Horizontal parallax distortion in toed-in camera with wide-angle lens for mobile device

An effect of the toed-in camera configuration is keystone distortion, which causes vertical and horizontal parallax in the stereoscopic image. The horizontal parallax is the source of the depth plane curvature. However, if the stereoscopic image captured by the toed-in camera system with fish-eye lens is displayed on mobile device, it is uncomfortable to view because the horizontal parallax contains horizontal parallax distortion occurred by the wide field of view of the lenses. Therefore, in this paper, we propose a novel correction method of the horizontal parallax distortion, which is one of the keystone distortions, in a toed-in camera with fish-eye lenses for mobile device. We have experimented to attest the proposed method. In experiment, we used two charge coupled device cameras, whose field of view is 48.48°. In addition, the captured stereoscopic image was corrected for the barrel distortion and the horizontal parallax distortion. Therefore, the proposed method provides correcting of the horizontal parallax distortion from a toed-in camera system in order that the users can enjoy three-dimensional effects without the visual fatigue. Additionally, the proposed method is able to apply to toed-in camera consisting of any kinds of cameras.     

功率谱在高分辨率遥感相机检调焦中的应用

检调焦是高分辨力遥感相机得到高质量图像的关键技术之一。线阵CCD遥感相机在推扫过程中地面景物不断变化,而一般的图像清晰度评价函数只能在相同的图像内容下作比较来判断系统是否合焦。在介绍了遥感相机离焦原因及常用检调焦方法的基础上,用遥感图像验证了图像的功率谱对自然景物具有一定的不变性,分析了将其用于相机检调焦的可行性。实验表明,在系统合焦时,不同图像的功率谱值基本相同;而系统离焦时,功率谱值随着离焦程度的增加而逐渐减小,以此提出了以两幅不同图像功率谱的比值作为CCD遥感相机调焦的评价函数。     

Evaluating NIR-Red and NIR-Red edge external filters with digital cameras for assessing vegetation indices under different illumination

Consumer-grade digital cameras with or without external filters are recognized as a cost-effective method of vegetation monitoring. These cameras could produce time series information related to biophysical properties of vegetation. This paper evaluates the use of low-cost external filters with digital cameras for assessing vegetation indices (VIs). The system was implemented for ground-based (handheld) remote sensing in assessing biophysical properties of vegetation like plant phenology and Chlorophyll content. It also has high potential for above-canopy measurement using low-altitude remote sensing (LARS). In this study the modified cameras were used to capture near-infrared (NIR), red-edge (RE), and red (R) bands using proposed external filters. We use the low-cost NIR-R and NIR-RE external filters with modified cameras and tested the cameras performance using custom chamber under different illumination. Based on our findings, a method was proposed for enhancing the value of VI, which comprised the extracted DN of two broadbands like NIR and R. New ranges of broadband in red edge area (RE_high and RE_low) are proposed as alternative bands in estimating Chlorophyll content. In addition, evaluation and implementation for assessing VIs are detailed in this study.     

双目立体视觉测距系统误差模型的研究

针对双目立体视觉测距中产生误差的问题,分析了系统中的各个参量,并建立了双目立体视觉测距系统的误差模型。得出引起测量系统误差最大的两个参量是CCD摄像头的对准程度和测量的距离;在视场中心的距离测量精度低,边缘测量精度高,在视场中心的水平和纵向的测量精度却远高于在边缘的测量精度两个结论。基于本文建立的误差模型可以指导适用于具体应用场合的双目立体视觉测距系统的设计。     

Calibration of a wide angle stereoscopic system

Inaccuracies in the calibration of a stereoscopic system appear with errors in point correspondences between both images and inexact points localization in each image. Errors increase if the stereoscopic system is composed of wide angle lens cameras. We propose a technique where detected points in both images are corrected before estimating the fundamental matrix and the lens distortion models. Since points are corrected first, errors in point correspondences and point localization are avoided. To correct point location in both images, geometrical and epipolar constraints are imposed in a nonlinear minimization problem. Geometrical constraints define the point localization in relation to its neighbors in the same image, and eipolar constraints represent the location of one point referred to its corresponding point in the other image.     

