A robust omnidirectional vision sensor for soccer robots

How to make robot vision work robustly under varying lighting conditions and without the constraint of the current color-coded environment are two of the most challenging issues in the RoboCup community. In this paper, we present a robust omnidirectional vision sensor to deal with these issues for the RoboCup Middle Size League soccer robots, in which two novel algorithms are applied. The first one is a camera parameters auto-adjusting algorithm based on image entropy. The relationship between image entropy and camera parameters is verified by experiments, and camera parameters are optimized by maximizing image entropy to adapt the output of the omnidirectional vision to the varying illumination. The second one is a ball recognition method based on the omnidirectional vision without color classification. The conclusion is derived that the ball on the field can be imaged to be an ellipse approximately in our omnidirectional vision, and the arbitrary FIFA ball can be recognized by detecting the ellipse imaged by the ball. The experimental results show that a robust omnidirectional vision sensor can be realized by using the two algorithms mentioned above.     

Construction of parallel and distributed static simulation system based on augmented reality

This article puts forward a kind of parallel and distributed static augmented scene system structure to improve the performance of real time augmented simulation system.Based on static registration technique,several groups of processing nodes do parallel scene pictures taking,3D registration and virtual-real merging.Process on different nodes is controlled by uniform synchronization mechanism and network transmitting.Wide field of view image can be obtained from image mosaic operation and displayed by wide view display system.Detailed system architecture,registration algorithm,method how to determine camera position and synchronization mechanism between each process node are introduced.The experiment result can validate the good performance of the designed system.     

Design and implementation of an omnidirectional vision system for robot perception

To meet the demand of surrounding detection of a humanoid robot, we developed an omnidirectional vision system for robot perception (OVROP) with 5 Degrees of Freedom (DOFs). OVROP has a modular design and mainly consists of three parts: hardware, control architecture and visual processing part (omnidirectional vision and stereovision). As OVROP is equipped with universal hardware and software interfaces it can be applied to various types of robots. Our performance evaluation proves that OVROP can accurately detect and track an object with 360° field of view (FOV). Besides, undistorted omnidirectional perception of surroundings can be achieved through calibrations of both monocular and stereo cameras. Furthermore, our preliminary experimental results show that OVROP can perceive a desired object within 160 ms in most cases. As a result, OVROP can provide detailed information on surrounding environment for full-scope and real-time robot perception.     

Dual camera intelligent sensor for high definition 360 degrees surveillance

A novel integrated multi-camera video-sensor (panoramic scene analysis PSA) system is proposed for surveillance applications. In the proposed set-up, an omnidirectional imaging device is used in conjunction with a pan tilt zoom (PTZ) camera leading to an innovative kind of sensor that is able to automatically track at a higher zoom level any moving object within the guarded area. In particular, the catadioptric sensor is calibrated and used in order to track every single moving object within its 360 degree field of view. Omnidirectional image portions are eventually rectified and pan, tilt and zoom parameters of the moving camera are automatically adjusted by the system in order to track detected objects. In addition a co-operative strategy was developed for the selection of the object to be tracked by the PTZ sensor in the case of multiple targets.     

Virtual portraits from rotating selfies

Selfies are a popular form of photography. However, due to physical constraints, the compositions of selfies are limited. We present algorithms for creating virtual portraits with interesting compositions from a set of selfies. The selfies are taken at the same location while the user spins around. The scene is analyzed using multiple selfies to determine the locations of the camera, subject, and background. Then, a view from a virtual camera is synthesized. We present two use cases. After rearranging the distances between the camera, subject, and background, we render a virtual view from a camera with a longer focal length. Following that, changes in perspective and lens characteristics caused by new compositions and focal lengths are simulated. Second, a virtual panoramic view with a larger field of view is rendered, with the user's image placed in a preferred location. In our experiments, virtual portraits with a wide range of focal lengths were obtained using a device equipped with a lens that has only one focal length. The rendered portraits included compositions that would be photographed with actual lenses. Our proposed algorithms can provide new use cases in which selfie compositions are not limited by a camera's focal length or distance from the camera.     

弹道相机面阵CCD焦平面的光学拼接

随着科学技术的发展,弹道相机也向着高分辨率、大视场方向发展.由于现有CCD不能满足大视场的要求,因此需要多个CCD进行拼接.本文研究了面阵CCD光学拼接技术,阐述了弹道相机光学拼接的原理和焦平面结构,对拼接误差进行了分析,并针对弹道相机采用两片1 K×2 K面阵CCD进行了拼接实验.实验结果表明,该方法的搭接误差＜2μ...     

A semiparametric model for accurate camera response function modeling and exposure estimation from comparametric data.

