Image processing and synthesis for extended depth of field of optical microscopes

An optimal microscope is useful for observing various kinds of samples. However, precise observation of an extended region in depth is difficult, because of the narrow range of depth of focus. To overcome this problem, this paper proposes a method of obtaining a pan-focused stereoscopic image. By using image processing, in-focus areas are extracted from multiple images focused on slightly different depths, and a stereoscopic image is composed with these in-focus areas. The proposed method is applied to the observation of three-dimensional distributions of soil particles, a common problem in the field of civil engineering, and the usefulness of the proposed method is demonstrated.     

Region-based depth feature descriptor for saliency detection on light field

Multimedia Tools and Applications - This paper addresses the light field saliency detection problem via a multiple cue integration framework. By reinterpreting the usage of dark channels in...     

The logic of aliasing

Summary We present a new version of Hoare's logic that correctly handles programs with aliased variables. The central proof rules of the logic (procedure call and assignment) are proved sound and complete.An earlier version of this paper appeared in the Proceedings of the Fifth ACM Symposium on Principles of Programming Languages, 1978. This research has been partially supported by National Science Foundation grants MCS 76-14293 and MCS 76-000327     

融合边缘特征的高效光场深度信息估计算法

为解决基于光场传统EPI(epipolar plane image)结构的深度信息估计算法执行效率低和估计精度低的问题,提出一种融合边缘特征的高效光场深度信息估计算法。改进传统EPI结构为包含完整像素极线信息的IEPI(improved epipolar plane image)结构和对应包含边缘信息的边缘图;构建深度多流全卷积神经网络,学习IEPI及边缘图的特征;构建基于尺度不变误差的代价函数,结合HCI光场数据集指导网络训练,实现一个估计光场深度信息的网络。实验结果表明,所提算法相较于传统算法提升了估计精度和估计效率。     

基于深度相机的手腕识别与掌心估测算法(HHME2013-ID51)

当手和手臂都进入深度相机所设定的有效深度范围时,它们将被作为一个整体来提取,若处理时也把它们作为一个整体,这可能会影响手势交互的一些重要算法,如掌心估测,手朝向估测,手的跟踪等。本文分析了手腕的运动特征和手的轮廓特点,并利用内切矩形的几何特征,提出了手腕识别算法来分割手与手臂;为了提高掌心估测算法的性能,本文分析了锐角三角形和最大内切圆的几何特征,并结合手势交互的特点,提出了新的掌心估测算法。经实验证明,手腕识别算法能较好地分割出手与手臂,新的掌心估测算法较之原算法在性能上有显著提高。     

Depth extraction using a single moving camera: an integration of depth from motion and depth from stereo

An integrated approach to extract depth, efficiently and accurately, from a sequence of images is presented in this paper. The method combines the ability of the stereo processing to acquire highly accurate depth measurements and the efficiency of spatial and temporal gradient analysis. As a result of this integration, depth measurements of high quality are obtained at a speed approximately ten times greater than that of stereo processing. Without any a priori information of the locations of the points in the scene, the correspondence problem in stereo processing is computationally expensive. In our approach, we use spatial and temporal gradient (STG) analysis, which has been shown to provide depth with great efficiency, but limited accuracy, to guide the matching process of stereo. The camera motion used in the approach can be either lateral or axial. Extensive experiments on real scenes have shown the ability of the integrated approach to acquire depth with a mean error of less than 3%.     

Effects of camera alignment errors on stereoscopic depth estimates

We present in this paper a new analysis of relative sensitivity/importance of camera calibration/alignment parameters on the performance of stereoscopic depth reconstruction. This quantitative analysis provides formulae which relate different parameter errors to the 3-D reconstruction measurements. The results of this analysis provide specifications of acceptable tolerances in individual calibration parameters for given 3-D measurement error tolerances. This information is useful in designing practical stereoscopic vision systems.     

