三维立体显示综述

按基本工作原理是否为双目视差将三维立体显示分为两大类。基于双目视差原理的三维立体显示主要有眼镜/头盔式立体显示和光栅式自由立体显示,这类三维立体显示的技术相对成熟并有相应产品;非基于双目视差原理的三维立体显示主要有全息立体显示、集成成像立体显示和体显示等,这类三维立体显示的技术较不成熟,大多没有相应产品。对这些三维立体显示的器件结构、工作原理以及各自的特性进行了阐述。     

基于离散傅里叶变换的数字全息水印

针对打印扫描过程对硬拷贝水印图像的攻击,提出一种抗打印扫描的全息水印改进算法。改进的算法将双水印的数字全息图隐藏在载体图像的离散傅里叶变换(DFT)中频系数的幅度谱中,并在中心对称的相应块做同样的替换,通过控制图像纹理的峰值信噪比(PSNR)自适应地控制水印嵌入强度,并实现最佳的水印嵌入。改进的算法不可见性明显提高,嵌入有意义水印容量大,具有抗剪切、噪声、JPEG压缩等攻击的优势,且通过打印扫描校正,可从打印扫描图像中清晰提取水印。     

Four-image encryption scheme based on quaternion Fresnel transform,chaos and computer generated hologram

Multimedia Tools and Applications - A novel four-image encryption scheme based on the quaternion Fresnel transforms (QFST), computer generated hologram and the two-dimensional (2D)...     

基于计算全息图的内容易碎水印技术

在图像认证中,为了鉴定图像的完整性,内容易碎水印技术得到了广泛的研究和应用.结合计算全息图的内容丰富和敏感性特点,将计算全息图作为水印信息,通过傅立叶变换产生计算全息图,然后经过加密嵌入水印.在图像的认证鉴定时,通过比较提取的水印和初始水印的相关性来鉴定图像内容的完整性.同时,图像的内容被篡改时,水印信息应该提供图像被伪造的证据.实验结果表明,基于计算全息图的内容易碎水印技术可以有效地检测出图像的篡改.     

Numerical investigation of zoomable holographic projection without a zoom lens

Holographic projection is for laser displays and has the merits of being aberration free, producing high‐contrast images, having the ability of color reconstruction with one spatial light modulator, and so on. In this paper, we propose a zoomable holographic projection without using a zoom lens and verify the proposed method by using numerical simulation. Although such a system can be readily realized to use the features of holography, which is capable of recording a large image exceeding the hologram size, the required calculation is very time consuming. For acceleration, we used shifted Fresnel diffraction for setting different sampling rates on a hologram and projected image. The proposed method can project any zoom‐in and zoom‐out image between zeroth‐order and first‐order lights, and the processing time and required memory for the zoom are constant.     

A method of chromatic aberration compensation in holographic projection display based on a single spatial light modulator

In this paper, we propose a method of chromatic aberration compensation in holographic projection display based on a single spatial light modulator (SLM). By combining the hologram of the object with that of the digital lens, three color holograms with different focal lengths can be generated. Then, the SLM is divided into three parts, input three color holograms with different focal lengths to the SLM, and each occupies one‐third area of the SLM. We verify our method, and the results show its feasibility.     

Dual-view holographic AR display based on Bragg mismatched reconstruction of the holographic optical element

A method for dual-view holographic display based on Bragg mismatched reconstruction of holographic optical element (HOE) is proposed. Under the Bragg mismatched condition, the reconstructed images are guided into two separated viewing zones to realize dual-view holographic display. Meanwhile, the viewing angle of each perspective is increased to 11.2°, which is almost 2.5 times as large as the traditional holographic display system. The design process of HOE is simple only by interference of plane reference wave and converging spherical signal wave, which has high practicability. Furthermore, the HOE can mix the virtual 3D image with real-world scenes, which could implement augmented reality (AR) display. Experiments validate that the proposed system can achieve dual-view holographic AR three-dimensional (3D) display with accommodation effect.     