基于MAX9259/MAX9260的CameraLink图像数据光纤传输技术

为了提高光电经纬仪上图像传输系统的性能,建立了光纤传输系统,本文针对传统Camera Link光纤传输系统方案中FPGA开发繁琐的问题,结合Camera Link接口协议和串行/解串行技术,设计了一种新的base型Camera Link的光纤传输系统,该系统采用Ser Des芯片组MAX9259/MAX9260代替编解码芯片,实现数据在Cameralink并行接口与光电转换模块串行接口之间的相互转化,并通过两种实验方案验证了系统的可行性。该方案省去传统方案中时分复用及异步FIFO缓存,降低了光纤传输系统的开发难度,并缩短了研发周期。实验结果表明:系统传输速率达到2. 5 Gb/s,具有传输稳定可靠,传输图像质量好,带宽高,抗电磁干扰能力强等特点,可满足多种像素时钟相机的需求。     

Illusion optics

The technique of “transformation optics” establishes a correspondence between coordinate transformation and material constitutive parameters. Most of the transformation optics mappings give metamaterials that have graded positive refractive indices that can steer light in curves defined by the coordinate transformation. We will focus on those “folded-geometry mappings” that give negative refractive index materials that have special wave scattering properties. One interesting example is a kind of remote illusion device that can transform the stereoscopic image of an object into the illusion of some other object of our choice. The conceptual device can create the illusion without touching or encircling the object. For any incident wave, the device transforms the scattered waves of the original object into that of the object chosen for illusion outside a virtual boundary. We will illustrate some possible applications of this type of metamaterial remote device, including “cloaking at a distance,” partial cloaking, cloaking from an embedded device, revealing a hidden object inside a container, turning the image of one object into that of another object, and seeing through a wall. The feasibility of building this remote illusion device by metamaterials will also be discussed.     

集成SIFT算法与检测模型优化的UAV影像匹配方法

低空无人机(UAV)测量凭借着低成本、高效率、高精度的数据采集模式,可快速获取高空间分辨率的影像数据,已经成为遥感领域的一种重要技术手段.其中,影像匹配技术是UAV影像数据处理的重要步骤,图像间的匹配直接影响后期三维场景的精度及视觉效果.针对高原山地的高差起伏变化大地形复杂,植被覆被率高及地物分布不规则等问题存在,致使...     

一种无相机标定的立体图像对校正新方法

双目立体视觉是光学被动三维测量的芷要方法。为了快速、准确地寻找对应点,通常要将立体图像对进行校正,消除垂直视差。提出了一种无需标定相机的立体图像对校正方法。该方法从基本矩阵计算初始透视投影、旋转和竖直平移变换矩阵．然后以对应点坐标为基础对这些变换矩阵进行优化计算,从而有效地避免了优化计算的局部最小值,而且不过分依赖基本矩阵的计算精度。通过对提出的方法和完全基于基本矩阵的图像校正方法以及无需基本矩阵计算的图像校正方法进行实验比较,结果表明提出的方法图像校正速度快,能有效地消除垂直视差,而产生的图像变形较小。     

Cryptanalysis of a New Chaotic Image Encryption Technique Based on Multiple Discrete Dynamical Maps

Recently, a new chaotic image encryption technique was proposed based on multiple discrete dynamic maps. The authors claim that the scheme can provide excellent privacy for traditional digital images. However, in order to minimize the computational cost, the encryption scheme adopts one-round encryption and a traditional permutation–diffusion structure. Through cryptanalysis, there is no strong correlation between the key and the plain image, which leads to the collapse of cryptosystem. Based on this, two methods of chosen-plaintext attacks are proposed in this paper. The two methods require 3 pairs and 258 pairs of plain and cipher images, respectively, to break the original encryption system. The simulation results show the effectiveness of the two schemes.     

Illusion optics

The technique of “transformation optics” establishes a correspondence between coordinate transformation and material constitutive parameters. Most of the transformation optics mappings give metamaterials that have graded positive refractive indices that can steer light in curves defined by the coordinate transformation. We will focus on those “folded-geometry mappings” that give negative refractive index materials that have special wave scattering properties. One interesting example is a kind of remote illusion device that can transform the stereoscopic image of an object into the illusion of some other object of our choice. The conceptual device can create the illusion without touching or encircling the object. For any incident wave, the device transforms the scattered waves of the original object into that of the object chosen for illusion outside a virtual boundary. We will illustrate some possible applications of this type of metamaterial remote device, including “cloaking at a distance,” partial cloaking, cloaking from an embedded device, revealing a hidden object inside a container, turning the image of one object into that of another object, and seeing through a wall. The feasibility of building this remote illusion device by metamaterials will also be discussed.     