Real-time and robust hand tracking with a single depth camera

In this paper, we introduce a novel, real-time and robust hand tracking system, capable of tracking the articulated hand motion in full degrees of freedom (DOF) using a single depth camera. Unlike most previous systems, our system is able to initialize and recover from tracking loss automatically. This is achieved through an efficient two-stage k-nearest neighbor database searching method proposed in the paper. It is effective for searching from a pre-rendered database of small hand depth images, designed to provide good initial guesses for model based tracking. We also propose a robust objective function, and improve the Particle Swarm Optimization algorithm with a resampling based strategy in model based tracking. It provides continuous solutions in full DOF hand motion space more efficiently than previous methods. Our system runs at 40 fps on a GeForce GTX 580 GPU and experimental results show that the system outperforms the state-of-the-art model based hand tracking systems in terms of both speed and accuracy. The work result is of significance to various applications in the field of human–computer-interaction and virtual reality.     

改进的后置处理景深算法

根据作为后置处理的景深对实时性、真实性等特性的需求,提出改进的方法处理景深特效.在计算散光圈半径时,使用线性化的深度,使各处深度的精度统一,并以此作为优化遮挡关系问题的基础;由于聚焦对象和非聚焦对象存在互相影响,使用平滑的散光圈插值,并把像素颜色外推的散射操作较好的模拟成GPU可直接识别的聚集操作,降低遮挡像素间的相互影响;改进散光圈内的随机采样,提高采样像素的有效性;增加一个大型模糊和小型模糊,分别应对需要过多模糊和需要较多细节处,改进模糊图像和未模糊图像的插值函数,使其能得到更好的效果.     

基于深度相机的移动机器人自主跟随技术

为解决移动机器人在复杂环境下进行自主跟随的问题,提出一种基于深度相机的自主跟随方法。搭建一个载有深度相机的全向移动平台;通过提取图像中的方向梯度直方图来检测行人,利用社会力模型预测行人的运动状态,结合分段颜色直方图信息提出一种行人模型来识别行人;利用人工势场法进行路径规划,完成自主跟随任务。实验结果表明,应用该方法移动机器人,在有行人干扰或距离行人较近的复杂环境下能够顺利的完成跟随任务。     

Flexible depth of field photography

The range of scene depths that appear focused in an image is known as the depth of field (DOF). Conventional cameras are limited by a fundamental trade-off between depth of field and signal-to-noise ratio (SNR). For a dark scene, the aperture of the lens must be opened up to maintain SNR, which causes the DOF to reduce. Also, today's cameras have DOFs that correspond to a single slab that is perpendicular to the optical axis. In this paper, we present an imaging system that enables one to control the DOF in new and powerful ways. Our approach is to vary the position and/or orientation of the image detector during the integration time of a single photograph. Even when the detector motion is very small (tens of microns), a large range of scene depths (several meters) is captured, both in and out of focus. Our prototype camera uses a micro-actuator to translate the detector along the optical axis during image integration. Using this device, we demonstrate four applications of flexible DOF. First, we describe extended DOF where a large depth range is captured with a very wide aperture (low noise) but with nearly depth-independent defocus blur. Deconvolving a captured image with a single blur kernel gives an image with extended DOF and high SNR. Next, we show the capture of images with discontinuous DOFs. For instance, near and far objects can be imaged with sharpness, while objects in between are severely blurred. Third, we show that our camera can capture images with tilted DOFs (Scheimpflug imaging) without tilting the image detector. Finally, we demonstrate how our camera can be used to realize nonplanar DOFs. We believe flexible DOF imaging can open a new creative dimension in photography and lead to new capabilities in scientific imaging, vision, and graphics.     

改进的轻型CORBA事件服务的实现

CORBA事件服务提供了ORB之间异步、多目的通信方式.但标准的事件服务规范过于繁杂,服务质量也有待改进.根据项目应用需求,对事件规范进行了扩充,引入了对事件信道进行管理的模块,同时对标准事件服务规范中的类型事件特征进行删减.然后,基于国内惟一的开源CORBA实现--Orbas,通过代理的设计模式,实现了一个轻型的事件服务,并且在接口级和应用程序级实现对QoS的提高.结果表明,该事件服务可以作为项目的消息传递中间件的底层通信模块,完成分布式对象之间的异步、多目通信.     

