Improvement of Binocular Reconstruction Algorithm for Measuring 3D Pavement Texture Using a Single Laser Line Scanning Constraint

The dense and accurate measurement of 3D texture is helpful in evaluating the pavement function.To form dense mandatory constraints and improve matching accuracy,the traditional binocular reconstruction technology was improved threefold.First,a single moving laser line was introduced to carry out global scanning constraints on the target,which would well overcome the difficulty of installing and recognizing excessive laser lines.Second,four kinds of improved algorithms,namely,disparity replacement,superposition synthesis,subregion segmentation,and subregion segmentation centroid enhancement,were established based on different constraint mechanism.Last,the improved binocular reconstruction test device was developed to realize the dual functions of 3D texture measurement and precision self-evaluation.Results show that compared with traditional algorithms,the introduction of a single laser line scanning constraint is helpful in improving the measurement’s accuracy.Among various improved algorithms,the improvement effect of the subregion segmentation centroid enhancement method is the best.It has a good effect on both overall measurement and single pointmeasurement,which can be considered to be used in pavement function evaluation.

Stereo particle image velocimetry measurement of 3D soil deformation around laterally loaded pile in sand

A developed stereo particle image velocimetry(stereo-PIV) system was proposed to measure three-dimensional(3D) soil deformation around a laterally loaded pile in sand.The stereo-PIV technique extended 2D measurement to 3D based on a binocular vision model,where two cameras with a well geometrical setting were utilized to image the same object simultaneously.This system utilized two open software packages and some simple programs in MATLAB,which can easily be adjusted to meet user needs at a low cost.The failure planes form an angle with the horizontal line,which are measured at 27°-29°,approximately three-fourths of the frictional angle of soil.The edge of the strain wedge formed in front of the pile is an arc,which is slightly different from the straight line reported in the literature.The active and passive influence zones are about twice and six times of the diameter of the pile,respectively.The test demonstrates the good performance and feasibility of this stereo-PIV system for more advanced geotechnical testing.

Fast Estimation of Loader’s Shovel Load Volume by 3D Reconstruction of Material Piles

Fast and accurate measurement of the volume of earthmoving materials is of great signifcance for the real-time evaluation of loader operation efciency and the realization of autonomous operation. Existing methods for volume measurement, such as total station-based methods, cannot measure the volume in real time, while the bucket-based method also has the disadvantage of poor universality. In this study, a fast estimation method for a loader’s shovel load volume by 3D reconstruction of material piles is proposed. First, a dense stereo matching method (QORB–MAPM) was proposed by integrating the improved quadtree ORB algorithm (QORB) and the maximum a posteriori probability model (MAPM), which achieves fast matching of feature points and dense 3D reconstruction of material piles. Second, the 3D point cloud model of the material piles before and after shoveling was registered and segmented to obtain the 3D point cloud model of the shoveling area, and the Alpha-shape algorithm of Delaunay triangulation was used to estimate the volume of the 3D point cloud model. Finally, a shovel loading volume measurement experiment was conducted under loose-soil working conditions. The results show that the shovel loading volume estimation method (QORB–MAPM VE) proposed in this study has higher estimation accuracy and less calculation time in volume estimation and bucket fll factor estimation, and it has signifcant theoretical research and engineering application value.

Wheel center detection based on stereo vision

As the location of the wheel center is the key to accurately measuring the wheelbase, the wheelbase difference and the wheel static radius, a high-precision wheel center detection method based on stereo vision is proposed. First, according to the prior information, the contour of the wheel hub is extracted and fitted as an ellipse curve, and the ellipse fitting equation can be obtained. Then, a new un-tangent constraint is adopted to improve the ellipse matching precision. Finally, the 3D coordinates of the wheel center can be reconstructed by the spatial circle projection algorithm with low time complexity and high measurement accuracy. Simulation experiments verify that compared with the ellipse center reconstruction algorithm and the planar constraint optimization algorithm, the proposed method can acquire the 3D coordinates of the spatial circle more exactly. Furthermore, the measurements of the wheelbase, the wheelbase difference and the wheel static radius for three types of vehicles demonstrate the effectiveness of the proposed method for wheel center detection.