Color holographic display system based on utilization of effective viewing area

In this paper, a color holographic display system based on the utilization of effective viewing area (EVA) is proposed. Color reconstruction is achieved by using a single spatial light modulator (SLM). The EVA of three color reconstructed images is analyzed based on the holographic diffraction theory and the principle of geometrical optics. Then, the effective holograms of three colors are calculated based on the EVA of the system. When three color lasers are used to collimate the SLM, three color reconstructed images can be coincided in the same position with a fast speed of calculation. Moreover, the chromatic aberration can be eliminated and the experimental results verify the feasibility of the proposed system.     

Visual effects of the luminance surrounding a computer display

The luminance surrounding a computer display can potentially reduce visibility of the display (disability glare), result in sensations of discomfort (discomfort glare) and result in transient adaptation effects from fixating back and forth between the two luminance levels. The study objective was to measure the effects of surround luminance levels upon these functions in younger and older adults to determine recommended surround luminance levels. The younger age group comprised 20 subjects (mean age 27.9 years, range 23 – 39) and the older group 17 subjects (mean age 55.5 years, range 47 – 63). The central task was presented with luminance of 91 cd/M², tested surround luminance levels were 1.4, 2.4, 8.9, 25.5, 50, 91, 175, 317, and 600 cd/M². Disability glare was tested with low contrast (20%) visual acuity charts, transient adaptation was tested with a task that required regular fixation between the two luminance levels, discomfort was measured with a questionnaire after reading stories with different surround luminance levels, and preferred luminance was measured by method of adjustment. The surround luminance significantly affected transient adaptation (p < 0.0001), optimal performance occurred at 50 cd/M² and above for the young group and at 91 cd/M² and above for the older group. Neither low contrast acuity (disability glare) nor symptoms when reading were significantly affected by surround luminance. There was wide variation in preferred surround luminance; however, average preferred surround luminance was 86.9 cd/M² for the young group and 62.2 cd/M² for the older group, slightly below the central luminance of 91 cd/M². The effects of the surround luminance within the tested range are not large; however, the data show that the lowest surround luminance levels should be avoided and that surround luminance levels at or slightly below that of the central task are preferred.     

Application of optoelectronic micro-displays for holographic binary data recorder based on computer generated fourier holograms

Present article highlights the researches provided during the development of holographic memory system based on application of computational methods to encode binary data pages as amplitude computer generated Fourier holograms (CGFH). Using electro-optical micro-display and projection optics CGFH can be recorded onto photosensitive medium. The type of display that is used in data recorder determines the specificities of optical scheme architecture with its own limitations and advantages. There are three projection schemes of binary data recorder discussed in the paper. A linear scheme based on transparency-type liquid crystal spatial light modulator (LC SLM), a scheme based on reflection-type liquid crystal on silicon spatial light modulator (LCoS SLM) which uses a beamsplitting cube, and the most compact and simple scheme based on self-emitting OLED-display. The results of experimental implementation of all the three projection schemes for CGFH of binary data pages record onto the holographic carrier and consequent optical reconstruction and analysis of the encoded data are presented.     

基于对策论的团队计算机生成角色任务分配方法

针对带有时间约束的、可以动态加入到环境中的复杂任务,建立了一种基于对策论的任务分配模型,并给出了一种任务分配方法。该方法中计算机生成角色(CGA)根据自身掌握的局部信息进行行为选择,并使用虚拟行动方法确保CGA快速学习到一个严格纯策略Nash平衡。仿真实验结果表明该方法是合理的,能够有效地解决动态任务的分配问题。     

基于单投影仪与柱面反射镜的沉浸感显示系统

在分析传统沉浸感显示系统优缺点的基础上,设计并实现了一种新型的沉浸感显示系统。该系统使用柱面反射镜对单投影仪投射光线进行反射,并在弧形背投幕上成像,能够获得无缝画面,实现了广角度虚拟场景的连贯显示。通过合理设计柱面反射镜形状,实现了投影画面在水平方向上的均匀放大。通过对图像进行预变形可以基本消除因投影幕曲率而产生的投影画面形变,同时采用背投技术使参与者在虚拟场景中活动更加自如。该系统克服了传统的多投影仪或多显示器沉浸感显示系统中存在的图像拼接问题,且易于构建,经实验验证能够获得良好的沉浸感显示效果。     