双目汇聚摄像系统深度信息测量研究

针对双目平行摄像系统中的盲区问题,首先提出了双目汇聚摄像系统的数学模型。然后基于这一数学模型,采用角点检测方法和外极线约束条件分别进行对应点提取和匹配,推导出双目汇聚摄像系统的物体深度计算公式。最后通过对双目汇聚模型的计算机仿真,验证算法的有效性。     

The ubiquitous camera: an in-depth study of camera phone use

Little in-depth data exists regarding what users actually do with their camera phones. Our goal was thus to understand how people use camera phone images for social and personal purposes and affective and functional purposes. We had two main objectives. The first was to explore the range and diversity of use to help broaden our outlook on current and future camera phone use. The second was to elucidate the characteristics and context of use for different activities to learn how we might better support such activities.     

LYTRO相机光场图像深度估计算法及重建的研究

光场相机目前已广泛应用于消费领域和工业应用领域,利用光场相机对目标物进行深度重建成为了一项重要的研究课题。在实际研究过程中,Lytro相机空间信息与角度信息复用于同一传感器,导致图像分辨率较低,从而使得重建效果不甚理想。为解决这一问题,提出了一种亚像素精度的光场图像深度估计方法,在频率域对子孔径图像进行多标签下的亚像素偏移,以中心视角图像为参照,建立像素匹配代价行为;使用引导滤波抑制噪声的同时保持了图像边缘;对多标签下的匹配代价行为进行优化,得到精确的深度估计结果。对目标深度图进行表面渲染、纹理映射等重建处理,得到较为精细的重建结果。实验结果表明,该算法在对复杂度较高的物体进行重建时,解决了重建模糊等问题,有较好的表现。     

A new sense for depth of field

This paper examines a novel source of depth information: focal gradients resulting from the limited depth of field inherent in most optical systems. Previously, autofocus schemes have used depth of field to measured depth by searching for the lens setting that gives the best focus, repeating this search separately for each image point. This search is unnecessary, for there is a smooth gradient of focus as a function of depth. By measuring the amount of defocus, therefore, we can estimate depth simultaneously at all points, using only one or two images. It is proved that this source of information can be used to make reliable depth maps of useful accuracy with relatively minimal computation. Experiments with realistic imagery show that measurement of these optical gradients can provide depth information roughly comparable to stereo disparity or motion parallax, while avoiding image-to-image matching problems.     

The performance of camera translation direction estimators fromoptical flow: analysis, comparison, and theoretical limits

A noniterative method using optical flow to recover the translation direction of a moving camera has been previously proposed by Heeger-Jepson (1992). In this paper we present a detailed explanation of the bias in this algorithm and compare methods for eliminating this bias, as well as presenting a comprehensive error analysis. This analysis includes a necessary modification to the Cramer-Rao lower bound (CRLB), We propose a simple iterative modification to the algorithm which produces unbiased translation direction estimates that approach the CRLB. Numerical results are used to compare the various techniques on synthetic and real image sequences     

Comparison of light field compression methods

Multimedia Tools and Applications - In this article, we compare the impact of state-of-the-art light field compression methods. It addresses quality of (a) refocused images and (b) point clouds...     

基于FPGA的结构光深度检测系统设计

为实现结构光深度检测系统的实时检测,简化结构光系统构架,降低系统成本,设计了基于现场可编程门阵列(FPGA)的结构光深度测量系统.将结构光图像处理算法进行了适应硬件的改动,利用硬件系统的流水线技术与并行运算技术,提高了系统的处理性能,提出了采用乒乓缓存结构、Box滤波与并行像素处理计算提高处理速度,保证了算法的实时性.实验表明:该系统能够实现深度探测功能,且运行速率远远优于软件处理,满足实时性要求.