双CMOS仿生3D视觉传感器电路设计

针对目前3D相机中出现的图像数据易丢失、左右图像同步难等问题,提出一种可精确采集左右格式立体对图像的仿生3D传感器实现方法,可为仿生3D传感器的光路系统的检验及目标物三维重建提供精确三维坐标信息。为更好协调3D传感器在光信号处理中的点像素同步,采用现场可编程门阵列处理双OV3640图像传感器各信号,初始化后在像素时钟的准确控制下采集图像数据并完成输出图像格式转换、缓存、左右格式立体对图像拼接及输出显示验证。结果表明,3D传感器工作可靠、集成度高、体积小,可精确采集左右格式立体对图像。

单镜头真3D立体摄像技术

针对集成成像技术记录图像呈现立体深度小、图像摄取技术要求高等缺点,提出一种单镜头真3D立体摄像系统,并从系统结构、原理、核心元件参数设计、显示效果等方面对系统进行分析。研究表明,单镜头真3D立体摄像系统能记录并呈现更深的三维场景,且可在一定范围内进行焦距调整,其结构简单,有利于真3D立体图像技术的推广,具有较高的研究与应用价值。

基于3-D打印技术的新型微波/毫米波无源波导器件

综述了近年来基于多种3-D打印工艺的微波直至太赫兹频段无源波导器件的发展研究现状,并介绍了作者所在小组研制的多个基于立体光刻3-D打印工艺的滤波器(包括基于新型高Q值单模和双模球形腔体谐振器的X频段带通滤波器以及基于裂缝波导和紧凑片上结构的W频段带通滤波器).这些滤波器射频性能的测量与仿真结果吻合良好.与相同形状的铜制器件相比,采用非金属材料的3-D打印器件的重量减轻了80%以上,并保持了优良的射频性能.

3-D计算机视觉系统的高精度摄象机定标算法—DLTEAⅡ

本文在分析计算机视觉系统中摄象机几何模型的基础上,修正了光学镜头畸变模型使之与数字成象系统相配合,提出了一个非常适合于3—D计算机视觉系统的通用高精度摄象机定标方法:增强型直接线性变换—误差拟合算法(DLTEAⅡ).实验表明,使用普通CCD摄象机的立体视觉系统经DLTEAⅡ定标后,在300mm×200mm视场和0.8m～0.9m深度范围内其三维定位的绝对精度分别为dx<0.03mm,dy<0.04mm和dz<0.09mm,相对精度为视场大小和深度的1/10000.本文所提出的定标方法在三维计算机视觉、智能机器人、工业自动化生产、近景摄影测量和军事等领域有着广泛的应用前景.

3D视音频技术综述

随着2009年底卡梅隆导演的《阿凡达》影片的热映,三维立体(3D Stereo)显示技术成为目前火热的技术之一,通过左右眼信号分离,在显示平台上能够实现的立体图像显示。立体显示是VR虚拟现实的一个实现沉浸交互的方式之一,3D(3 dimensional)立体显示可以把图像的纵深,层次,位置等细节全部展现,观察者更直观地了解图像的现实分布状况,从而更全面了解图像或显示内容的信息。为了配合3D立体视觉环境,介绍了3D音频技术,它是未来的一个趋势,并且对3D音频技术的基本理论、声学特点和发展状况等给出了看法。

3D Particle Image Velocimetry Test of Inner Flow in a Double Blade Pump Impeller

The double blade pump is widely used in sewage treatment industry,however,the research on the internal flow characteristics of the double blade pump with particle image velocimetry（PIV） technology is very little at present.To reveal inner flow characteristics in double blade pump impeller under off-design and design conditions,inner flows in a double blade pump impeller,whose specific speed is 111,are measured under the five off-design conditions and design condition by using 3D PIV test technology.In order to ensure the accuracy of the 3D PIV test,the external trigger synchronization system which makes use of fiber optic and equivalent calibration method are applied.The 3D PIV relative velocity synthesis procedure is compiled by using Visual C＋＋ 2005.Then absolute velocity distribution and relative velocity distribution in the double blade pump impeller are obtained.Test results show that vortex exists in each condition,but the location,size and velocity of vortex core are different.Average absolute velocity value of impeller outlet increases at first,then decreases,and then increases again with increase of flow rate.Again average relative velocity values under 0.4,0.8,and 1.2 design condition are higher than that under 1.0 design condition,while under 0.6 and 1.4 design condition it is lower.Under low flow rate conditions,radial vectors of absolute velocities at impeller outlet and blade inlet near the pump shaft decrease with increase of flow rate,while that of relative velocities at the suction side near the pump shaft decreases.Radial vectors of absolute velocities and relative velocities change slightly under the two large flow rate conditions.The research results can be applied to instruct the hydraulic optimization design of double blade pumps.

