归一化算法实现畸变不变图像识别研究

在光电混合联合变换相关器图像识别系统中,对与参考图像完全相同的真目标图像和不同的假目标图像能实现完全识别,但对于与参考图像间存在旋转和比例变化的目标图像却很难识别,甚至无法识别。由此,提出了基于图像质心和最长边的归一化图像处理新算法:根据图像像素总值求取图像质心,根据质心和图像边缘轮廓点之间的长度求出图像的最长边和旋转角度,然后根据统一标准将目标图像和参考图像调整至同一长度和旋转方向的完全相同的图像。最后给出了模拟和实验的相关结果,结果表明,该方法能实现存在旋转和比例变化的图像的畸变不变处理,从而提高了系统的识别能力。     

大孔径静态干涉成像光谱仪图像校正技术

设计了一种基于相位相关与归一化积相关的联合图像校正算法。该算法针对卫星姿态变化对LASIS(大孔径静态干涉成像光谱仪)图像造成的畸变,根据傅里叶变换的旋转平移特性,实现图像序列旋转失真的高精度校正,校正精度达到0.01;同时,基于归一化积相关方法实现图像序列平移失真的校正。针对LASIS数据量大的特点提出了改进的快速自适应模板选取法,使算法的运算复杂度按4n递减。仿真结果表明,该算法能快速有效地校正LASIS图像。     

基于数字微镜器件和旋转螺旋屏的体三维显示系统

研究了一种新型体三维显示系统.利用数字微镜设备(DMD)作为高速空间光调制器(SLM),将三维物体的面片模型经过体素化而获得的螺旋切片序列投射到旋转螺旋屏上,基于视觉暂留效应,按时序高速变化的切片序列被人眼感知为具有真实物理深度的三维图像.重点阐述了基于旋转螺旋屏的成像空间构成方法,分析了基于体立方(BCC)采样策略的体素化方法,设计了针对二值切片图像的DMD 控制算法.实验结果表明,BCC 采样策略减少了40%以上的体显示数据,DMD 的高速响应能力使得原理样机较基于振镜的设计更具显示复杂物体的能力,在500 mm×250 mm 的半圆柱形成像空间内显示的三维图像可以选择任意视点直接观看.     

利用Krawtchouk矩不变量实现基于形状的图像检索

图像在经过平移、旋转和尺度变化后是否仍具有很好的检索效果是基于形状的图像检索研究的一个难点.本文提出了一种利用Krawtchouk矩不变量实现基于形状的图像检索方法.该方法首先对图像进行灰度变换,然后提取图像的低阶矩,取16个低阶矩不变量作为图像的特征向量,并按照相似性度量输出相似图像从而实现基于形状的图像检索.文中给出了实验结果,并与基于几何矩不变量和基于Zernike矩不变量的图像检索方法进行了比较.结果表明本文的方法具有更好的检索性能,和上述两种方法相比,查全率分别提高了21.52%和7.6%,查准率则分别提高了16.25%和6.25%.     

浅论数字印刷中图像可感知色域的构建

随着计算机技术的广泛应用和电子技术的迅速发展,数字印刷技术在近十年得以快速发展。在数字印刷中由于不同媒介的颜色显示和输出原理以及颜色表现能力不同导致媒介色域大小和形状产生差异,在颜色信息的传递过程中难以实现保真再现。本文基于对人类视觉系统模型分析,利用了HVS模型的对比敏感度函数（CSF）在小波变换域中的某些频段实施冗余图像颜色信息的消减。在处理后的图像视觉效果没有明显变化的情况下将特定空间高频冗余信息清除,而低频有效信息被保留,由此可以构建仅表示原始图像中人眼可察觉部分的可感知图像色域。     

