Autostereoscopic video display with motion parallax

Abstract— A multi-viewer autostereoscopic display that provides motion parallax without encumbering the observer with special equipment is described. The display is built around a single liquid-crystal panel, from which multiple images are projected to a screen where they form the 3-D image. The display can be produced economically because it uses a single display panel and conventional optics. The primary advantage of this technique is its simplicity. Computer-generated images are supplied to the liquid-crystal panel with a single video board. 3-D television can be broadcast by a single unmodified television station (NTSC, PAL, SECAM, HDTV, etc.), and recorded and replayed in 3-D with a VCR. Applications include 3-D video arcade games, avionics, engineering workstations, scientific visualization, video phones, and 3-D television.     

Motion field and optical flow: qualitative properties

It is shown that the motion field the 2-D vector field which is the perspective projection on the image plane of the 3-D velocity field of a moving scene, and the optical flow, defined as the estimate of the motion field which can be derived from the first-order variation of the image brightness pattern, are in general different, unless special conditions are satisfied. Therefore, dense optical flow is often ill-suited for computing structure from motion and for reconstructing the 3-D velocity field by algorithms which require a locally accurate estimate of the motion field. A different use of the optical flow is suggested. It is shown that the (smoothed) optical flow and the motion field can be interpreted as vector fields tangent to flows of planar dynamical systems. Stable qualitative properties of the motion field, which give useful informations about the 3-D velocity field and the 3-D structure of the scene, usually can be obtained from the optical flow. The idea is supported by results from the theory of structural stability of dynamical systems     

On image matrix based feature extraction algorithms.

Principal component analysis (PCA) and linear discriminant analysis (LDA) are two important feature extraction methods and have been widely applied in a variety of areas. A limitation of PCA and LDA is that when dealing with image data, the image matrices must be first transformed into vectors, which are usually of very high dimensionality. This causes expensive computational cost and sometimes the singularity problem. Recently two methods called two-dimensional PCA (2DPCA) and two-dimensional LDA (2DLDA) were proposed to overcome this disadvantage by working directly on 2-D image matrices without a vectorization procedure. The 2DPCA and 2DLDA significantly reduce the computational effort and the possibility of singularity in feature extraction. In this paper, we show that these matrices based 2-D algorithms are equivalent to special cases of image block based feature extraction, i.e., partition each image into several blocks and perform standard PCA or LDA on the aggregate of all image blocks. These results thus provide a better understanding of the 2-D feature extraction approaches.     

An Efficient Approach for Dynamic Calibration of Multiple Cameras

In this paper, we propose a new algorithm for dynamic calibration of multiple cameras. Based on the mapping between a horizontal plane in the 3-D space and the 2-D image plane on a panned and tilted camera, we utilize the displacement of feature points and the epipolar-plane constraint among multiple cameras to infer the changes of pan and tilt angles for each camera. This algorithm does not require a complicated correspondence of feature points. It can be applied to surveillance systems with wide-range coverage. It also allows the presence of moving objects in the captured scenes while performing dynamic calibration. The sensitivity analysis of our algorithm with respect to measurement errors and fluctuations in previous estimations is also discussed. The efficiency and feasibility of this approach has been demonstrated in some experiments over real scenery.     

3-D position sensing using a passive monocular vision system

Passive monocular 3-D position sensing is made possible by a new calibration scheme that relates depth to focus blur through a composite lens and aperture model. The calibration technique enables the recovery of absolute 3-D position coordinates from image coordinates and measured focus blur. A geometric model of the camera's position and orientation in space is used to transform the camera's imaging coordinates into world coordinates. The relationship between the world coordinate system and the screen coordinate system which includes the amount of focus blur, is developed by modeling the camera imaging arrangement. The modeling proceeds first through the perspective view from a pinhole camera located anywhere in space. The camera's lens and aperture system is investigated to find the relationship between depth and focus blur. The aspect ratio of the frame image is considered. Position accuracies comparable to those in stereo based vision systems are possible without the need for solving the difficult point of correspondence problem     

基于直方图和模糊C均值的彩色图像分割方法

提出一种基于HSV空间的直方图和模糊C均值(FCM)相结合的彩色图像分割算法.首先将彩色图像转化到HSV空间,考虑到该空间的奇异性,把图像中的像素点根据饱和度和亮度划分为奇异点和非奇异点,然后对非奇异点建立3D HSV颜色直方图,并用爬山算法筛选出峰值进行像素点FCM聚类,对奇异点则建立1D灰度直方图,筛选出峰值进行直方图FCM聚类,最后合并两种分割结果.实验结果表明,该方法对彩色图像能够有效地提取目标物体,具有一定鲁棒性.     