工业SO2及碳黑颗粒紫外成像遥感监测技术

为了准确有效监测工业烟囱排放,基于SO2及碳黑颗粒物的光学特性,设计并研制出一套双通道紫外成像遥感监测系统.该成像系统的两个光谱通道的中心波长分别定于310 nm和330 nm,利用两个通道的光学厚度之差反演SO2浓度图像,颗粒物浓度图像由330 nm通道获取,根据浓度图像结合光流法获取烟羽运动速度,进而计算得出SO2和碳黑颗粒物的排放速率.结果表明,该工业烟囱的SO2及碳黑颗粒物排放速率分别为72.48±3.16 kg/h和6.33±1.18 kg/h.实验采用紫外相机同时对工业烟囱排放的SO2及碳黑颗粒物进行监测,实验表明双通道紫外成像遥感监测兼具高时间分辨率与高空间分辨率,测量结果准确直观,在工业废气污染、船舶尾气污染以及火山喷发污染排放遥感监测中具有非常明显的技术优势及巨大的应用前景.     

Sensor resolution enhancement for remote imaging by synthesizing mask-based camera array images

In this paper, we propose an architecture based on camera array with masks to enhance the sensor resolution of remote imaging system. The sensor resolution is enhanced by multiplexing the sensor images of each camera, in which the angular resolution bandwidth is converted using masks to expand the spatial resolution bandwidth. The improvement of the sensor resolution depends on the number of cameras in the array. The theory of improving the sensor resolution is discussed both in Fourier domain and spatial domain. We verify resolution enhancement of the architecture by ray-tracing imaging simulation. A simulation model is built to verify the resolution-enhancing ability of the camera array architecture. From each camera in the array, we get a resolution-limited image. The reconstructed image is synthesized from all the images of the cameras. The post-synthesized image has finer information details compared with the images of each camera. The resolution improvement varies with the object distance. The optimal resolution improvement of the reconstructed image is equal to the total sensor pixels of the camera array.     

Glasses-free 3D viewing systems for medical imaging

In this work we show two different glasses-free 3D viewing systems for medical imaging: a stereoscopic system that employs a vertically dispersive holographic screen (VDHS) and a multi-autostereoscopic system, both used to produce 3D MRI/CT images. We describe how to obtain a VDHS in holographic plates optimized for this application, with field of view of 7 cm to each eye and focal length of 25 cm, showing images done with the system. We also describe a multi-autostereoscopic system, presenting how it can generate 3D medical imaging from viewpoints of a MRI or CT image, showing results of a 3D angioresonance image.     

Sphere-based calibration method for trinocular vision sensor

A new method to calibrate a trinocular vision sensor is proposed and two main tasks are finished in this paper, i.e. to determine the transformation matrix between each two cameras and the trifocal tensor of the trinocular vision sensor. A flexible sphere target with several spherical circles is designed. As the isotropy of a sphere, trifocal tensor of the three cameras can be determined exactly from the feature on the sphere target. Then the fundamental matrix between each two cameras can be obtained. Easily, compatible rotation matrix and translation matrix can be deduced base on the singular value decomposition of the fundamental matrix. In our proposed calibration method, image points are not requested one-to-one correspondence. When image points locates in the same feature are obtained, the transformation matrix between each two cameras with the trifocal tensor of trinocular vision sensor can be determined. Experiment results show that the proposed calibration method can obtain precise results, including measurement and matching results. The root mean square error of distance is 0.026 mm with regard to the view field of about 200×200 mm and the feature matching of three images is strict. As a sphere projection is not concerned with its orientation, the calibration method is robust and with an easy operation. Moreover, our calibration method also provides a new approach to obtain the trifocal tensor.     

