【作者】 徐斌；

【导师】 桑新柱；

【作者基本信息】 北京邮电大学 ， 电子科学与技术， 2023， 硕士

【摘要】 三维显示技术能够显示物体包括深度在内的完备的三维空间信息,在包括医疗、军事、教育等许多领域都有着强烈的应用需求,是显示技术发展的一个重要研究方向。在目前众多的三维显示技术中,光场显示由于能够实现大尺寸、高质量的动态裸眼三维显示,得以从中脱颖而出。光场显示通过在空间中构建体像素来表征物体上的发光物体,体像素发出的不同方向的光线携带着不同的空间信息,经过编码后得以还原物体原始的三维光场,实现三维显示。国内外诸多学者提出了多种方法实现光场显示,并对系统观看视角、空间分辨率、视点数等关键性能指标进行了大量研究,但往往忽略了对系统视点分布均匀性的分析。本文经过分析发现视点分布不均匀问题在多数系统中是普遍出现的,而且会导致显示图像出现透视关系错误等问题,影响所还原三维空间信息的精确性和有效性。本文主要对视点分布不均匀问题的校正方法进行研究。论文的创新点和主要研究内容如下:(1)提出了基于视点匹配像素编码的视点分布不均匀校正方法。在基于柱透镜光栅的光场显示系统中,由于透镜畸变的影响,会导致系统视点分布不均匀。且随着视场角的增大,透镜畸变越严重,因而尤其是在大视角光场显示系统中,视点分布不均匀问题也会越严重。经过分析发现,视点分布不均匀会导致所构建的视点图像与视点位置不匹配,造成显示图像出现透视关系错误的问题,影响观看者对显示场景空间深度的判断。本文提出了一种基于视点匹配像素编码的合成图像实时渲染方法,在无需修改系统硬件的情况上,实现在整个观看区域内所构建的视点图像与非均匀的视点分布相匹配。实验证明,该方法将显示图像与原始采集图像间的平均SSIM值由0.7693提升至0.8135,有效解决了显示图像透视关系错误的问题,提高了显示质量。(2)提出了基于透镜像差优化的视点分布不均匀校正方法。在采用定向背光的桌面式光场显示系统中,由于透镜像差尤其是球差的影响,定向光线经过透镜折射后在焦面上无法会聚成一个理想的点,而是成一个弥散斑的形状,使得系统视点分布不均匀,在视区中间分布较密集,边缘区域分布较稀疏。经过分析发现,视点分布不均匀除了会导致显示图像出现透视关系错误的问题外,还会引起视点图像间的串扰,降低显示清晰度。本文提出了一种通过引入非球面来对透镜进行光学优化以减小像差的方法,从根本上将视点分布均匀度由39.32%提升为98.39%,从而有效解决了显示图像透视关系错误以及视点间的串扰问题。更多还原

【Abstract】 Three-dimensional display technology can display objects with complete spatial information including depth,which has a strong application demand in many fields including medical,military and education.Among numerous three-dimensional display technologies,light field display has attracted much attention because of its ability to provide large scale and high quality dynamic three-dimensional experience.Light field display constructs voxels in space to represent luminous points on real objects.Light beams emitted from voxels in different directions carry different spatial information.Natural three-dimensional display can be achieved after encoding the beams to reconstruct original light field of objects.Various methods to realize light filed display have been proposed by scholars at home and abroad.Extensive researches on viewing angle,spatial resolution and number of viewpoints have been conducted to improve performance.However,the analysis of the uniformity of viewpoint distribution has often been ignored.It is found that the problem of uneven distribution of viewpoints is common in most light field display systems,which will lead to perspective relation errors and other problems in displayed images and affect the accuracy and effectiveness of the reconstructed spatial information.The correction method of uneven distribution of viewpoints is studied in this thesis.The main innovation points and research content of this dissertation are as follows:(1)A correction method of uneven distribution of viewpoints based on viewpoint-matching pixel encoding is proposed.In light filed display systems based on cylindrical lens arrays,the distribution of viewpoints is uneven due to lens distortion.Distortion becomes severer with the increase of viewing angle.It is found that the uneven distribution of viewpoints will lead to mismatch between the reconstructed images and the viewpoint positions,resulting in the wrong perspective relation of the displayed image and affecting the viewers’perception on spatial depth.A real-time rendering method of synthetic image based on viewpoint-matching pixel encoding is proposed.The method makes the reconstructed image match the non-uniform viewpoints without modifying the system hardware.The experiments show that this method increases the average SSIM value between the displayed image and the original image from 0.7693 to 0.8135,effectively solving the problem of incorrect perspective relation of displayed images and improving the display quality.(2)A correction method of uneven distribution of viewpoints based on optimization of lenticular aberration is proposed.In tabletop light filed system based on directional backlight,the distribution of viewpoint is nonuniform due to the lenticular aberration,especially spherical aberration.The light beams emitted from the backlight source cannot converge to an ideal point but create a shape of dispersion spot on the focal plane after passing through the lens,which leads to uneven distribution of viewpoints,with dense distribution in the middle of the viewing area and sparse distribution at the edge.Analysis shows that the uneven distribution of viewpoints not only causes the incorrect perspective relation in the displayed image,but also causes the crosstalk between the adjacent viewpoints and reduces the display clarity.A method of optical optimization of lenticular lens array by introducing a aspheric surface is proposed to reduce aberration,which essentially improving the uniformity of viewpoint distribution from 39.32%to 98.39%,and effectively solving the problem of perspective relation error and crosstalk between adjacent viewpoints.更多还原