A fundamentally new approach that accurately estimates the camera response function from comparametric data, i.e., pixel data from two differently exposed images over a common field of view, is presented. It does so by solving for the camera response function from its associated comparametric relation. The approach offers several advantageous features, including having a complexity that is independent of the number of pixel data considered, allowing for the modeling of saturated pixels, enabling an inherently constrained optimization problem to be solved in an unconstrained manner, and the easy incorporation into an existing framework for joint image registration. This is accomplished by approximating the camera response function with a constrained piecewise linear model so that its solution, within the comparametric camera relation, can be obtained. This results in a semiparametric comparametric model, optimally determined from pixel data, which is directly parameterized in terms of the exposure parameter. Subsequently, it is shown how this semiparametric model is used for exposure estimation from captured images. Finally, we incorporate the semiparametric model within an existing and previously published framework for simultaneous and joint spatial and tonal image registration in order to illustrate the developed model's performance.     

Reconstructing dense light field from array of multifocus images for novel view synthesis.

This paper presents a novel method for synthesizing a novel view from two sets of differently focused images taken by an aperture camera array for a scene consisting of two approximately constant depths. The proposed method consists of two steps. The first step is a view interpolation to reconstruct an all-in-focus dense light field of the scene. The second step is to synthesize a novel view by a light-field rendering technique from the reconstructed dense light field. The view interpolation in the first step can be achieved simply by linear filters that are designed to shift different object regions separately, without region segmentation. The proposed method can effectively create a dense array of pin-hole cameras (i.e., all-in-focus images), so that the novel view can be synthesized with better quality.     

Smoothing of Omnidirectional Horizontal Radiation Patterns of tfd TV Panel Antenna Arrays With Progressive Current Phase Shift Feeding

This paper shows how the mechanical panel displacement technique can be used effectively in order to smooth out omnidirectional patterns of TFD TV panel antenna arroys fed by progressive phase shift currents (Fig. la).     

Mosaic-based 3D scene representation and rendering

In this paper we address the problem of fusing images from many video cameras or a moving video camera. The captured images have obvious motion parallax, but they will be aligned and integrated into a few mosaics with a large field-of-view (FOV) that preserve 3D information. We have developed a compact geometric representation that can re-organize the original perspective images into a set of parallel projections with different oblique viewing angles. In addition to providing a wide field of view, mosaics with various oblique views well represent occlusion regions that cannot be seen in a usual nadir view. Stereo mosaic pairs can be formed from mosaics with different oblique viewing angles. This representation can be used as both an advanced interface for interactive 3D video and a pre-processing step for 3D reconstruction. A ray interpolation approach for generating the parallel-projection mosaics is presented, and efficient 3D scene/object rendering based on multiple parallel-projection mosaics is discussed. Several real-world examples are provided, with applications ranging from aerial video surveillance/environmental monitoring, ground mobile robot navigation, to under-vehicle inspection.     

基于光场相机结构的自适应光学系统仿真研究

在自适应光学系统中,采用传统的哈特曼波前传感器只能在较小视场范围内对大气湍流进行有效校正,而以光场相机作为波前探测器具有视场大、一次曝光可获得多视角方向湍流信息等特点,可以替代传统多层共轭自适应光学（MCAO）系统中的多个波前探测器,达到简化系统,节约成本的效果。文中采用自主研发的光学系统仿真软件Seelight中的光场相机模块,结合光场数字重聚焦技术、模式法大气层析技术,复原了大视场完整波前,并搭建了自适应光学仿真系统,模拟与89单元变形镜配合实现在闭环工作模式下对大视场的大气湍流引起波前畸变的有效校正。     

一类特定全方位摄像头外极曲线计算

研究了由双曲面镜面与球面镜面共同组成折反射系统并结合普通透视摄像头所构成的一类特定全景视觉系统,推导了该全方位摄像头成像模型以及外极曲线的计算过程,分析了外极曲线特性,最后通过实验进行理论验证.实验结果表明,本文所提出的计算方法可快速准确地得到外极曲线,有利于全景图像立体匹配过程中对应点的搜索匹配.     

基于全变分的全向图像稀疏重构算法

折反射全向成像由于曲面镜的反射作用,导致全向图像存在严重变形,传统的梯度计算方法在全向图像中不能很好地符合折反射成像的特点.为了从压缩采样数据快速有效地重构全向图像,提出了一种结合全向图像特征的全变分模型——全向全变分,并在基于TV范数进行全向图像重构时,采用全向全变分作为目标函数,进行模型的求解.实验结果验证了本文算法的有效性和可行性,其重构结果的主客观效果明显优于传统TV模型.     