基于神经网络的视觉系统标定方法

为了解决摄像机标定存在的若干问题 ,根据立体视觉原理 ,提出了基于神经网络的双目视觉系统标定方法。通过对双目摄像机的有效视场分析 ,确定了一次测量面积 ,并把像对视差作为网络输入 ,建立空间点世界坐标与图像坐标非线性映射关系 ,使系统不经过复杂的摄像机内外参数标定 ,就能直接提取物体的三维信息 ,增加了系统的灵活性。实验证明 ,该方法有效可行     

无人机异步图像数据采集系统设计

针对无人机遥感要求高空间分辨率、高光谱分辨率和高时间分辨率且体积小、重量轻,采用离轴三反消像散光学系统满足其大视场轻量化设计要求.提出各相机异步工作,采用单片现场可编程门阵列(FPGA)实现各异步相机数据整合并以同一参考时钟同步实时输出.介绍了整个异步图像数据采集系统的结构,采用FPGA内部的异步先进先出(first in first out, FIFO)实现两路不同时钟域数据按接收端时钟同步输出,在Xilinx ISE7.1环境下用Modelsim6.1进行了时序仿真,并进行了实际测试.实验结果表明:系统稳定可靠,整个成像系统焦距f=70 mm,相对孔径D/f=1/6,视场角2w=65°.采用两组线阵CCD相机工作,总重量仅6 kg.     

X射线三维图象显示

本文介绍的X射线三维图象显示装置是根据双目视差原理,借助于电子学及光学的方法,将不可视的X射线图象转变为可视的立体图象的装置。由两个栅控X射线管构成立体X射线源,采用高灵敏度低惰性的单氧化铅摄象机作为电视摄象系统,通过对电子图象的处理,成功地获得了立体感强、射线剂量低的三维图象。本文在论述立体成象的基本原理之后,着重叙述三维图象立体深度分析法及获得三维图象的处理方法。本装置对于物理、生物医学的研究具有重要的应用价值。 关键词：     

一个评价光谱估计精度的新参数

研究了对多光谱成像系统进行光谱估计的精度评价的问题。在给出光谱估计偏指数定义的基础上,提出了多光谱图像获取系统的光谱估计性能的评价的新方法——系统光谱匹配偏度指数法。该方法用一个指标来定量评价两光谱向量的光谱匹配程度,避免了以往评价参数的复杂性,同时反映了光谱反射率估计曲线实际测量曲线之间的差异程度。采用一典型多光谱相机对Macbeth色卡的24个典型光谱仿真估计所得的24个光谱对数值模拟,验证了光谱反射率估计匹配偏度指数能全面的反映光谱反射率的估计精度的设想;并拿17个多光谱估计系统的仿真估计的光谱数据,计算了它们的系统光谱估计偏度指数,计算结果有很好的一致性。结果还显示,系统光谱估计偏度指数还可用作对多光谱相机光谱估计性能进行等级划分的依据。     

面向地质应用的航空高光谱CASI‐SASI数据大气校正方法对比研究

蚀变信息提取是高光谱遥感地质应用的重要内容。基于特殊吸收峰的蚀变矿物提取是蚀变信息提取的重要手段。由于大气的吸收和散射作用,为了获得更为真实的地物反射光谱,必须进行大气校正。目前,国内外针对大气校正的对比研究主要集中在大气校正前后图像的质量改善、地物分类效果的提升以及校正图像像元光谱与实际地物光谱的相关关系等方面,而对不同校正方法获得的像元光谱与实际光谱吸收峰位的对应情况则很少讨论,这对于依赖吸收峰特征进行蚀变矿物提取的地质遥感极为不利。利用CASI-SASI航空高光谱成像系统,采集了甘肃龙首山地区的航空高光谱遥感数据,并运用ASD光谱仪,对该地区实际地物光谱进行了测量。以此为基础,开展了FLAASH、快速大气校正（QUAC）、经验线（EMPL）等方法大气校正结果的对比研究。通过对比分析,发现FLAASH,QUAC和EMPL均能在一定程度上消除大气的影响,改善航空高光谱遥感的图像质量,但EMPL方法得到的反射率与实际反射率相关性最好。此外,运用人工目视方法开展了实际地物反射光谱的吸收峰位与不同校正方法得到的对应像元反射光谱的吸收峰位的对比研究,发现不同校正方法得到的像元光谱的吸收峰位与实际峰位均存在不同程度的差异,虽然EMPL对吸收峰位的保留效果最好,但依然有“漏峰”的现象。据此,提出运用多种大气校正方法开展综合研究,以提高不同类型的蚀变带定位准确度。