Multi-objective strategy to optimize dithering technique for high-quality three-dimensional shape measurement

Dithering optimization techniques can be divided into the phase-optimized technique and the intensity-optimized technique. The problem with the former is the poor sensitivity to various defocusing amounts, and the problem with the latter is that it cannot enhance phase quality directly nor efficiently. In this paper, we present a multi-objective optimization framework for three-dimensional(3D) measurement by utilizing binary defocusing technique. Moreover, a binary patch optimization technique is used to solve the time-consuming issue of genetic algorithm. It is demonstrated that the presented technique consistently obtains significant phase performance improvement under various defocusing amounts.

An Experimental System Development for Head Posture Estimation Based on 3-D Images Measurement

Although automobile is an indispensable vehicle to modern life, it also serves as a social problem with a big traffic accident. Among the reasons of traffic accidents, careless driving accounts for the largest part. So in order to avoid the careless driving, a system which can measure the posture of a driver and warns driver to drive carefully in the case of looking aside is necessary. Although the image measurement method is used broadly, there is a problem on which measurement accuracy is influenced by environment light, makeup of the driver, etc. in the general method based on the two-dimensional image. Therefore, in this study, we propose an image measurement method to obtain the head posture of driver. First we use three-dimensional measurement method which based on the infrared pattern projection to get 3-D information of head, and then we calculate the angle for faces. In this paper, we explain the composition method of an experiment system, and the results of head posture measurement experiment.

New Approach for 3D Shape Measurement Based on Color-Coded Fringe and Neural Network

A new 3D surface contouring and ranging system based on digital fringe projection and phase shifting technique is presented. Using the phase-shift technique, points cloud with high spatial resolution and limited accuracy can be generated. Stereo-pair images obtained from two cameras can be used to compute 3D world coordinates of a point using traditional active triangulation approach, yet the camera calibration is crucial. Neural network is a well-known approach to approximate a nonlinear system without an explicit physical model, in this work it is used to train the stereo vision application system to calculating 3D world coordinates such that the camera calibration can be bypassed. The training set for neural network consists of a variety of stereo-pair images and the corresponding 3D world coordinates. The picture elements correspondence problem is solved by using projected color-coded fringes with different orientations. Color imbalance is completely eliminated by the new color-coded method. Once the high accuracy correspondence of 2D images with 3D points is acquired, high precision 3D points cloud can be recognized by the well trained net. The obvious advantage of this approach is that high spatial resolution can be obtained by the phase-shifting technique and high accuracy 3D object point coordinates are achieved by the well trained net which is independent of the camera model works for any type of camera. Some experiments verified the performance of the method.

EFFECT OF SUBMERGED ENTRY NOZZLE (SEN) PARAMETERS AND SHAPE ON 3-D FLUID FLOW IN MOULD FOR BEAM BLANK CONTINUOUS CASTING

According to turbulent theory and characteristics of beam blank continuous casting, 3-D model to represent the flow of beam blank mould is established. The predicted results indicate that the exit obliquity of up 15°(+15°) should be adopted, which will benefit the floatation of non-metallic inclusion and purification of the molten steel. When the nozzle angle is 120°, the flow pattern is reasonable. Proper nozzle depth can be 200mm. Turbulent kinetic of meniscus can be reduced by adopting the square nozzle and suitable area of side outlet when casting speed increases. The results are consistent with those of water model experiment, so the model is exact and reasonable. The model can provide important information for design of SEN and defining of immersion depth.

ACQUIREMENT AND COMPUTER PROCESSING OF 3-D SURFACE SHAPE DATA

The laser scanning and CCD image-transmitting measurement method and principle on acquiring 3-D curved surface shape data are discussed. Computer processing technique of 3-D curved surface shape(be called“ 3 - D surface shape”for short) data is analysed. This technique in- cludes these concrete methods and principles such as data smoothing, fitting, reconstructing ,elimi- nating and so on. The example and result about computer processing of 3- D surface shape data are given .

PCA-based 3D Shape Reconstruction of Human Foot Using Multiple Viewpoint Cameras

This paper describes a multiple camera-based method to reconstruct the 3D shape of a human foot. From a foot database, an initial 3D model of the foot represented by a cloud of points is built. The shape parameters, which can characterize more than 92% of a foot, are defined by using the principal component analysis method. Then, using ＂active shape models＂, the initial 3D model is adapted to the real foot captured in multiple images by applying some constraints （edge points＇ distance and color variance）. We insist here on the experiment part where we demonstrate the efficiency of the proposed method on a plastic foot model, and also on real human feet with various shapes. We propose and compare different ways of texturing the foot which is needed for reconstruction. We present an experiment performed on the plastic foot model and on human feet and propose two different ways to improve the final 3D shapers accuracy according to the previous experiments＇ results. The first improvement proposed is the densification of the cloud of points used to represent the initial model and the foot database. The second improvement concerns the projected patterns used to texture the foot. We conclude by showing the obtained results for a human foot with the average computed shape error being only 1.06 mm.

