多角度投影三维显示技术的研究

设计和制作了多角度投影三维显示系统,用4个网络摄像头对一个动态的物体的4个面进行拍摄,利用视频处理软件处理视频,通过单屏投影设备将视频投影到用透明膜制作的四棱锥投影装置上,显示出三维立体的动态影像.     

单摄像机全向立体视觉传感器的结构设计

传统宽视场三维测量常采用多传感器构建的测量系统实现,传感器的同步和多传感器测量坐标系的统一两大难点导致测量精度与测量速度难以兼容。为了实现更宽视场范围内目标物的实时三维测量,设计了1种由单摄像机和2个四棱锥反射镜构成的全向立体视觉传感器。2个四棱锥反射镜对称摆放,顶部相对,下四棱锥顶端安装高分辨率工业摄像机。四棱锥反射镜成像形成4对虚拟摄像机,等效于传统双目视觉传感器的1对摄像机同时采集同名特征点,从而由4对虚拟摄像机实现水平4个方向的同步测量。解决了传统双目视觉传感器体积大、视场狭小、图像采集不同步等问题,且有效保证了图像的透视投影不变性,避免了曲面镜成像产生的图像畸变,减小了后续工作难度。     

基于旋转镜法的低成本3D成像装置

利用高速旋转的平面镜将图像投射向空间的不同位置,人眼观察时由于存在视觉残留效应,就可以观察到3D投影成像.本文基于旋转平面镜法设计并制作了包含投影装置、反馈装置和配套的软件系统的低成本高分辨率和广观察范围的三维立体投影成像系统,实现了3D投影仪器的驱动和简单3D视频的制作.     

单目多视点立体图像提取及应用

设计并实现了一种基于广角相机和平面镜的单目多视点立体图像摄像系统,给出了硬件装置的设计指标和优化方法;同时,在研究了硬件系统的标定方法基础上,实现了其在三维测距方面的应用。多枚平面镜构成的对称斗型腔体被放置在广角相机前面,物体光线经过不同平面镜反射后,投影到相机图像平面的不同区域,在相机投影平面上生成物体多个影像,形成单目多视点投影图像。该类图像等价于视点不同的多幅图像,可以使用多视点立体视觉算法实现三维测量。     

简易三维立体投影装置制作

本文报道了一种便携式简易三维立体投影装置:用四个透明反射板拼接成空心梯台,视线能从任何一面穿透,通过投影口放置的视频播放设备产生图像,图像经表面镜射和反射,从而在空心梯台的空间内形成可见的三维影像。该装置制作简单,便于携带,很好地实现了手机等便携式电子设备所播放图像或视频的三维立体投影显示。     

投影式幻影成像中局域几何畸变的校正方法研究

在幻影成像系统中,投影式成像装置具有制造成本低、成像系统操作便捷的优点,但由于投影光线发散和光源处光束偏轴角的存在,投影图像照射到四棱锥斜面时会发生几何畸变,导致三维模型失真.针对该问题,提出一种投影图像局域几何畸变的校正方法.通过提取投影图片,分析并建立投影图像形状和三维模型失真程度的映射关系,利用透视变换,构建投影...     

光学仪器 观测、投影仪器

TH741.5 2006043744多视点自由立体投影系统=Multi-view auto-stereoscopicprojection system[刊,中]/毛崇德(南京大学电子科学与工程系.江苏,南京(210093)) ,王元庆∥光电工程.—2006 ,33(4) .—59-62 ,84利用双柱面光栅的成像原理,自由立体投影系统将具有视差的画面分别成像于不同的空间区域,在成像区域形成一系列立体图像窗口,构成多视点自由立体成像。所设计的自由立体投影系统中,采用了四台高分辨率投影机,通过对1 .5 m(60英寸)双柱面投影屏幕的设计,形成了主成像窗口与副成像窗口有机拼接的宽视角(±30°)立体投影系统。经过模拟分…     

反射式多路投影立体显示系统的研究

设计了一种反射式多路投影立体显示系统,并介绍了该系统的成像原理及特性。系统将12幅视差图同时投影在柱面栅上,观察者仅凭肉眼就可看到具有双眼视差和运动视差的立体图像。系统成像视域较大,可以同时供多人观看。     

