【作者】 林远芳；

【导师】 刘旭；

【作者基本信息】 浙江大学 ， 光学工程， 2005， 博士

【摘要】 体显示技术将三维图像描绘在一个真实的三维空间内而非二维表面上,由此产生的体图像具有与现实世界三维物体相似的大部分特性,能够呈现所有视点信息,允许多人直接从不同方位同时观看,允许用户随意走动并且总能接收到维持图像三维外观的视觉深度暗示,能够促使对数据三维形态、空间分布和动态特性等的快速、准确感知,因而这一技术在气象分析、医学成像和空中交通控制等领域中具有广阔的应用前景。本论文对基于二维LED屏旋转的体显示技术进行了系统的研究,内容涵盖其理论设计、建模仿真、系统实现、系统优化、实验论证和特性分析等各个方面,取得了良好的阶段性进展,部分成果对基于其它二维有源屏旋转的体显示技术直接适用。建立了LED体显示仿真模型和软件仿真平台。分析了LED寻址模式、体素属性和LED屏特性对三维再现质量及系统整体性能的影响,为LED体显示系统的成功建立和后续性能评价奠定了重要的理论基础。研究结果表明,利用当前小尺寸LED器件的高速电光响应特性,配合高速的旋转扫描和矩阵寻址技术,并采用具有致密LED阵列的薄的平面显示屏,能显著减小因LED时序寻址和屏幕旋转而导致的体素位置偏差,得到具有良好的体素属性、能如实表述原始图像三维特性的体图像。在上述仿真基础上构建了LED体显示实验系统。完成了从体三维数据生成、透视模拟显示、图像数据传输、信号寻址控制到图像真实再现的整套流程。系统能显示包含839万体素的全方位可视图像,能对LED进行256级亮度调制以显示体三维灰度图像。既验证了利用旋转的二维LED屏进行体显示的可行性,又为以后显示体三维彩色图像奠定了基础,同时为LED体显示特性的进一步研究提供了有效的实验平台。系统具有整体结构简单、数据处理量适中、体图像分辨率能模块化扩展等优点。论文首次从三维空间的角度,系统地研究、分析了体显示各种特性与显示系统结构及发光器件光电性能之间的关系。论述了因LED屏配光曲线不理想引起的体素亮度差异,观察了因LED屏转速变化导致的体图像被压缩现象以及因LED屏偏轴旋转引起的体图像“近小远大”畸变。研究了影响图像点再现率和体素增长率的因素,分析了图像点和体素之间位置映射偏差的统计规律性,据此筛选出合适的系统参数值。针对体素位置和密度分布不均匀问题,提出了一种以加载在图像空间内的具有均匀点距的三维阵列为基准,按照设定的基准点相邻间距和位置偏差容许值来取舍体素以便得到均匀布局的方法,为真实空间三维显示技术的研究奠定一定的基础。实验表明,这些模型分析与系统研究,对消除因重复映射和体素位置重叠导致的图像局部过亮现象,减小随定位方式变化而变化的图像再现差异,以及克服三维显示中特有的显示空间误差等都具有很好的指导作用。更多还原

【Abstract】 Volumetric display technique depicts three-dimensional (3D) images within an actual 3D space rather than upon a two-dimensional (2D) surface. The volumetric images created consequently have most characteristics similar to real-world 3D objects, providing all perspectives at once and allowing a group of viewers to directly perceive from different orientations simultaneously without the need of wearing any visual aids. Viewers can walk at will yet still receive visual depth cues to maintain the 3D appearance of images. Volumetric display technology can result in fast and accurate perception of the 3D form, spatial distribution and dynamic properties of image data, hence it has the potential to be widely used in such applications as meteorology analysis, medical imaging and air traffic control, etc.In this paper, a volumetric display technique based on the rotation of a 2D LED panel is systematically studied, concerning the theoretical design, modeling simulation, system realization, system optimization, experimental discussion and characteristics analysis, etc. Considerable staggered progress has been made. Part of this research is applicable to the volumetric display technique based on the rotation of other 2D active panels.A simulated model and a software platform of LED volumetric display system are set up in the computer. The influence of the addressing mode of LED, the attributes of voxels and the characteristics of LED panel on the reconstructed 3D image quality and the overall system performance are analyzed. These analyses provide an important theoretical basis for the successful establishment of a volumetric display system and its performance evaluation in succession. The research shows that in the case of using small LED devices of high-speed electrooptic response characteristic, adopting techniques of quick scanning and matrix addressing of a rotating thin panel which comprises a compact LED array, the position error of voxel due to the sequential addressing of LEDs and the rotation of the panel can be reduced significantly, consequently a volumetric image which has good voxel attributes and is capable of faithfully depicting the 3D characteristics of the original image will be generated.LED volumetric display experimental systems are set up based on the above-mentioned simulation. The whole process of generating volumetric 3D data, emulating a perspective display, transfering image data, addressing the LEDs and reconstructing a volumetric image are presented. One of the two experimental systems is capable of displaying images that consist of about 8.39 million voxels and can be viewed from nearly any arbitrary angle. The other is able to modulate the brightness of LED into 256 levels to display volumetric 3D gray images. The implementions of these systems have not only proved the feasibility of achieving volumetric 3D display based on the rotation of a 2D LED panel, but also establish the possibility of displaying volumetric color images in the futurer. In addition, they provide effective experimental platforms upon which the characteristics of LED volumetric display may be studied. The main advantages of these two systems are as follows. The system structure is simple and compact, the requirements of data processing are moderate, and the volumetric image display resolution is scalable, etc.The relationship of volumetric display characteristics to the system structure and the optoelectrical characteristics of the light emitting device is first studied systematically from the aspect of 3D space. The brightness difference among voxels result from the undesirable distribution curve flux of the LED panel is analyzed. The image shrink due to the variations in the LED panel’s rotational speed, and the image distortion that the nearer objects seems smaller caused by an off-axis rotating LED panel are observed. In order to single out suitable values of system parameters, factors that impact on the reconstruction percent of image points and the increment percent of voxels, along with statistical rules of the position mapping error between image points and voxels are discussed. To solve the problems involved in the inhomogeneous voxel placement and density, we put forward a method based on a homogeneous quadrate 3D array. Through keeping or abandoning potential voxel positions according to the predefined space of array pixels and the position error tolerance, voxel placement can be made almost uniform. These contents have laid a considerable basis for the researches of the 3D display technology in the real space.Experimental results show that the above-mentioned model analyses and system reseaches provides good guidelines for eliminating the phenomenon of the localized image areas are excessively brighter than the other areas due to duplicate mapping and overlap of voxels, overcoming the variations in image reconstruction effects with the changes of the image orientation, and reducing the exclusive spatial display error in 3D display.更多还原