Depth-enhanced integral imaging system with convex and composite concave micro-lens arrays

A depth-enhanced integral imaging system is proposed by using a convex micro-lens array and a composite concave micro-lens array. The convex-micro-lens array is used to provide a virtual elemental image array for the composite concave micro-lens array. The composite concave micro-lens array which has two focal lengths is used to display integral images with the virtual elemental image array. Compared with the conventional integral imaging, the proposed system can form the 3D image around two image planes with viewing angle being enhanced remarkably. The principle of the enhancement of the image depth is explained in detail and the experimental results are presented.     

Viewing-angle-enhanced integral imaging by lens switching

In spite of the many advantages of integral imaging, its narrow viewing angle has been a disadvantage. We propose a method to enhance the viewing angle of integral imaging by opening and shutting each lens in the array (i.e., the elemental lenses) sequentially. We prove our idea by using a mask that has a pattern of an on-off vertical array of apertures. Moving the mask prevents the aliasing of a neighboring lens. Thus image overlap or image flipping is reduced and the viewing angle of the system is increased.     

Aberration improvement of the floating 3D display system based on Tessar array and directional diffuser screen

The floating 3D display system based on Tessar array and directional diffuser screen is proposed. The directional diffuser screen can smoothen the gap of lens array and make the 3D image’s brightness continuous. The optical structure and aberration characteristics of the floating three-dimensional (3D) display system are analyzed. The simulation and experiment are carried out, which show that the 3D image quality becomes more and more deteriorative with the further distance of the image plane and the increasing viewing angle. To suppress the aberrations, the Tessar array is proposed according to the aberration characteristics of the floating 3D display system. A 3840?×?2160 liquid crystal display panel (LCD) with the size of 23.6 inches, a directional diffuser screen and a Tessar array are used to display the final 3D images. The aberrations are reduced and the definition is improved compared with that of the display with a single-lens array. The display depth of more than 20 cm and the viewing angle of more than 45° can be achieved.     

基于视差信息的三维图像的计算机重构*

为了解决全景成像技术中观察者位于观察区域之外看到的图像会存在失真的问题,提出了一种基于视差信息的计算机重构3D视图技术.利用3D场景中的物体点经过不同微透镜在元素图像中记录的视差信息,根据光学路径分析,对重构视图中的失真部分用其它元素图像中存在的同一物体点的匹配像素进行替代,从而得到无失真的3D视图.该技术能够在更宽的观察区域内产生3D图像.     

基于视差信息的三维图像的计算机重构

为了解决全景成像技术中观察者位于观察区域之外看到的图像会存在失真的问题,提出了一种基于视差信息的计算机重构3D视图技术.利用3D场景中的物体点经过不同微透镜在元素图像中记录的视差信息,根据光学路径分析,对重构视图中的失真部分用其它元素图像中存在的同一物体点的匹配像素进行替代,从而得到无失真的3D视图.该技术能够在更宽的观察区域内产生3D图像.     

基于滤波成像的大视角数字全息技术

为提高数字全息再现像视角,提出一种基于滤波成像的数字全息技术来实现大视角的三维物体面型测量.利用离轴像面数字全息技术,通过在4F相干图像处理系统的空间频谱面处放置可移动的低通滤波器,使满足CCD分辨率的物光波与参考光波干涉形成全息图,并控制低通滤波及成像区域分别记录不同谱段的子全息图.再现时,首先对子全息图进行数字傅里叶变换,重构对应频谱段,并对频谱段进行拼接形成完整的物光频谱|而后通过数字再现获得大视角的数字全息再现像.利用该方法测量了圆柱形表面（光滑的缝纫针）的三维形貌,并取得了较好的实验结果.     

