据的曲面拟合方法

给出了一种非规则三维数据的曲面拟合方法,该方法给出的网络模型不需要删除奇异数据,从而可以保持数据信息的完整性,此外,该方法给出的拟合曲面平滑,连续性好,局部细节丰富,且处处可偏导。     

面向高速数码印花机的实时图像数据转置方法

针对PC无法实时按位转置大量图像数据而限制了数码印花机输出带宽和喷印速度的问题,设计了基于PowerPC处理器和Virtex-5系列FPGA的高速数据处理系统,运用FPGA实现了高效转置运算。为FPGA例化三个独立的DDR2控制器,通过控制器间的协同工作提高系统输出带宽;设计按位转置单元,将图像数据分块转置,利用DDR2控制器的突发传输高效地读写数据。性能测试结果表明FPGA的输出带宽高达327 Mb/s,数码印花机的喷印速度达249 m2/h,相比PC处理系统,在同等条件下性能提升明显。     

A 3-D visualization method for image-guided brain surgery

This paper deals with a 3D methodology for brain tumor image-guided surgery. The methodology is based on development of a visualization process that mimics the human surgeon behavior and decision-making. In particular, it originally constructs a 3D representation of a tumor by using the segmented version of the 2D MRI images. Then it develops an optimal path for the tumor extraction based on minimizing the surgical effort and penetration area. A cost function, incorporated in this process, minimizes the damage surrounding healthy tissues taking into consideration the constraints of a new snake-like surgical tool proposed here. The tumor extraction method presented in this paper is compared with the ordinary method used on brain surgery, which is based on a straight-line based surgical tool. Illustrative examples based on real simulations present the advantages of the 3D methodology proposed here.     

基于图像识别的建筑物三维重建

为从彩色高分辨率的图像中提取出主要建筑物的位置信息并进行三维重建,提出一种结合2D和3-D信息识别建筑物,通过纹理集技术进行大规模3-D重建的方法.进行边缘检测,提取可用的短直线以及相应的2-D特征,对这些短直线进行逐级聚类得到候选屋顶集合;通过朴素贝叶斯分类器在候选屋顶集合中区分出不同的3D屋顶特征,以识别全局优秀的屋顶;根据屋顶的位置信息,在大规模的3-D场景中绘制出相应尺寸的模型,通过动态分配算法将建筑物纹理合并,减少纹理数量,从而减少纹理状态的切换.以航拍和卫星遥感彩色高分辨率图像进行实验,实验结果表明,该方法有优秀的识别正确率和3-D重建效果.     

工业CT图像的亚像素级面积测量

为了提高工业CT图像测量的精度,研究了一种基于Facet模型的亚像素级面积测量方法,并将其应用于实际的工业CT图像测量中。首先采用基于Facet模型的边缘检测算法提取亚像素边缘,然后通过最小距离搜索法分离出待测目标的边缘点并排序,最后利用离散化的格林公式计算面积。其中,基于Facet模型的边缘检测算法精度高、抗噪声能力强,能为后续基于边缘的测量提供高精度的数据;最小距离搜索法在浮点型边缘点上实现了待测目标边缘与整幅图像边缘的分离,并生成排序链码,克服了边缘点是浮点型且不连续的困难,给面积的计算提供了有效的数据。测量方法是在亚像素边缘上进行的,突破了图像分辨率对测量精度的限制,使在低分辨率的图像上实现高精度的测量成为可能。分别针对仿真图像和实际的工业CT图像进行了实验,实验结果表明该方法的测量精度高于普遍采用的像素累加法。     

基于Kinect深度图像的三维重建

随着机器视觉理论的发展和硬件技术的进步,三维重建在生产、生活中的应用越来越广泛,基于Kinect传感器的三维重建得到广泛的应用。针对于现有的Kinect传感器获得的深度图像深度信息丢失的问题,提出了一种新的基于均值滤波的方法对深度图像进行去噪,并对深度图像进行预处理,获取三维点云,用迭代最近点(Iterative Closest Point,ICP)算法完成点云的精确配准,从而得到配准后物体表面三维点云,并完成物体的三维重建。     

应用于CMOS图像传感器的高速列级ADC

提出了一种应用于CMOS图像传感器中的高速列级ADC。采用单斜ADC与TDC结合的方法,先将模拟电压信号转换为成比例的时间段,再通过TDC量化为相应的数字码,其转换时间主要取于TDC的量化范围,解决传统列级单斜ADC转换速率低的问题。设计采用0.18μm CMOS工艺。Spectre仿真表明,在模拟电路3.3 V、数字电路1.8 V的供电电压下,ADC的信噪失真比(SNDR)达到51.2 dB,整体功耗为1.76 mW,列级电路功耗为236.38μW,采样频率为1 MS/s,输入信号范围为1.6 V,满足CMOS图像传感器系统的应用要求。     

3-D motion estimation in model-based facial image coding

An approach to estimating the motion of the head and facial expressions in model-based facial image coding is presented. An affine nonrigid motion model is set up. The specific knowledge about facial shape and facial expression is formulated in this model in the form of parameters. A direct method of estimating the two-view motion parameters that is based on the affine method is discussed. Based on the reasonable assumption that the 3-D motion of the face is almost smooth in the time domain, several approaches to predicting the motion of the next frame are proposed. Using a 3-D model, the approach is characterized by a feedback loop connecting computer vision and computer graphics. Embedding the synthesis techniques into the analysis phase greatly improves the performance of motion estimation. Simulations with long image sequences of real-world scenes indicate that the method not only greatly reduces computational complexity but also substantially improves estimation accuracy     

Detecting 3-D motion field from range image sequences

An algorithm for computing three-dimensional (3-D) velocity field and motion parameters from a range image sequence is presented. It is based on a new integral 3-D rigid motion invariant feature-the trace of a 3x3 "feature matrix" related to the moment of inertia tensor. This trace can be computed at every point of a moving surface and provides a quantitative measure of the local shape of the surface. Based on the feature's conservation along the trajectory of every moving point, a 3-D Flow Constraint Equation is formulated and solved for the velocity field. The robustness of the feature in presence of noise and discontinuity is analyzed.