基于二代小波算法的数字全息显微成像自动对焦方法

针对传统数字全息显微重建方法难以获取最佳重建距离,且依赖于传统PC平台难以便携化等问题,设计了一种嵌入式数字全息显微自动对焦系统。该系统不仅能方便的完成数字全息显微成像的自动对焦,获取最佳重建效果,而且具有便携化的特点。该系统采用同轴全息光路配合图像传感器获取全息图,利用优化后的角谱算法实现全息重建,再结合二代小波算法对重建结果进行图像质量评价,根据评价结果找到最佳重建距离,同时获取最佳重建结果,完成自动对焦。利用该系统采集一批分辨率板全息图进行自动对焦测试。实验表明,系统的重建速度为0.6s,分辨率为3.48um,自动对焦准确率达到90%以上,实验结果验证了系统的有效性。     

一种结合DWT和DFT的彩色图像盲水印方案

为了扩大数字水印的适用范围,提出了一种彩色图像盲水印算法。在嵌入过程中,将宿主图像从RGB空间转换到YIQ空间,对其进行小波分解后再进行分块DFT变换,结合一个嵌入模板矩阵和两个伪随机序列,将Arnold置乱以后的二值图像水印嵌入到宿主图像中;在提取过程中,根据嵌入模板矩阵提取出嵌入到每一图像小块的序列,分别计算该序列和两个伪随机序列的相关性,根据相关性的大小关系恢复水印信息。实验结果表明,算法具有良好的不可见性和鲁棒性。     

基于骨架模板配准的OLED显示屏斑痕缺陷检测技术

针对OLED显示屏的自动化缺陷检测问题,提出了一种新的检测方法。首先,基于显示屏的原图像,提取其骨架信息,进行分块处理后快速地与模板图像配准,通过差影法实现斑痕缺陷的初次提取。然后通过大津法确定图像的阈值,将图像分割并进行差影操作后,实现斑痕缺陷的检测;最后,通过列举的实例,验证了本方法的有效性。     

A criterion based on Fourier transform for segmentation of connected digits

Abstract. Segmentation is the most difficult problem in handwritten character recognition systems and often causes major errors in performance. To reach a balance between speed and accuracy, a filter distinguishing connected images from isolated images for multiple stage segmentation is required. The Fourier spectrum is a promising approach to this problem, although it suffers from the heavy influence of stroke width. Therefore, we introduce SFS (SFS) to eliminate the stroke-width effect. Based on the SFS, a set of features and a fine-tuned criterion are presented to classify connected/isolated images. Theoretical analysis demonstrates their soundness, while experimental results demonstrate that this criterion is better than other methods. Received February 18, 2000 / Revised June 3, 2000     

基于FPGA的VGA波形显示方法研究

介绍了基于现场可编程门阵列(FPGA)技术实现波形显示的两种方法,同时针对波形显示中出现的不稳定性提出了一种稳定显示波形的策略。首先利用高速A/D转换器将采集的波形信号进行波形稳定控制,然后存进FPGA片内的RAM中,最后以VGA方式实时地显示出来。给出了两种方法的VGA波形显示图,并对比分析了两种方法的特点。     

A method of holographic magnification based on Fresnel diffraction

In this paper, we propose a method of holographic magnification based on Fresnel diffraction. Similarity principle of Fourier transform is used in convolution algorithm in order to adjust the size of the reconstructed image. With the splicing technology based on a spatial light modulator, the reconstructed images can be magnified. By combining the similarity principle of Fourier transform with the splicing technology, the reconstructed images can be further magnified to eight times, which is verified by the experiments.     

基于STC12C5A60S2单片机的LED显示屏硬件设计

设计使用宏晶科技的8位单片机STC12C5A60S2作为中央控制器,结合NAND闪存芯片K9F4008存储汉字库的8×128点阵LED数字屏,该点阵LED数字屏具有存储信息后离线显示的功能。可应用到多种显示环境,尤其像汽车等移动工具上的脱机显示环境．