双目光学透视式头盔显示器的实验研究

采用分立元件研制双目光学透视式头盔显示器,对双目透视式头盔显示中的关键问题进行实验研究.用偏振分光棱镜作为组合镜,通过理论分析,发现图像源和外界环境的亮度随偏振片方位角呈余弦变化规律,并通过调整偏振片使头盔显示器的图像与外界环境达到最佳融合状态.调查研究了头盔显示器双目重叠范围的改变对视觉效果的影响,数据结果显示,双目重叠范围为单目视场的33～50%时效果最佳.最后根据视差原理编程制作立体图像对,分别显示于头盔显示器的左右眼,实现立体显示.     

AR增强现实在包装盒设计中的应用

目的制作基于Android平台的包装盒AR增强现实的应用程序。方法使用Unity3D软件和Vuforia插件联合开发,将包装盒设计图片上传到Vuforia官网Target Manager的Database里面,从而调用Vuforia插件里的AR相机来识别该包装盒设计图片,识别后自动将由3DMAX软件制作的三维场景叠加到AR相机的镜头中,并实现与三维场景的各项人机交互功能,最后采用Unity3D软件配置好Android SDK开发环境,就能够生成基于Android平台的包装盒增强现实的App应用程序。结果 App应用程序在手机端安装后,程序将调用手机的摄像头,当镜头拍摄到包装盒时,在包装盒上将自动叠加出虚拟的三维场景,并能够与三维模型进行交互操作,程序运行正常。结论利用AR增强现实技术制作完成的包装设计,集三维影像、声音、视频、人机交互于一体,使包装盒既具有传统的功能,还具有增强产品推广、提高消费体验、升华产品认识等功能。     

增强现实技术在远程现实中的应用研究

设计了基于移动机器人的远程现实系统,辅助机器人遥操作.为提高人机交互能力,把增强现实技术应用到远程现实当中,根据增强现实中三维注册的原理,推导了双曲面全景成像中基于视觉的注册算法,实现了三维虚拟机器人在全景图像中的注册定位.为了提供更加直观的人机交互界面,采用一种快速算法把圆形全景图进行近似的柱面展开,并将"增强远程现实"应用于展开的图像界面中.实验结果表明,增强远程现实改善了场景的视觉感官效果、增加了辅助信息,提高了人机交互能力.     

RFID-assisted assembly guidance system in an augmented reality environment

RFID technology provides an invisible ‘visibility’ to the end user for tracking and monitoring any objects that have been tagged. Research on the application of RFID in assembly lines for overall production monitoring and control has been reported recently. This paper presents a novel research on implementing the RFID technology in the application of assembly guidance in an augmented reality environment. Aiming at providing just-in-time information rendering and intuitive information navigation, methodologies of applying RFID, infrared-enhanced computer vision, and inertial sensor is discussed in this paper. A prototype system is established, and two case studies are presented to validate the feasibility of the proposed system.     

使用三角网的户外增强现实注册方式的研究

增强现实的关键技术是进行三维注册,即由真实场景计算虚实结合的参数。为扩大增强现实在户外的应用,提出了在真实场景主要物体上增加表面3D网格的方法来减少虚实结合参数计算的复杂程度。该方法既不需要增强现实室内应用开发所应用的标记,也无需目前户外应用所依赖的传感仪器。以户外地形为例,通过对视线与地形网格交点的计算快速得到以往需要两幅图像联合处理才能得到的三维信息并进行快速的虚实合成。该方法为户外增强现实系统关键技术的研究提供了一个新的思路。     

基于增强现实技术有机番茄智能包装的研究及开发

目的 为了研究增强现实技术（Augmented Reality, AR）在有机番茄包装上的应用,再现比传统包装更多的信息。方法 通过总结增强现实技术在智能包装互动体验中的应用案例,结合有机番茄的展示特性,设计包含AR技术的有机番茄纸盒包装装潢图,并设计有机番茄的三维模型及贴图、渲染,利用Unity3D和Vuforia等程序组件开发手机应用软件,通过扫描不同图案再现不同的虚拟效果。结果 以纸盒为载体基于手机端应用软件开发可以实现有机番茄智能包装的3D动画、交互性、视频等多维化的展示。结论 AR技术改变了传统包装传递信息的方式,将AR技术应用与有机番茄包装相结合,可实现基于物联网智能包装的方案。     

