Light field resampling method for elemental image array generation of integral imaging

In this paper, we proposed a light field resampling method for generating elemental image array (EIA) of integral imaging. The proposed method can break through the constraints between parameters of traditional integral imaging record device and display device and allow to generate a new set of EIA suited to be displayed in an integral imaging display device with arbitrary parameters from any given recorded EIA. Three‐dimensional display results show the correctness and superiority of the proposed method.     

Elemental image array generation method by using optimized depth image‐based rendering algorithm for integral imaging display

We propose an elemental image array (EIA) generation method by using an optimized depth image‐based rendering (DIBR) algorithm. In this method, the EIA is synthesized by the reference and virtual viewpoint elemental images, and the virtual viewpoint elemental images at the given locations are generated by DIBR algorithm. We optimize the existing DIBR algorithm by adaptively repairing the warped depth images in the processing part and extend the generation dimension of the virtual viewpoint elemental images from one dimension to two dimensions. The optimized DIBR algorithm can effectively solve the problem: the low quality of virtual viewpoint elemental images caused by discontinuous depth values and disocclusion regions. We also implement the generations of virtual viewpoint elemental images and EIA in graph processing unit to reduce the time cost. Experimental results show that the proposed method can not only improve the quality of the virtual viewpoint images but also accelerate the generations of the virtual viewpoint elemental images and EIA.     

Viewing angle enhanced integral imaging display based on double‐micro‐lens array

A viewing angle enhanced integral imaging display, which consists of a double microlens array, and a display panel is proposed. The double microlens array includes a convex microlens array and a concave microlens array. The display panel is used to display original elemental image array. The convex microlens array, located near the display panel, is used to provide a virtual elemental image array for the concave microlens array. The concave microlens array, located far away from the display panel, is used to display integral images with the virtual elemental image array. Compared with the original elemental image, the pitch for each virtual elemental image is magnified by the corresponding convex microlens. As a result, the viewing angle is expanded. Simulations based on ray‐tracing are performed and the results agree well with the theory.     

Crosstalk‐free dual‐view integral imaging display

We propose a crosstalk‐free dual‐view integral imaging display. It is composed of a display panel, a barrier array, and a micro‐lens array. The central barrier is located at the vertical central axes of the display panel and the micro‐lens array to split the element image array and the viewing zone. Moreover, other barriers are located at the margins of the elemental images and corresponding micro‐lenses to eliminate the crosstalk. The lights emitting from the left and right half of the element image array are modulated by the left and right half of the micro‐lens array to reconstruct the right and left viewing zones, respectively. A prototype of the proposed dual‐view integral imaging display is developed, and good experimental results agree well with the theory.     

Resolution enhancement of integral‐imaging three‐dimensional display using directional elemental image projection

Abstract— A new approach to resolution enhancement of an integral‐imaging (II) three‐dimensional display using multi‐directional elemental images is proposed. The proposed method uses a special lens made up of nine pieces of a single Fresnel lens which are collected from different parts of the same lens. This composite lens is placed in front of the lens array such that it generates nine sets of directional elemental images to the lens array. These elemental images are overlapped on the lens array and produce nine point light sources per each elemental lens at different positions in the focal plane of the lens array. Nine sets of elemental images are projected by a high‐speed digital micromirror device and are tilted by a two‐dimensional scanning mirror system, maintaining the time‐multiplexing sequence for nine pieces of the composite lens. In this method, the concentration of the point light sources in the focal plane of the lens array is nine‐times higher, i.e., the distance between two adjacent point light sources is three times smaller than that for a conventional II display; hence, the resolution of three‐dimensional image is enhanced.     

High‐quality direct‐view display combining multiple integral 3D images

This paper proposes a method for combining multiple integral three‐dimensional (3D) images using direct‐view displays to obtain high‐quality results. A multi‐image combining optical system (MICOS) is used to enlarge and combine multiple integral 3D images without gaps. An optical design with a simple lens configuration that does not require a diffuser plate prevents the deterioration in resolution resulting from lens arrangement errors and the diffuser plate. An experiment was performed to compare a previously developed method with the proposed method, and the latter showed a significant improvement in image quality. A method for expanding the effective viewing angle of the proposed optical design was also developed, and its effectiveness was confirmed experimentally. A prototype device of the proposed optical design was constructed using a high‐density organic light‐emitting diode (OLED) panel with 8K resolution and 1058 ppi pixel density to achieve 311 (H) × 175 (V) elemental images, a viewing angle of 20.6° in both the horizontal and vertical directions, and a display size of 9.1 in. In addition, the proposed optical design enabled making device considerably thinner, ie, with a thickness of only 47 mm.     