High-accuracy 3-D deformation measurement method with an improved structured-light principle

In this paper,a high-accuracy 3-D deformation measurement(HADM)method with structured light is proposed and applied to wing deformation measurement in wind tunnel experiments.The present method employs an arbitrarily arranged fringe projector and a perpendicularly placed camera.The exact phase-height mapping using the phase differences of the projected sinusoidal fringe patterns,as well as the spatial distribution of the fringe,is accurately derived.It not only presents high feasibility but also reduces systemic uncertainties arising from deviations between the ideal model and the real-world conditions.Meanwhile,a dynamic boundary process algorithm is proposed to reduce the measurement uncertainty caused by fringe fracture near the object boundary.It is calibrated that a high accuracy with the average measurement uncertainty of 0.0237 mm is achieved,which is less than 0.01%of the side length of 25 cm of the field of view.In the wind tunnel experiments,the 3-D deformations of the elastic wing,particularly the key geometric parameters such as wing tip position,angle of attack,and dihedral angle,are well reconstructed to provide an in-depth explanation for the aerodynamic characteristics.

3-D Shape Measurement of Complex Objects by Combining Color-Coded Fringe and Neural Networks

A new approach for three dimensional (3-D) shape measurement was proposed based on colorcoded fringe and neural networks. By applying the phase-shift technique to fringe projection, point clouds were generated with high spatial resolution and limited accuracy. The picture element correspondence problem was solved by using projected color-coded fringes with different orientations. Once the high accurate corresponding points were decided, high precision dense 3-D points cloud was calculated by the well trained net. High spatial resolution can be obtained by the phase-shift technique and high accuracy 3-D object point coordinates are achieved by the well trained net, which is not dependent on the camera model and will work for any type of camera. Some experiments verify the performance of this method.

基于傅里叶变换去隔行图像的动态3维面形测量

为了解决动态面形测量中隔行扫描CCD相机记录动态物体表面变形条纹图像存在缺陷的问题,提出了傅里叶变换去隔行算法,即把隔行扫描CCD获取动态物体的错位模糊帧图像分成两个单场图像,分别对每一单场图像进行傅里叶变换去隔行处理,再利用条纹分析法重建对应时刻的3维面形。理论分析得出单场傅里叶变换去隔行图像与对应的准确满帧图像相同的结论。结果表明,该方法可以很好地恢复条纹和重建物体,且简单实用,可用于基于空间相位检测、相位测量轮廓术、傅里叶变换轮廓术等条纹分析方法的动态物体3维测量中。

全自动异形玻璃磨边机3M集成数控系统的研究

介绍具有测量-建模-加工(3M)集成的全自动异形玻璃磨边机专业数控系统的开发,并深入研究了3M集成中随动测量控制算法以及系统集成。

颜色编码正弦条纹实现孤立动态物体3维测量

采用常规条纹投影与相位分析方法,对动态物体,尤其是空间存在孤立区域、分布不连续的动态物体进行3维面形测量时,很难得到可靠的展开相位。为了解决这一问题,提出一种用颜色编码正弦条纹光栅投影测量的新方法。该方法使用二级编码的颜色信息来标记待投影的正弦条纹,从另一角度拍摄记录带有颜色信息的变形条纹图,根据编码特征进行解码获取颜色级次来确定条纹级次,并指导截断相位的展开,重建空间孤立动态物体的3维面形数据。结果表明,该算法的编码稳定、解码方式可靠,只需要拍摄1幅图就可以较好地重建空间孤立物体的3维面形。

一种管道内3维形貌检测系统

为了解决常见结构光管道内3维形貌检测系统存在光线遮挡引起测量误差和"盲区"的问题,采用了一种新改进的圆结构光垂直照明、用两个互补金属氧化物半导体摄像机同步拍摄的管道内3维形貌检测系统,建立了适合该系统的图像处理和系统标定方法,完成了检测实验。结果表明,该系统可以很好地解决"盲区"问题,减小了测量误差,系统的标准差为0.50mm,并能得到完整的管道内壁3维形貌信息。

条纹投影动态3维测量中相位高精度估计

为了提高条纹投影动态3-D形貌测量精度,采用加窗傅里叶分析辅助相移的方法来减小运动导致的相移误差。首先采用加窗傅里叶分析法估计变形条纹间的实际相移量,然后采用最小二乘法估计出变形条纹的高精度相位分布,最后由估计的相位计算得到场景3维形貌。理论分析了物体运动对相移量的影响,通过仿真研究了所提方法的相移量估计精度,并搭建了实验系统进行验证。结果表明,实验中采用所提方法的相位恢复精度达到0.1673rad,比现有方法有明显提高。该方法用来提高条纹投影动态3-D形貌测量中相位精度是有效的。

Optimized dithering technique in frequency domain for high-quality three-dimensional depth data acquisition

On the basis of the objective functions,dithering optimization techniques can be divided into the intensity-based optimization technique and the phase-based optimization technique.However,both types of techniques are spatial-domain optimization techniques,while their measurement performances are essentially determined by the harmonic components in the frequency domain.In this paper,a novel genetic optimization technique in the frequency domain is proposed for highquality fringe generation.In addition,to handle the time-consuming difficulty of genetic algorithm(GA),we first optimize a binary patch,then join the optimal binary patches together according to periodicity and symmetry so as to generate a full-size pattern.It is verified that the proposed technique can significantly enhance the measured performance and ensure the robustness to various amounts of defocusing.