Three-dimensional physics-based registration of pelvic system using 2D dynamic magnetic resonance imaging slices

This paper introduces a method for dynamic 3D registration of female pelvic organs using 2D dynamic magnetic-resonance images (MRIs). The aim is to provide a better knowledge and understanding of pathologies such as prolapsus or abnormal mobility of tissues. 2D dynamic MRI sequences are commonly used in nowadays clinical routines in order to evaluate the dynamic of organs, but due to the limited view, subjectivity related to human perception cannot be avoided in the diagnoses. A novel method for 2D/3D registration is proposed combining 3D finite element models with a priori knowledge of boundary conditions, in order to provide a 3D extrapolation of the dynamic of the organs observed in a single 2D MRI slice. The method is applied to the four main structures of the female pelvic floor (bladder, vagina, uterus and rectum), providing a full 3D visualisation of the organs' displacements. The methodology is evaluated with two patient-specific data sets of volunteers presenting no pelvic pathology, and a sensitivity study is performed using synthetic data. The resulting simulations provide an estimation of the dynamic 3D shape of the organs facilitating diagnosis compared with 2D sequences. Moreover, the method follows a protocol compatible with current clinical constraints presenting this way potential short term medical applications.     

基于视线跟踪的增强现实交互

为了给增强现实系统提供一种直接、自然及双向的交互手段,本文将视线跟踪技术和增强现实技术相结合,提出了基于视线跟踪的增强现实集成原型系统,该系统既能跟踪用户的视线方向,获得用户在场景的感兴趣区域,又能体现增强现实系统的特点.针对集成系统的基本要求,结合光学透视式头盔显示器的虚拟摄像机模型,详细介绍了系统的原理,光路设计和虚拟信息注册算法.实验结果表明,集成系统达到了良好的人机交互效果,为视线跟踪与增强现实技术的广泛应用奠定了良好的基础.     

采煤机虚拟现实装配仿真系统研究

针对煤矿装备虚拟装配应用问题,基于Visual Studio 2010、OSG、Cegui、VC++等软件平台和相关硬件设备,搭建了功能完整、使用方便、交互性好、沉浸感强的某型号电牵引采煤机虚拟现实装配应用系统,详细描述了系统的功能结构、技术方案与构建方法;针对构建方法中的模型制作技术,结合UG与3Ds Max的建模优势,提出先在UG中建立CAD精确模型,后利用3Ds Max对模型进行转换、修改、优化和渲染,最终生成高质量虚拟现实模型的模型处理方法,弥补了艺术类模型装配精度较低和工程CAD模型很难直接生成虚拟现实模型的不足。     

超表面全息术：从概念到实现

对实时彩色三维动态显示的追求激发了学术界和产业界巨大的研究热情。随着“元宇宙”概念的提出,对高性能三维显示设备与技术的需求越发迫切。全息术是一种理想的三维显示方案,但传统光场调控器件却存在视场角狭窄、信息容量小等问题,阻碍了全息技术的进一步发展。而超表面作为一种新型光场调控器件,有望利用其像素尺寸小和光场调控能力强的特点在全息技术领域实现新的突破。本文主要从超表面全息器件的设计流程、调制方式、动态实现、制造技术四个方面给出了超表面全息十余年的概貌,并提出该领域未来发展的方向。

     

细晶Mg-Ce中间合金的制备及其对AZ91D组织和性能的影响

为了探索细晶Mg-Ce中间合金对AZ91D的变质效果,通过铜模喷铸法制备了细晶Mg-Ce中间合金,在此基础上研究了其对AZ91D组织和性能的影响。结果表明:经过铜模喷铸获得的细晶Mg-Ce中间合金中Mg_(12)Ce相的平均尺寸由50μm下降至10μm,相比于粗晶Mg-Ce中间合金,组织显著细化;细晶Mg-Ce中间合金的变质效果好于粗晶Mg-Ce中间合金,采用细晶MgCe中间合金变质的AZ91D相较于粗晶Mg-Ce中间合金变质的AZ91D,抗拉强度提高了5.23%,延伸率提高了15.14%,维氏硬度提高了6.92%,腐蚀速率降低了44.62%。因此,铜模喷铸是提高Mg-Ce中间合金变质效果的有效手段。     