Viewing‐angle‐enhanced integral imaging system using high‐refractive‐index medium and curved micro‐lens array

In the integral imaging (II) system using a curved micro‐lens array (MLA), the viewing angle is limited by the gap mismatch. Here, we propose a system to decrease the gap mismatch for enhancing the viewing angle. In the proposed system, a layer of high‐refractive‐index medium is assembled between the display panel and the curved MLA. The principle of the proposed II system is studied in detail. Simulations based on ray tracing are performed, and the results show that the proposed II system can effectively enhance the viewing angle.     

Integral floating‐image display using two lenses with reduced distortion and enhanced depth

Abstract— An integral floating display (IFD) with a long depth range without floating lens distortion is proposed. Two lenses were used to reduce barrel distortion of the floating lens and three‐dimensional (3‐D) image deformation from object‐dependent longitudinal and lateral magnifications in the floating‐display system, combined with an integral imaging display. The distance between the floating lenses is the sum of their focal lengths. In the proposed configuration, lateral and longitudinal magnifications are constant regardless of the distance of the integrated 3‐D images, so the distortions from the distant‐dependent magnifications of the floating lens do not occur with the proposed method. In addition, the proposed floating system expands the depth range of the integral imaging display. As a result, the display can show a correct 3‐D floating image with a large depth range. Experimental results demonstrate that the proposed method successfully displays a 3‐D image without floating lens distortions across a large depth range.     

Implementation of polarization‐multiplexed tiled projection integral imaging system

Abstract— A 40‐in. tiled projection integral imaging system has been implemented, adopting a polarization‐multiplexing technique. The system is composed of two full‐high‐definition (HD) projectors, a time‐varying polarizer, a polarization preserving screen, polarization films, a lens array, and a control unit. An elemental image set is projected using two full‐HD projectors to enhance the resolution of the system. The viewing region of the system is increased by using a polarization switching method. The polarization state of the elemental image set is changed by the time‐varying polarizer, and the elemental image set is diffused by the polarization preserving screen. The elemental image set with a preserved polarization state forms a three‐dimensional image with increased viewing angle by the integration of a lens array with polarization films. A 60‐in. tiled projection integral imaging system was also demonstrated using four full‐HD projectors.     

Double‐viewing‐zone integral imaging 3D display without crosstalk based on a tilted barrier array

We propose an integral imaging (II) three‐dimensional (3D) display using a tilted barrier array and a stagger microlens array. The tilted barrier array consists of two orthogonally polarized sheets. In the stagger microlens array, the center of the microlens has p/2 shift with the elemental image along the horizontal direction, where p is the pitch of the microlens. The proposed II 3D display produces two different viewing zones and each of them is almost equal to that of the conventional II 3D display, and it has no crosstalk. We verify the feasibility of the proposed II 3D display in the simulation results.     

Practical implementation of a depth‐feeling‐enhanced two‐plane electro‐floating display system using three‐dimensional integral images

Abstract— Although there are numerous types of floating‐image display systems which can project three‐dimensional (3‐D) images into real space through a convex lens or a concave mirror, most of them provide only one image plane in space to the observer; therefore, they lack an in‐depth feeling. In order to enhance a real 3‐D feeling of floating images, a multi‐plane floating display is required. In this paper, a novel two‐plane electro‐floating display system using 3‐D integral images is proposed. One plane for the object image is provided by an electro‐floating display system, and the other plane for the background image is provided with the 3‐D integral imaging system. Consequently, the proposed two‐plane electro‐floating display system, having a 3‐D background, can provide floated images in front of background integral images resulting in a different perspective to the observer. To show the usefulness of the proposed system, experiments were carried out and their results are presented. In addition, the prototype was practically implemented and successfully tested.     

基于多视图像的摄像机自标定方法

摄像机标定是三维重建时的必要步骤。传统的标定方法对设备要求高、操作繁琐,而自标定方法虽然简便,但精度不高,会严重影响三维重建的效果。因此,越来越需要一种操作简便并且精度高的自标定方法。采用SIFT特征点匹配算法,根据多视序列图像中对应点间的相互关系,利用光束法平差,提出了一种基于局部-全局混合优化的迭代优化方法。针对图像匹配量大的问题,提出了一种邻域内图像互匹配方法来降低时间代价。实验表明,本文提出的多摄像机自标定方法是一种有效的高精度方法,采用的邻域内图像互匹配技术能很好地降低图像匹配的时间消耗。根据多视图像的对应点间相互关系,充分利用局部-全局优化的思想,通过混合优化的方法得到相机参数,对比现有自标定算法,本文给出的方法有较高的精度和鲁棒性。     