Dual-frequency fringe for improving measurement accuracy of three-dimensional shape measurement

A new phase unwrapping method based on dual-frequency fringe is proposed to improve both high accuracy and large measurement range of three-dimensional shape measurement by synthesizing the projected dual-frequency fringes obtaining higher and lower frequencies.The lower-frequency one is their phase difference,which can help unwrap the wrapped phase of the higher-frequency one from their phase sum.In addition,the relationship between the measuring accuracy and the frequencies of the projected fringes is studied to guide the frequency selection in actual measurement.It is found that the closer the two frequencies are,the higher the measurement accuracy will be.The computer simulation and experiment results show the viability of this method.

The Intelligent Measuring Sub-system in the Computer Integrated and Flexible Laser Processing System

Based on the computer integrated and flexible laser p rocessing system, we developed an intelligent measuring sub-system. A novel mod el has been built to compensate the deviations of the main frame-structure, and a laser tracker system is applied to calibrate the accuracy of the system. Anal yzing the characteristics of all kind surfaces of automobile outer penal moulds and dies, the surface and border to be measured and processed are classified int o four types. A 2-D adaptive measuring method based on Bzier curve and a 3 -D adaptive measuring method based on Spline curve are developed for different types of surface. During the data processing, a 3-D probe compensation method i s described in details. The control software of the sub-measuring system is des cribed. Some measuring experiments are carried out to testify the methods.

Three-dimensional finite-time cooperative guidance for multiple missiles without radial velocity measurements

In order to simultaneously attack a target with impact angle constraint in threedimensional(3-D) space, a novel distributed cooperative guidance law for multiple missiles under directed communication topologies is proposed without radial velocity measurements. First, based on missiles-target 3-D relative motion equations, the multiple missiles cooperative guidance model with impact angle constraint is constructed. Then, in Line-of-Sight(LOS) direction, based on multiagent system cooperative control theory, one guidance law with directed topologies is designed with strict proof, which can guarantee finite time consensus of multiple missiles' impact times. Next, in elevation direction and azimuth direction of LOS, based on homogeneous system stability theory and integral sliding mode control theory, two guidance laws are proposed respectively with strict proof, which can guarantee LOS angles converge to desired values and LOS angular rates converge to zero in finite time. Finally, the effectiveness of the designed cooperative guidance law is demonstrated through simulation results.

瞬变电磁三维拟合建模方法在芨岭地区地质体三维形态分析中的应用

构造变异部位是热液型铀矿定位的有利空间,解决构造变异部位复杂三维形态分析问题对热液型铀矿定位具有重要意义。为探究瞬变电磁三维拟合技术在解决构造变异部位复杂三维形态分析中的效果,文章以甘肃龙首山芨岭地区为例,从定源回线装置测量、三分量数据处理、地质体三维形态分析等角度对瞬变电磁三维建模方法进行了应用,并与前人中心回线瞬变电磁测量视电阻率结果进行了对比,结果认为:引入三分量测量提升了数据量,为地质体复杂三维形态分析提供了必要的网格数据;瞬变电磁三维拟合建模结果的横向、纵向分辨率均优于前人测量视电阻率结果。甘肃龙首山芨岭地区瞬变电磁三维拟合应用表明:该技术对解决复杂构造变异部位三维形态分析问题,尤其是局部的形态、展布、埋深等具有较好效果,可较好的应用于热液型铀矿床浅部构造变异部位探测、断裂带及褶皱形态分析工作中。

基于条纹反射的镜面测量及三维重建算法分析

本文详细介绍了依据条纹反射术测量镜面、类镜面的原理和方法,分析了经由梯度数据重建三维面形的主要算法和关键问题。通过计算机模拟和波面实际测量,对十字路径积分法、傅里叶变换积分法和区域波前重构法三种主要算法的重建精度进行了对比研究。研究表明:区域波前重构法不但对高频噪声有较强的抑制作用,同时也可以处理复杂的连通区域和非等间距分布梯度数据的复杂情况,因此更适用于基于条纹反射术的波面测量。

数字散斑相关方法用于牙冠形状的三维测量

本文介绍了数字散斑相关方法用于牙冠形状的三维测量的过程。对于一个后牙牙冠的三维形状测量，我们首先测量该牙冠的五个面：颊面、舌面、近远中面、面，然后根据各测量面座标轴的相对位置关系，将五组局部数据转换到同一座标系中实现该牙冠的三维重建，并通过计算机绘图进行三维显示。该测量方法所获取的牙冠形状的三维数据为修复体CAD／CAM的实现奠定了数据基楚。本文还就该测量方法的特点、系统精度、三维重建中的数据结合方式、系统量程、可靠性等方面进行了讨论。