集成成像三维显示系统显示性能的研究进展

集成成像三维显示技术是利用透镜阵列获取和显示立体图像的一种三维显示技术。本文首先综述了集成成像三维显示系统的特点,考虑其系统性能主要受分辨率、景深和观看视场角的限制,对近年来集成成像三维显示系统在增大分辨率、景深和观看视场角方面的研究进展做了综合论述,比较分析了各种改进方法的优劣。最后,对我国集成成像三维显示技术的研究现状进行了总结,并简述了本研究小组在该领域取得的若干研究成果。     

二步合成平板周视彩虹全息术

提出一种将物光波前先分解记录，再合成的二步平板周视彩虹全息术。波前的分解记录与合成彩虹全息图是分别通过转动物体和干板来实现的。记录这种周视全息图，不需要大孔径和其它特殊光学元件，即可获得周视半径大的无象差立体再现象。该方法可直接用于模压全息图母板的制作。     

Improved viewing resolution of three-dimensional integral imaging by use of nonstationary micro-optics

We propose the use of synchronously moving micro-optics (lenslet arrays) for image pickup and display in three-dimensional integral imaging to overcome the upper resolution limit imposed by the Nyquist sampling theorem. With the proposed technique, we show experimentally that the viewing resolution can be improved without reducing the three-dimensional viewing aspect of the reconstructed image.     

One-dimensional integral imaging based on parallax barrier

One-dimensional integral imaging (1DII) which only has horizontal disparity is a practical solution of high resolution in the vertical direction, low-cost, easy-viewable three-dimensional (3D) display. A 1DII based on a parallax barrier is proposed in this paper. The 1DII consists of a parallax barrier and a display panel. The operation principle and parameter calculation of the 1DII are described in detail. Two prototypes of the proposed 1DII and conventional 1DII based on a lenticular lens array are developed. The proposed 1DII improves the quality of the 3D image and provides larger viewing angle than that based on a lenticular lens array, and it is simpler and has lower cost than that based on a lenticular lens array.     

360 degree realistic 3D image display and image processing from real objects

A 360-degree realistic 3D image display system based on direct light scanning method, so-called Holo-Table has been introduced in this paper. High-density directional continuous 3D motion images can be displayed easily with only one spatial light modulator. Using the holographic screen as the beam deflector, 360-degree full horizontal viewing angle was achieved. As an accompany part of the system, CMOS camera based image acquisition platform was built to feed the display engine, which can take a full 360-degree continuous imaging of the sample at the center. Customized image processing techniques such as scaling, rotation, format transformation were also developed and embedded into the system control software platform. In the end several samples were imaged to demonstrate the capability of our system.     

Geometric analysis of spatial distortion in projection-type integral imaging

In projection-type integral imaging, positional errors in elemental images and elemental lenses affect three-dimensional (3D) image quality. We analyzed the relationships between the geometric distortion in elemental images caused by a projection lens and the spatial distortion in the reconstructed 3D image. As a result, we clarified that 3D images that were reconstructed far from the lens array were largely affected, and that the reconstructed images were significantly distorted in the depth direction at the corners of the displayed images.     

基于人眼视觉的集成成像三维显示分辨率的比较

为了对不同集成成像系统三维显示应用中的视觉分辨效果进行表征, 提出了一种基于人眼视觉的集成成像三维显示分辨率的分析比较方法. 通过分析集成成像三维显示系统的分辨率与人眼在最佳显示观看距离下分辨本领的关系, 定义了相对分辨率参数, 分析了其与集成成像三维显示实际观看时视觉分辨效果的关系. 研究结果表明, 透镜阵列的大小对集成成像三维显示的视觉分辨效果有重要的影响. 针对两个系统实例的理论计算结果表明, 系统间的相对分辨率参数差异是传统分辨率差异的1.75倍, 实验结果与理论分析一致. 该研究方法对三维显示分辨率的评价有一定的指导意义.     

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。     

背投系统视角计算方法研究

介绍了一种计算背投系统视角的方法,可用来衡量背投系统性能.背投系统的视角不仅仅依赖于背投屏幕,也与光学引擎和观看环境有关.综合这三个方面的因素得到背投系统的对比度和角度的关系,根据人眼能接受的最小对比度可推算出背投系统的视角.实验数据表明,根据方法中表达式计算所得视角与实际参量吻合较好,证明该计算方法简单有效.     