基于Hermite插值的视频图像分辨率匹配电路设计

目前常用的图像分辨率匹配算法,存在着缩放效果模糊或硬件消耗过大等问题。综合缩放效果和电路消耗考虑,提出了一种基于三次Hermite插值算法的图像分辨率匹配电路。以基于数字差分分析算法的模块控制插值源像素的选取,以Hermite算法为内核完成插值系数的计算,相对双三次插值算法,保证了较小的硬件消耗。通过均方差、峰值信噪比、灰度梯度模值和傅里叶频谱对Hermite插值算法缩放效果与其余算法缩放效果进行定量分析,表明三次Hermite插值算法比双线性插值算法具有更好的缩放效果。同时通过电路综合结果,表明该电路相对基于双三次插值的电路,硬件消耗更小。     

基于分层多模板匹配的影像自动配准方法研究

提出一种基于分层多模板匹配的高空间分辨率影像的自动配准方法,并根据不同季相遥感影像的特点提出稳定性模板自动选取的方法和流程,详细描述了基于梯度能量的模板选取方法,以及如何筛选容易受到噪声、动态目标干扰的模板区域,如基于植被覆盖度的方法筛选可能受到植被季相变化的模板。同时,还运用了小波多尺度图像分解和自适应匹配的方法来减小模板匹配中数据计算量和搜索空间。通过模板匹配的精度和最小二乘法对匹配后的模板进行筛选,建立图像之间的影射关系,从而实现遥感影像的自动配准。     

基于群智感知的街景变化检测方法

移动群智感知数据包含的图像和时空情境信息可用于检测街景图像变化,但是群智感知数据通常是低质和不规范的。为了准确检测街景发生的变化,主要解决由拍摄视角差异引起的数据低质问题。首先,针对大视差问题采用图像配准方法初步对齐图像并提取出配准特征点;然后,基于配准特征点分布从图像中提取感兴趣区域;随后,针对差值图像的误检内容,提出基于面积和多特征点的筛选法去除误检区域;最后,结合边缘检测和超像素分割算法提取完整的变化对象。与MDFNet方法进行比较,实验结果显示：当街景发生变化时,该方法的F1-measure值为55.8%,增长6%,错误率为10.8%,降低24%;当街景无变化时,该方法的错误率为2.8%,下降28%。     

基于积分图和粒子群优化的肤色分割

为了更快地将肤色区域从图像中分割出来,在二维Ostu方法的基础上,提出了一种将积分图和粒子群优化相结合用于寻找最优分割阈值点的新方法。该方法通过对经过颜色补偿后的图片在YCbCr颜色空间中用二维高斯肤色模型计算肤色概率图,根据二维Ostu算法确定粒子群优化的目标函数,将积分图的方法用于粒子群优化中目标函数的计算,在有效地获取最佳阈值点的同时减少了计算量。实验表明,该方法能有效并且快速地分割出肤色区域。     

Measurement and analysis on the accommodation responses to real‐mode,virtual‐mode,and focused‐mode integral imaging display

Integral imaging has three display modes including real mode, virtual mode, and focused mode, and each mode has unique display characteristics. In this paper, the accommodation responses to the three‐dimensional (3‐D) targets reconstructed by each mode of the integral imaging display were measured and statistically analyzed. Through the least square method, standard deviation analysis, and t‐test analysis, we found that the accommodation responses to the 3‐D target reconstructed by the focused mode was more similar to that of the real target on the same depth position. Moreover, the closer to the central depth plane was, the steadier accommodation response 3‐D targets could provide. These statistical analysis results are helpful to the design of integral imaging display device.     

基于立体视觉的在线实时测量系统设计与实现

为了满足深空探测器实时测量天体表面形貌的需求,设计并实现了一套基于立体视觉的在线实时测量原型系统。该系统通过立体相机实时获取空间天体的立体影像,利用每次观测的一组立体影像来重建其局部表面形状;再对每次重建的局部模型进行连接,得到空间天体完整的表面形貌模型。通过仿真实验验证了该系统的可行性,数据处理的速度与精度可以满足对深空目标进行实时测量的需要。     

基于小波多尺度分解的互补全景图像融合

为了解决折反射成像内外环分辨率低且不均匀的问题,针对互补全景图像的特点,提出了一种基于小波多尺度分解的图像融合方法。首先对两幅互补的源图像分别进行小波多尺度分解,得到不同分辨率、不同方向的分量;其次,按照特定的融合策略,低频采用平均算子进行融合,高频采用逐层互换的融合策略进行融合;最后,通过小波逆变换得到融合图像。实验结果表明,该方法在互补全景图像的融合中简单有效,并且拥有较好的效果。