梯度轴棱锥产生单个Bottle beam

首次提出一种新的梯度轴棱锥模型,这种梯度轴棱锥在传统的轴棱锥基础上,将轴棱锥顶点的锥角设计成具有一定的梯度.平面波入射到这种梯度轴棱锥,其衍射场会形成两个区域的Bessel光,并且在这两个Bessel光之间形成一个Bottle beam（局域空心光束）.由于Bottle beam具有三维封闭的空心区域和极高的强度梯度,可用作激光导管、光镊和光学扳手等,在生命科学和纳米科技中有重要应用.从几何光学角度分析了梯度轴棱锥形成单个Bottle beam的原理,由衍射及相干理论,分析和模拟了纵向剖面光强分布和横截面光强分布.研究结果对梯度轴棱锥的设计和应用具有指导意义. 关键词： 梯度轴棱锥 Bottle beam 轴棱锥 Bessel光     

浸液式组合轴棱锥产生长距离无衍射贝塞尔光束

设计了由负轴棱锥、折射率匹配液、正轴棱锥组成的浸液式组合轴棱锥.理论分析表明:浸液式组合轴棱锥系统与传统轴正棱锥等效,同时可有效提高最大无衍射传输距离;系统产生的最大无衍射距离与负轴棱锥的底角、折射率,匹配液的折射率,正轴棱锥的底角和折射率这五个量有关,极大地增加了系统设计的灵活性,拓展了光学材料的选择范围,降低了光学元件的加工难度.     

一种基于结构光条纹投影的微小物体测量系统

为了通过结构光投影的方法测量微小物体,构建了一套微小物体三维形貌测量系统,视场范围可达1.8 cm×1.6 cm。这套测量系统利用了Light Crafter 4500数字投影组件的高速投影、立体显微镜的低畸变缩放、远心镜头的大景深与低畸变成像的特性。先利用立体显微镜对Light Crafter 4500投影的相移条纹图进行低畸变缩小,再投影到待测物体表面,采用配有远心镜头的相机同步记录受到物体表面形貌调制而发生形变的条纹,利用三步相移法计算出条纹对应的截断相位图,再根据可靠路径跟踪相位展开算法求取连续的相位分布,重建被测物体的三维表面形貌。实验成功重建了以BGA芯片为代表的微小物体表面三维形貌。实验结果表明,系统测量精度达到11 μm,系统的有效深度测量范围为700 μm。     

基于三维傅里叶频谱的计算全息图

提出了一种新的三维物体计算全息图的合成方法.在三维傅里叶旋转抛物面获取频谱理论的基础上,利用圆形扫描获得少量投影,采用多个半圆提取方式获取三维物体的频谱信息并采用共轭对称延拓计算全息编码得到计算全息图.传统方法中,在每幅投影上仅提取一个圆形的频谱信息.在同等投影数量的情况下,通过半圆方式在每幅投影上提取多于一个圆形信息的方法获得频谱信息,提高了每幅投影的信息利用率和全息图再现图像的质量.数字再现的实验证明了该方法的有效性及优越性.     

Phase-only stereoscopic hologram calculation based on Gerchberg–Saxton iterative algorithm

A phase-only computer-generated holography(CGH) calculation method for stereoscopic holography is proposed in this paper.The two-dimensional(2D) perspective projection views of the three-dimensional(3D) object are generated by the computer graphics rendering techniques.Based on these views,a phase-only hologram is calculated by using the Gerchberg–Saxton(GS) iterative algorithm.Comparing with the non-iterative algorithm in the conventional stereoscopic holography,the proposed method improves the holographic image quality,especially for the phase-only hologram encoded from the complex distribution.Both simulation and optical experiment results demonstrate that our proposed method can give higher quality reconstruction comparing with the traditional method.     

X射线三维图象显示

本文介绍的X射线三维图象显示装置是根据双目视差原理,借助于电子学及光学的方法,将不可视的X射线图象转变为可视的立体图象的装置。由两个栅控X射线管构成立体X射线源,采用高灵敏度低惰性的单氧化铅摄象机作为电视摄象系统,通过对电子图象的处理,成功地获得了立体感强、射线剂量低的三维图象。本文在论述立体成象的基本原理之后,着重叙述三维图象立体深度分析法及获得三维图象的处理方法。本装置对于物理、生物医学的研究具有重要的应用价值。 关键词：     

Free-space fluorescence molecular tomography utilizing 360 degrees geometry projections

Fluorescence tomography of diffuse media can yield optimal three-dimensional imaging when multiple projections over 360 degrees geometries are captured, compared with limited projection angle systems such as implementations in the slab geometry. We demonstrate how it is possible to perform noncontact, 360 degrees projection fluorescence tomography of mice using CCD-camera-based detection in free space, i.e., in the absence of matching fluids. This approach achieves high spatial sampling of photons propagating through tissue and yields a superior information content data set compared with fiber-based 360 degrees implementations. Reconstruction feasibility using 36 projections in 10 degrees steps is demonstrated in mice.     