基于最小可分辨对比度的CCD成像系统最佳角放大率研究

光电成像系统存在一个最佳角放大率,使人眼与成像系统达到最佳匹配状态,系统获得最佳性能.基于MRC物理意义,提出MRC信道宽度CCD成像系统综合性能评价方法,通过实际CCD成像系统的观察实验确定了评价模型的表达式,分析了各种系统参数变化对该方法的影响.结果表明,利用MRC信道宽度评价方法描述的最佳角放大率变化与实际情况一致.在最佳角放大率情况下,系统与人眼视觉得到最佳匹配.     

基于自由曲面的裸眼3D显示柱透镜光栅设计

设计了一种用于裸眼3D显示屏的低串扰新型双面柱透镜光栅板,光栅板的入射面为等间距排列的与显示器子像素数量相同的凹形自由曲面光栅结构,出射面为斜置的凸形自由曲面光栅结构.根据裸眼3D显示原理和几何光学原理推导了双面光栅板的光栅单元自由曲面设计公式和光栅参数计算公式.通过MATLAB编程计算和SolidWorks软件建模得到光栅板模型.用TracePro软件对所设计的光栅板模型进行光线追迹仿真,结果表明:参数优化后的6视点斜置柱透镜双面光栅3D显示在最佳视角的图像串扰度为0.068%,与传统6视点斜置柱透镜光栅的最佳视角图像串扰度相比降低了2个数量级,并且在观看距离2 000mm~3 000mm范围内图像串扰度基本不变.     

利用匹配区域的纹理特征改善重构三维图像的视觉质量

研究了计算机重构三维图像时分辨率低的问题,提出一种改善3D计算机全景重构图像的视觉质量的方法,该方法利用3D空间的物体部分在每个元素图像中形成的匹配区域的纹理特征,从两个相邻的元素图像中的匹配区域提取出多个像素,经过加权计算重构出相应的图像区域.该方法与传统的计算机重构方法相比,提高了图像分辨率,同时也消除了从每个元素图像中提取多个像素直接重构图像时存在的"像素块"效应,改善了重构图像的视觉质量.     

Three-dimensional free view reconstruction in axially distributed image sensing

In this Letter, we propose a three-dimensional(3D) free view reconstruction technique in axially distributed image sensing(ADS). In typical integral imaging, free view reconstructed images can be obtained by tilting all elemental images or tilting the reconstruction plane due to large lateral perspectives for 3D objects. In conventional ADS, the reconstructed images at only a front view can be generated since the sensor is moved along with its optical axis so that it has small lateral perspectives for 3D objects. However, the reconstructed 3D images at any viewing point may be obtained because the virtual viewing camera may capture these slightly different perspectives for 3D objects. Therefore, in this Letter, we employ the virtual viewing camera to visualize the 3D images at the arbitrary viewing point. To support our proposed method, we show the experimental results.     

Three-dimensional visualization of objects in scattering medium using integral imaging and spectral analysis

This paper presents a three-dimensional visualization method of 3D objects in a scattering medium. The proposed method employs integral imaging and spectral analysis to improve the visual quality of 3D images. The images observed from 3D objects in the scattering medium such as turbid water suffer from image degradation due to scattering. The main reason is that the observed image signal is very weak compared with the scattering signal. Common image enhancement techniques including histogram equalization and contrast enhancement works improperly to overcome the problem. Thus, integral imaging that enables to integrate the weak signals from multiple images was discussed to improve image quality. In this paper, we apply spectral analysis to an integral imaging system such as the computational integral imaging reconstruction. Also, we introduce a signal model with a visibility parameter to analyze the scattering signal. The proposed method based on spectral analysis efficiently estimates the original signal and it is applied to elemental images. The visibility-enhanced elemental images are then used to reconstruct 3D images using a computational integral imaging reconstruction algorithm. To evaluate the proposed method, we perform the optical experiments for 3D objects in turbid water. The experimental results indicate that the proposed method outperforms the existing methods.