Development and use of augmented reality and 3D printing in consulting patient with complex skull base cholesteatoma

Temporal bone and skull base anatomy is complex and can pose difficulties in patient’s perception of disease and anatomy, perceived risks, and complications of surgery. We wish to demonstrate the development and use of augmented reality (AR) technology and three-dimensional (3D) printing to assist in preoperative patient consultation in the case of a complex skull base cholesteatoma. A series of 3D models were constructed from a patient’s petrous temporal bone computed tomography (CT) scans using CAD (computer-aided design) software to display the cholesteatoma affected temporal bone and related structures. Supplementary labels and titles were also created. A two-dimensional (2D) image was created as an AR recognition marker. Both 3D and 2D assets were uploaded, linked in an AR development platform called Hyperspaces which was then published to the Hyperspaces cloud server to build an AR application for free access using a predefined keyword on an iOS mobile device. Patient’s temporal bone was also fabricated through a fused deposition modelling 3D printer using polylactic acid filament for patient consultation. AR and 3D printing allow patient-specific clinical information and complexities to be made readily available to the patient and doctor at low cost, and aid in understanding complex skull base anatomy and progressive disease such as cholesteatoma. The advancement of AR and 3D printing technologies are making complex and patient-specific 3D medical data visualisation feasible and tangible on a mobile device and in hand. Thus, these technologies can be used as an invaluable patient education and counselling tool offering a powerful medium in specialties where difficult anatomical challenges are encountered.Abbreviations: ABS: acrylonitrile–butadiene–styrene; AM: additive manufacturing; AR: augmented reality; CAD: computer-aided design; CT: computed tomography; DICOM: Digital Imaging and Communication in Medicine; FBX: Filmbox; FDM: fused deposition modelling; JPEG: joint photographic experts group; MRI: magnetic resonance imaging; PLA: polylactic acid; ROI: region of interest; STL: Stereolithography     

3D Nanofabrication via Chemo‐Mechanical Transformation of Nanocrystal/Bulk Heterostructures

Planar nanocrystal/bulk heterostructures are transformed into 3D architectures by taking advantage of the different chemical and mechanical properties of nanocrystal and bulk thin films. Nanocrystal/bulk heterostructures are fabricated via bottom‐up assembly and top‐down fabrication. The nanocrystals are capped by long ligands introduced in their synthesis, and therefore their surfaces are chemically addressable, and their assemblies are mechanically “soft,” in contrast to the bulk films. Chemical modification of the nanocrystal surface, exchanging the long ligands for more compact chemistries, triggers large volume shrinkage of the nanocrystal layer and drives bending of the nanocrystal/bulk heterostructures. Exploiting the differential chemo‐mechanical properties of nanocrystal and bulk materials, the scalable fabrication of designed 3D, cell‐sized nanocrystal/bulk superstructures is demonstrated, which possess unique functions derived from nanocrystal building blocks.     

基于镜像序列的体积显示

描述了一种基于镜像序列的体积显示方法及其原理样机.该方法用基于DMD的数字光学引擎在静止的背投屏幕上生成二维图像,此图像经沿法线方向作往复运动的前表面反光镜的反射后,形成一个连续的镜像序列.当二维图像与反光镜的位置作同步刷新时,借助视觉暂留效应,该镜像序列被观察者感知为一个具有物理景深的三维图像.该三维图像由大小一致、分布均匀的体素构成并且没有因屏厚造成的暗影,因而适合三维工程设计对象的精确显示.较之直接移动投影屏幕的方式,该方法避免了实时调焦、放大率校正等光学成像问题,同时将机械扫描的行程缩小了一半.     