基于光场相机波前传感器的气动光学效应校正研究

受气动光学效应的影响,来自目标的光波波前会产生动态扰动,导致成像模糊化。常用的校正方法是在测得波前的前提下进行解卷积处理,达到还原图像的效果。传统的波前传感器只能有效测量中心视场,由于存在非等晕问题,导致所能还原的图像区域过小。光场相机波前传感器作为一种新型波前传感器,具有视场大、动态范围大的优点,可以同时探测模糊图像不同区域的点扩散函数,从而一次性还原整幅图像。文章利用Matlab模拟了光场相机的大视场波前探测特性,对气动光学效应引起的模糊图像进行清晰化处理,并与夏克-哈特曼传感器的模拟结果进行了比较。结果表明,光场相机波前传感器可以对气动光学效应造成的波前扰动进行有效的大视场波前探测,一次探测能够清晰化整个视场的图像,且视场范围是传统波前传感器的数倍以上。     

一种斜视画幅遥感相机异速像移计算与补偿实现

以一种斜视胶片步进画幅相机为例,介绍了一种基于该相机的像移补偿策略及具体实现过程。画幅相机由于横向视场较大,使得每幅横向各个视场目标对应物距各异,最终导致目标像相对探测器产生了异速像移。对产生异速像移实质给出了数学推导,对偏流机构存在的必要性进行了分析,提出了一种利用两轴旋转扫描镜,同时结合旋转偏流机构和曝光帘缝的像移补偿方案。最后,在已知相机俯角和视场角等信息情况下,推导出了具体的像移补偿公式。     

镜像不变的折反射全向图像与透视图像匹配

该文针对折反射全向摄像机的不同配置可能使全向图像和透视图像存在的镜像关系,而尺度不变特征变换算法并不对镜像保持不变性,提出将透视图像进行一次水平翻转,然后将原图与翻转后的图像分别与全向图像进行匹配,取效果好的匹配作为最终结果,从而实现镜像不变。针对全向图像的环形畸变,提出先将透视图像变换为扇形图像后再进行匹配。实验结果显示,将透视图像变换为扇形图像后再与全向图像进行匹配,匹配点总数增加,而错误匹配点数减少,匹配结果明显好于变换前的匹配结果。     

基于棱镜的激光周视接收系统的设计

为了实现对目标全向探测和精确定位,采用成像光学与非成像光学相结合的方法,设计了一种可用于周视探测的非对称激光回波接收光学系统。由于子午和弧矢两方向视场差异很大,需加入特殊的非对称结构来平衡两方向的视场差异,该系统采用阶梯棱镜和倒置柱面望远镜对弧矢方向大视场进行角度压缩,后经过对称聚焦子系统将光能量收集到直径为1.5mm的圆形探测器上。系统由1块阶梯棱镜、1片非球面镜、2片柱面镜和2片球面镜组成,其光圈数达到0.56。结果表明,单套接收系统完成±30°视场探测,6套接收系统组合起来可实现360°周视无盲点探测。整体系统体积小、结构简单,有良好的适用性。     

Development of a lane keeping steering control by using camera vanishing point strategy

A new computer vision strategy is developed by using the Vanishing Point from camera frames for lateral control. A vehicle kinematic model is derived based on a tricycle in order to analyze the system states in the control strategy. The roots loci of the system are analyzed to understand the influence of each state in the closed-loop. On each frame, two system states are extracted from the lane lines in the perspective view by using a vanishing point-based technique with the inverse perspective mapping. A state feedback controller is developed, and computational simulations are carried out in a Blender environment using a small car model. The validation of the proposed Vanishing Point technique is carried out by several computational simulations, which also confirm the effects of each state in the final controlled system response.

     

小视场环境下的摄像机标定

摄像机标定旨在建立三维世界坐标与二维图像坐标之间的映射关系。传统标定板为数十个整齐排列的标准圆或网格,通过提取圆心坐标或网格角点坐标进行标定。在微小物体测量系统中,摄像机视场较小,无法从传统标定板提取足够多点坐标信息。针对这一问题,提出一种基于二次曲线与直线的混合标定方法。该方法抛弃了利用点对点关系的标定方法,转而利用二次曲线方程及直线方程在两种坐标系下相对应的关系进行标定,使摄像机即使是在非常小的范围内仍然能够提取足够的信息进行标定。仿真与实验证明,相对于基于点的标定方法,混合标定方法精度高,具有更好的稳健性。另外,标定模板为一个标准的半圆,制作简单,方便应用到小视场的环境中。     

航空摇摆图像组的配准拼接算法

随着航空遥感应用的不断扩大和要求的不断提高,如何扩大航空遥感拍摄的视场成为越来越关注的问题,改进航空遥感相机的拍摄方式成为扩大拍摄视场的一种重要方法.航空摇摆相机将固定式拍摄方式改为运动式拍摄方式,将每一个拍摄点拍一幅图像改为每一个拍摄点拍三幅成像平面不同但具有部分区域重叠的图像,然后通过将这三幅图像组成的图像组拼接起来得到视场更大的图像.深入研究了航空摇摆相机的摇摆模型,提出了一种摇摆图像组的配准拼接算法.实验结果表明:该摇摆图像组配准拼接算法具有良好的配准拼接效果.