Mojette变换层析技术中的投影角度布局方法

Mojette变换是一种最小冗余采样的离散Radon变换,能够用较少角度的投影数据进行精确的计算层析(computed tomography,CT)重建,为少量投影角度CT技术的实现提供了一种新思路.投影角度的空间布局决定了层析重建最少所需投影的数量.为了获得Mojette变换层析技术中的最优投影空间角度布局方案,本文对三维Mojette变换数学模型及其精确重建条件进行了研究.以此为基础,在考虑实际探测器像素数目受限的条件下,提出了确定最优投影角度的方法.研究结果表明:所有探测器围绕被测物体在同一水平面内进行平行投影采集是最优的投影角度布局方案,此时投影模型为二维Mojette变换,所需的投影角度和探测器像素数最少,投影角度范围最小;若在实际的测量中该投影条件无法满足,则投影矢量中|pi|和|qi|的值越小越好.该研究可为实际层析系统的建立提供理论基础.     

Detection of diffusion and distribution of oxygen by fast-scan EPR imaging

The diffusion and distribution of oxygen in models of biological systems have been followed by a fast-scan 2D EPR imaging apparatus. The EPR imager is based on the use of two sets of gradient coils with computer control to select projections. Currently the time per projection (six seconds) is sufficient to follow oxygen diffusion in the model systems. Typically 18–20 projections are obtained to generate an image. Using physical rotation of x/y coils, this apparatus can be used for three-dimensional EPR imaging.     

Comparison of results of interferometric phase extraction algorithms for three-dimensional flow-field tomography

A comparison of the results of interferometric phase information retrieval and subsequent tomographic reconstruction from deformed wavefront projections by phase unwrapping is presented. In interferogram processing, conventional fringe tracking and Fourier transform methods have been utilized for comparison. With these methods by injecting carrier fringes, the projection data of any axial cross section can be extracted in all projection directions to implement three-dimensional tomographic reconstruction. The results of experiments of a simulated temperature field prove that the phase extraction based on the Fourier transform method produces tomographic reconstruction much superior to the conventional fringe tracking technique.     

Finite-Rank Multivariate-Basis Expansions of the Resolvent Operator as a Means of Solving the Multivariable Lippmann–Schwinger Equation for Two-Particle Scattering

Finite-rank expansions of the two-body resolvent operator are explored as a tool for calculating the full three-dimensional two-body T-matrix without invoking the partial-wave decomposition. The separable expansions of the full resolvent that follow from finite-rank approximations of the free resolvent are employed in the Low equation to calculate the T-matrix elements. The finite-rank expansions of the free resolvent are generated via projections onto certain finite-dimensional approximation subspaces. Types of operator approximations considered include one-sided projections (right or left projections), tensor-product (or outer) projection and inner projection. Boolean combination of projections is explored as a means of going beyond tensor-product projection. Two types of multivariate basis functions are employed to construct the finite-dimensional approximation spaces and their projectors: (i) Tensor-product bases built from univariate local piecewise polynomials, and (ii) multivariate radial functions. Various combinations of approximation schemes and expansion bases are applied to the nucleon-nucleon scattering employing a model two-nucleon potential. The inner-projection approximation to the free resolvent is found to exhibit the best convergence with respect to the basis size. Our calculations indicate that radial function bases are very promising in the context of multivariable integral equations.     

Cone-beam local reconstruction based on a Radon inversion transformation

The local reconstruction from truncated projection data is one area of interest in image reconstruction for computed tomography(CT),which creates the possibility for dose reduction.In this paper,a filtered-backprojection(FBP) algorithm based on the Radon inversion transform is presented to deal with the three-dimensional(3D) local reconstruction in the circular geometry.The algorithm achieves the data filtering in two steps.The first step is the derivative of projections,which acts locally on the data and can thus be carried out accurately even in the presence of data truncation.The second step is the nonlocal Hilbert filtering.The numerical simulations and the real data reconstructions have been conducted to validate the new reconstruction algorithm.Compared with the approximate truncation resistant algorithm for computed tomography(ATRACT),not only it has a comparable ability to restrain truncation artifacts,but also its reconstruction efficiency is improved.It is about twice as fast as that of the ATRACT.Therefore,this work provides a simple and efficient approach for the approximate reconstruction from truncated projections in the circular cone-beam CT.