Time‐multiplexed color image generation by viewing‐zone scanning holographic display employing MEMS‐SLM

The viewing‐zone scanning holographic display, which can enlarge both screen size and viewing zone, is modified to enable color image generation by using the time‐multiplexing technique; R, G, and B lasers sequentially illuminate a single microelectromechanical systems spatial light modulator with a high frame rate. The viewing‐zone scanning system enlarges screen size by using a magnifying imaging system and generates a large number of reduced viewing zones that are aligned in the horizontal direction by a horizontal scanner to enlarge the viewing zone. The interval of the reduced viewing zones is set to be one‐third of the width of the reduced viewing zones or less so that three sets of reduced viewing zones are generated corresponding to the three colors. Color image generation was demonstrated for a screen size of 2.0 in. and a viewing zone angle of 40.0°.     

Generating Dynamic Projection Images for Scene Representation and Understanding

This paper explores an interesting image projection produced by scanning dynamic scenes with a slit camera. Based on the concept of Anorthoscopic Perception, we investigate how a two-dimensionalDynamic Projection Imageof three-dimensional scenes is generated from consecutive 1-D snapshots taken through a slit, when the relative motion is homogeneous between the viewer and scenes. By moving the camera in the 3-D environment or rotating an object, we can obtain various dynamic projection images. These dynamic projection images contain major spatial and temporal information about 3-D scenes in a small amount of data. Consequently, the projection is suited for the memorization, registration, and indexing of image sequences. The generated images also directly show some of the motion properties in dynamic scenes. If a relative motion between the camera and a subject is planned properly, the dynamic projection image can even provide a texture image of the subject along with some expected photometry characteristics. Therefore, the dynamic projection can facilitate dynamic object recognition, 3-D structure acquisition, and image compression, all for a stable motion between the objects and camera. We outline various applications in vision, robotics, and multimedia and summarize the motion types and the camera setting for generating such dynamic projection images.     

The dynamics of a forced sphere-plate mechanical system

We study the dynamics and explore the controllability of a family of sphere-plate mechanical systems. These are nonholonomic systems with a five-dimensional (5-D) configuration space and three independent velocities. They consist of a sphere rolling in contact with two horizontal plates. Kinematic models of sphere-plate systems have played an important role in the control systems literature addressing the kinematics of rolling bodies, as well as in discussions of nonholonomic systems. However, kinematic analysis falls short of allowing one to understand the dynamic behavior of such systems. We formulate and study a dynamic model for a class of sphere-plate systems in order to answer the question: -is it possible to impart a net angular momentum to a sphere which rolls without slipping between two plates, given that the position of the top plate is subject to exogenous forces?”     

Surmised state of accommodation to stereoscopic three-dimensional images with binocular disparity

Three-dimensional image (3-D image) was experimentally generated by the binocular disparity principle, and psychological tests were performed in relation to the state of accommodation. An image of a square formed by the time-sharing system using liquid crystal (LC) shutter glasses was displayed before the CRT screen (forward image) by the crossed visual-line method and behind the monitor screen (backward image) by the non-crossed visual-line method. The subjects were requested to subjectively compare each image with the original image on the CRT screen in relation to the size. The forward image displayed by the crossed visual lines looked smaller than the original image, while the backward image displayed by the non-crossed visual lines looked larger. In consideration of the developmental mechanism of micropsia occurring in patients with accommodative palsy or paresis of accommodation and macropsia occurring in patients with accommodative spasm, it was surmised that, in the generation of 3-D image due to binocular disparity, accommodation works so that the original image position is maintained.     

Image mining by content

Image mining presents special characteristics due to the richness of the data that an image can show. Effective evaluation of the results of image mining by content requires that the user point of view (of likeness) is used on the performance parameters. Comparison among different mining by similarity systems is particularly challenging owing to the great variety of methods implemented to represent resemblance and the dependence that the results present of the used image set. Other obstacle is the lag of parameters for comparing experimental performance. In this paper we propose an evaluation framework for comparing the influence of the distance function on image mining by colour. Experiments with colour similarity mining by quantisation on colour space and measures of likeness between a sample and the image results have been carried out to illustrate the proposed scheme. Important aspects of this type of mining are also described.     

四旋翼吊挂运输系统动态反馈线性化轨迹控制

三维空间下的四旋翼吊挂运输系统是一种欠驱动、强耦合、多变量的非线性系统. 根据系统的动力学特点, 将系统分解为双质点系绳连接子系统和四旋翼姿态控制子系统. 选择与系统自由度维数相同的广义坐标并基于虚位移原理计算对应的广义力, 从而建立系统的拉格朗日动力学方程. 利用微分平滑特性证明了运输系统存在平凡零动态, 因此可通过动态反馈转化为线性和能控系统. 经过2次动态扩展和变量代换, 原系统扩展为总相对阶等于系统状态维度的线性能控系统. 基于赫尔维茨稳定性判据, 设计了跟踪误差指数收敛的动态反馈控制律. 该方法可作为一类非线性系统控制器设计的标准方法. 最后以三维空间的螺旋曲线及水平面内频率变化的圆周曲线为参考轨迹进行仿真, 仿真结果验证了控制系统的有效性.     