Residual stress of as-deposited and rolled wire+arc additive manufacturing Ti–6Al–4V components

Wire + arc additive manufacturing components contain significant residual stresses, which manifest in distortion. High-pressure rolling was applied to each layer of a linear Ti–6Al–4V wire + arc additive manufacturing component in between deposition passes. In rolled specimens, out-of-plane distortion was more than halved; a change in the deposits' geometry due to plastic deformation was observed and process repeatability was increased. The Contour method of residual stresses measurements showed that although the specimens still exhibited tensile stresses (up to 500?MPa), their magnitude was reduced by 60%, particularly at the interface between deposit and substrate. The results were validated with neutron diffraction measurements, which were in good agreement away from the baseplate.

This paper is part of a Themed Issue on Measurement, modelling and mitigation of residual stress.     

Customised design and manufacture of protective face masks combining a practitioner-friendly modelling approach and low-cost devices for digitising and additive manufacturing

This project analyses the viability of an efficient modelling approach using a semi-automatic algorithm within a Computer Aided Design (CAD) application in combination with low-cost digitising devices and low-cost Additive Manufacturing (AM) printers when designing and manufacturing patient-specific face masks. The aims of the study were to enable clinical practitioners to utilise the advantages of three-dimensional (3D) scanning, CAD and AM without having to be trained to use design/engineering software. Face features were captured using two 3D devices. The resulting meshes were compared via the Hausdorff Distance method. A semi-automatic modelling procedure was developed with ‘Rhinoceros’ and ‘Grasshopper’ to model the face mask and customise several features. With that procedure, volunteers modelled a face mask in less than 30 minutes in their first attempt. The resulting virtual mask was manufactured with two AM printers. An initial economic study indicated that the presented approach offers a feasible alternative to the current practices.     

Past,Present, and Future of Soft-Tissue Prosthetics: Advanced Polymers and Advanced Manufacturing

Millions of people worldwide experience disfigurement due to cancers, congenital defects, or trauma, leading to significant psychological, social, and economic disadvantage. Prosthetics aim to reduce their suffering by restoring aesthetics and function using synthetic materials that mimic the characteristics of native tissue. In the 1900s, natural materials used for thousands of years in prosthetics were replaced by synthetic polymers bringing about significant improvements in fabrication and greater realism and utility. These traditional methods have now been disrupted by the advanced manufacturing revolution, radically changing the materials, methods, and nature of prosthetics. In this report, traditional synthetic polymers and advanced prosthetic materials and manufacturing techniques are discussed, including a focus on prosthetic material degradation. New manufacturing approaches and future technological developments are also discussed in the context of specific tissues requiring aesthetic restoration, such as ear, nose, face, eye, breast, and hand. As advanced manufacturing moves from research into clinical practice, prosthetics can begin new age to significantly improve the quality of life for those suffering tissue loss or disfigurement.     

Fast FE–BEM algorithms for orthotropic frictional contact

This paper presents a new and efficient methodology for solving 3D frictional contact problems considering an orthotropic friction law. The contact methodology is based on a proposed augmented Lagrangian formulation for orthotropic frictional contact problems, and a new discrete contact operator, which allows to reduce the number of unknowns in a Newton‐like algorithm that accelerates the attainment of the solution. A fast Uzawa scheme is also proposed on the basis of the Steffensen's method. Both algorithms prove to be very robust and efficient to solve orthotropic frictional contact problems. The proposed formalism has the advantage of being very compact and valid for both the FEM and the BEM. Numerical results are given to demonstrate the validity of the formulation and algorithms proposed. Copyright © 2013 John Wiley & Sons, Ltd.     

基于结构特征的海量三维模型管理方法

虚拟现实和3D可视化技术的发展带来三维模型的海量增长,传统方法采用关键字匹配方式检索和管理海量模型数据,不能满足语义级别的模型检索和管理要求.提出一种基于结构特征的海量三维模型管理方法.使用该方法的思路框架,分析海量模型实例,通过聚类与分类的方法进行概念发现,构建管理特定领域的本体库,基于本体库设计并实现基于结构特征的三维模型管理系统,最后对系统进行应用和验证.结果表明该方法很好地解决了传统三维模型管理从单一维度管理模型的低效、冗余和难以重用,实现了三维模型的多维度高效检索和管理.