A Skeletal Camera Network for Close-range Images with a Data Driven Approach in Analyzing Stereo Configuration

Structure-from-Motion(SfM)techniques have been widely used for 3D geometry reconstruction from multi-view images.Nevertheless,the efficiency and quality of the reconstructed geometry depends on multiple factors,i.e.,the base-height ratio,intersection angle,overlap,and ground control points,etc.,which are rarely quantified in real-world applications.To answer this question,in this paper,we take a data-driven approach by analyzing hundreds of terrestrial stereo image configurations through a typical SfM algorithm.Two main meta-parameters with respect to base-height ratio and intersection angle are analyzed.Following the results,we propose a Skeletal Camera Network(SCN)and embed it into the SfM to lead to a novel SfM scheme called SCN-SfM,which limits tie-point matching to the remaining connected image pairs in SCN.The proposed method was applied in three terrestrial datasets.Experimental results have demonstrated the effectiveness of the proposed SCN-SfM to achieve 3D geometry with higher accuracy and fast time efficiency compared to the typical SfM method,whereas the completeness of the geometry is comparable.

AVS 3D Video Coding Technology and System

Following the success of the audio video standard （AVS） for 2D video coding, in 2008, the China AVS workgroup started developing 3D video （3DV） coding techniques. In this paper, we discuss the background, technical features, and applications of AVS 3DV coding technology. We introduce two core techniques used in AVS 3DV coding： inter-view prediction and enhanced stereo packing coding. We elaborate on these techniques, which are used in the AVS real-time 3DV encoder. An application of the AVS 3DV coding system is presented to show the great practical value of this system. Simulation results show that the advanced techniques used in AVS 3DV coding provide remarkable coding gain compared with techniques used in a simulcast scheme.

Microlens Light Field Imaging Method Based on Bionic Vision and 3-3 Dimensional Information Transforming

his paper adopts the 3-3-2 information processing method for the capture of moving objects as its premise, and proposes a basic principle of three-dimensional (3D) imaging using biological compound eye. Traditional bionic vision is limited by the available hardware. Therefore, in this paper, the new-generation technology of microlens-array light-field camera is proposed as a potential method for the extraction of depth information from a single image. A significant characteristic of light-field imaging is that it records intensity and directional information from the lights entering the camera. Herein, a refocusing method using light-field image is proposed. By calculating the focusing cost at different depths from the object, the imaging plane of the object is determined, and a depth map is constructed based on the position of the object’s imaging plane. Compared with traditional light-field depth estimation, the depth map calculated by this method can significantly improve resolution and does not depend on the number of light-field microlenses. In addition, considering that software algorithms rely on hardware structure, this study develops an imaging hardware that is only 7 cm long based on the second-generation microlens camera’s structure, further validating its important refocusing characteristics. It thereby provides a technical foundation for 3D imaging with a single camera.

Real-Time Characterization of Crystal Shape and Size Distribution Based on Moving Window and 3D Imaging in a Stirred Tank

Crystal shape distribution, i.e. the multidimensional size distribution of crystals, is of great importance to their down-stream processing such as in filtration as well as to the end-use properties including the dissolution rate and bioavailability for crystalline pharmaceuticals. Engineering crystal shape and shape distribution requires knowledge about the growth behavior of different crystal facets under varied operational conditions e.g. supersaturations. Measurement of the facet growth rates and growth kinetics of static crystals in a crystallizer without stirring has been reported previously. Here attention is given to study on real-time characterization of the 3D facet growth behavior of crystals in a stirred tank where crystals are constantly moving and rotating. The measurement technique is stereo imaging and the crystal shape reconstruction is based on a stereo imaging camera model. By reference to a case study on potash alum crystallization, it is demonstrated that the crystal size and shape distributions (CSSD) of moving and rotating potash alum crystals in the solution can be reconstructed. The moving window approach was used to correlate 3D face growth kinetics with supersaturation (in the range 0.04 - 0.12) given by an ATR FTIR probe. It revealed that {100} is the fastest growing face, leading to a rapid reduction of its area, while the {111} face has the slowest growth rate, reflected in its area continuously getting larger.