基于单幅全向图像的空间水平直线定位新方法

研究了在没有先验知识的前提下,基于单幅全向图像定位空间水平直线的问题.在已有算法的基础上,分析和推导了空间水平直线在全向成像系统中的成像特点,指出基于直线在全向图中的两个像点即可重建该水平直线,并相应地提出了一种基于"主像点/非主像点"的空间水平直线定位算法.试验表明,在不同的像点提取精度下,对于不同空间水平直线,本方法均能取得较好结果.     

基于3维提升可分离小波变换的图像水印方案

鲁棒水印技术通常被用于版权保护和所有权声明等目的。许多提出的水印方案通常把水印嵌入在变换域内,如2维的DFT域、DCT域和DWT域以及3维的DCT域、WT域。前3个域主要被用于2维的图像载体,而后2个域主要被用于3维的视频载体和3维的图像载体。在本文中,一种基于3维提升可分离小波(3-D SWT)的灰度图像水印方案被提出。首先,通过之字扫描把灰度图像分解为3维的图像序列,然后使用3-D SWT变换这些图像序列。同时通过相对熵理论证明了3-D SWT变换系数符合广义高斯分布。为了平衡鲁棒性和不可感知性,新的适用于3维的人类视觉模型被重构并用于调整水印的嵌入强度。在水印的检测方面,最优检测器实现水印的盲检测。实验表明本方案对各种攻击是强鲁棒的。     

Three-dimensional measurements of terminals of line- like objects from shadow information

A new vision system has been developed to measure the 3-D positions of wire terminals. Distance information of any visible point on the wires can be obtained from the images of the wires and from their shadows on a working table projected from a point light source. A theory is presented to determine the 3-D geometry of the wires from a picture taken by a television camera with prior knowledge of the arrangement of the environment, i.e. the camera, the working table and the light source. The wires and their shadows are extracted as strips from the input image (256 X 256 X 4) by applying thresholding and thinning operators. The relation between each wire and its shadow in the input image is established by examining the coincidences of the lines passing through each end point of all the strips and the light source in the image plane. The 3-D positions of the wires can then be determined from the geometry of the environment. A vertically mounted camera and a horizontal table are used in the experiments. The position error for fine wires was less than 1% of the size of sight. The principle, procedure and calculations of the measurement are described. Experimental results and discussions are presented.     

Personal authentication using 3-D finger geometry

In this paper, a biometric authentication system based on measurements of the user's three-dimensional (3-D) hand geometry is proposed. The system relies on a novel real-time and low-cost 3-D sensor that generates a dense range image of the scene. By exploiting 3-D information we are able to limit the constraints usually posed on the environment and the placement of the hand, and this greatly contributes to the unobtrusiveness of the system. Efficient, close to real-time algorithms for hand segmentation, localization and 3-D feature measurement are described and tested on an image database simulating a variety of working conditions. The performance of the system is shown to be similar to state-of-the-art hand geometry authentication techniques but without sacrificing the convenience of the user.     

Three-Dimensional Modeling and Effects on Still Images

Designers and creative artists use computer graphics and image processing effects on stall photographs in application areas such as advertising entertainment broadcasting and the arts Most of the effects available in research arid commercial work are two-dimensional in nature, for example image processing filters [blur, edge enhancement) and creative effects (tilings, reflections) There is almost no usage of information taken from the 3-D world in which the objects appearing an the image are located. In this paper we present a novel method for creating 3-D effects on photographs or in general on any image created by rendering a 3-D world The artist interacts with the image using a set of intuitive direct manipulation interface objects These objects let the user define a 3-D model, display at, and manipulate it in a 3-D space which is correlated with that of the input image. The generated model can be an arbitrarily complex 3-D polyhedron Any texture, including texture taken from the input photograph, can be mapped into any of its faces arid used for special effects We discuss and show examples for effects such as copy and paste, motion blur, model editing and deformations lighting effects, and shadows.     

基于FPGA的二维码图像旋转系统

阐述了在图像预处理阶段将二维码图像旋转至端正的必要性。设计了一种求取QR二维码图像旋转角度的算法以及一种可将二维码图像旋转任意角度的算法。求取旋转角度算法简捷有效,能以较低的硬件代价实现。图像旋转算法利用了CORDIC算法以及双线性插值算法,采用高速流水线架构在FPGA上实现。整个设计在Altera公司的DE2平台下进行了验证。实验结果表明,这两种算法结合使用可以快速有效地将带有一定歪斜角度的二维码图像旋转端正,速度可以达到90.9 MHz,旋转后的图像细节清晰,能有效提高二维码的识别率。