Several Strategies on 3D Modeling of Manmade Objects

Several different strategies of 3D modeling are a do pted for different kinds of manmade objects. Firstly, for those manmade objects with regular structure, if 2D information is available and elevation information can be obtained conveniently, then 3D modeling of them can be executed directly . Secondly, for those manmade objects with complicated structure comparatively a nd related stereo images pair can be acquired, in the light of topology-based 3 D model we finish 3D modeling of them by integrating automatic and semi-automat ic object extraction. Thirdly, for the most complicated objects whose geometrica l information cannot be got from stereo images pair completely, we turn to topol ogical 3D model based on CAD.

Velocity Measurement by PIV Using W-Shaped Scanning Light Sheet

This study proposes a three-dimensional (3D) particle image velocimetry (PIV) method using W- shaped light sheet and color PIV with a digital SLR camera. The uncertainty of the velocity measurement was also studied and it was acceptable. The spatial resolution of the z-direction has much room for improvement by increasing the number of cameras. When applied to the velocity distribution measurement of a thermal vertical buoyant plume, the proposed 3D PIV method is found to be very effective for studying thermal structures and well suited for measuring the airflow velocity field.

Three-dimensional motion parameters estimation from stereo image sequences based on infrared reflective markers

In this paper,an innovative 3D motion parameters estimation method from stereo image sequences based on infrared(IR) reflective markers is presented.It was assumed that two high speed CCD cameras had been calibrated previously.The method consists of the following steps:1) the coordinate of several markers and depth map for each stereo pair was determined from the sequences of stereo images by relations of markers' coordinate the correspondence between markers was established,2) the 3D motion parameters of the target was computed based upon the matched markers' coordinate,and 3) translated 3D motion parameters estimation into the problem of least square according to the movement model of the object to be measured.Without using line,curve or corner correspondence,this method can calculate the depth of these markers feature easily and quickly in contrast to traditional approaches.The two CCD cameras work on 200 f/s,and each processing cost time is about 3 ms.It was found that,by using several markers and a large number of stereo images,this method can improve the computational speed,robustness and numerical accuracy of the motion parameters in comparison with traditional methods.The virtual simulation experiment was conducted using synthesized stereo image sequences based on 6-DOF motion platform and the experimental results proved the validity of our approach and showed that the translation and rotation precision is up to 0.1 mm and 0.1°.

垂直及斜出水流场的二维及三维TR-PIV试验

本文对钝头回转体垂直及斜出水流场采用TR-(Time-Resolved)PIV技术进行测量,并对斜出水流场进行3D-StereoPIV(三维体视PIV)测量。文中介绍了测试技术及测量结果,揭示了出水过程中流动结构及其演变,展示了TR-PIV技术对具有瞬态历程特征的出水流场研究的适应性。

应用PIV对角区非定常马蹄涡结构的实验研究

利用PIV技术研究了柱体与平板层流边界层角区的非定常流动结构,流动显示和PIV测量均表明角区存在3种非定常的马蹄涡模态,即绕合模态、脱落-绕合模态以及脱落-耗散模态,一定Re数下主涡脱落后既可能表现为脱落-绕合模态,也可能表现为脱落-耗散模态.这主要取决于模型头部形状对涡轴造成的拉伸以及耗散和扩散程度.PIV测量表明,随雷诺数增加主涡下方从壁面喷发的反向二次涡逐步增大形成强度和尺度较大的"涡舌",该"涡舌"将突入整个涡系所在的边界层,最终将主涡与上游涡系隔离并使其从旋涡生成区涡系脱落,马蹄涡非定常摆动时具有较复杂的奇点形态组合和演化,反映涡轴受到了交替的拉伸和压缩作用.

零流量工况下双叶片泵内部流场三维PIV测量

采用三维PIV测试技术对一比转数为111的双叶片泵零流量工况下的内部流动进行了测量。采用基于光纤制作的外触发同步系统和等效标定方法等关键技术来保证三维PIV测试精度。在Visual C++2005平台下,根据速度三角形,编写了三维PIV速度合成程序,将测量的绝对速度与圆周速度合成得到相对速度。结果表明:隔舌对叶轮内绝对速度场影响较大;叶轮流道内3个测量平面上都存在较大范围的漩涡区,但漩涡的大小、位置有所不同;蜗壳扩散段存在低速区域,该区域的绝对速度小于0.62 m/s,且存在漩涡现象;3个测量平面上,叶轮流道内、蜗壳扩散段及隔舌附近区域的轴向速度各不相同。