基于视点纠正的鱼眼图像场景化漫游方法

针对鱼眼图像畸变大、表示的场景信息不直观等特点,本文提出了一种基于视点纠正的鱼眼图像场景化漫游方法。该方法以鱼眼图像所表示的半球空间为观察对象,通过视点的转移在半球空间进行漫游,以对不同区域内的场景信息进行直观的观察。采用鱼眼图像校正算法为基础建立鱼眼镜头的球面映射模型,通过映射关系对以视点为中心的观察区域进行实时校正,当视点变化时对校正后的可视区域进行实时显示从而实现漫游。实验结果表明,通过本文算法能够实现鱼眼图像所表示半球空间的实时漫游,且漫游时显示的校正图像满足直线约束标准。     

基于前向映射的全景视觉图像解算方法

解算的主要目的是将全方位图像还原成无畸变的图像.本文根据双曲面折反射全景视觉系统成像特点,提出了一种基于前向映射的全方位图像解算的改进算法.该算法首先采用前向映射空间变换方法将全方位图像的像素映射到虚拟观察平面上,然后利用改进的Shepard散乱数据插值法复原完整的解算图像,从而避免了在畸变的全方位图像中直接插值引起的图像解算的失真.实验结果表明,该方法不但消除了全方位图像的非线性畸变,而且提高了插值精度和图像灰度曲面的光滑性,使解算图像更接近真实景象.     

综合PHOG和LWT的图像检索算法

目的研究物体的形状特征在图像描述及图像检索中的区分度和检索性能。方法设计一种综合PHOG形状和提升小波变换的图像检索算法。算法首先对原始图像进行极坐标系方向归一化,提取图像旋转不变特征;其次提取分层图像的PHOG形状特征;然后提取分层图像低频变换系数均值和方差作为提升小波变换特征;最后将各种特征进行融合并用于图像检索,并定义距离衡量公式。结果通过文中设计算法提取的图像形状特征可使各标准测试图像间距离均值为0.2352。结论在Corel图像集上的检索实验结果优于RIM算法和FWTH算法,表明文中算法图像检索领域具有一定的应用前景。     

四边形分片逼近控制点的图像畸变校正算法

针对传统的图像畸变校正算法建模复杂、实时性差且图像信息易丢失等缺点,提出了一种基于四边形分片逼近控制点的图像畸变校正算法.该方法以标准点阵图像作为量测目标,将数学形态学和滑动邻域操作相结合以确定畸变图像像素点质心,采用基于四边形分片逼近的方法来拟合高次多项式校正模型,运用两步一维线性灰度级插值向后映射算法确定输出图像中像素点的灰度.将该算法在TMS320DM6437 DSP上实现,实验结果表明,校正一幅像素为768×494的图像所用的时间为0.036 S,畸变校正的误差在0.31个像素以内,有效地避免了边缘信息丢失、空洞及灰度失真现象.     

基于特征匹配的地图图像自动配准技术研究

本文针对地图中的特征点，提出了一种基于广义特征点的图像自动配准方法，将特征点从单纯的点拓展到特征区域。以Moravec算子结合其他特征约束条件来自动搜索广义特征点。分别对两幅图像提取广义特征点后，利用基于根均方误差和交叉相关的两级匹配算法完成同名控制点的建立。并以局部加权直线拟合方法来校正图像的几何畸变。最后建立两幅图像之间的函数映射关系，完成图像的配准。实验结果证明了该方法的有效性。该方法可用于校正近景面地图影像的几何畸变和遥感图像的局部几何畸变。     

全息图再现象研究

通过分析全息图记录的干涉条纹图样，指出对于二维全息图，一束再现光将产生两个对称于全息图面的物象，两束对称于全息图面的再现光将产生位形相同的物象；三维全息图的再现，象的对称性不变，但原物象的对称再现象有一定的弥散，对称光再现时，等亮度再现象出现在全息图转动一个角度之后，实验上制作了具有清晰透射彩虹全息象的象面反射全息图。     

Zero-order noise suppression with various space-shifting manipulations of reconstructed images in digital holography

In this paper, we describe various numerical space-shifting manipulations of the reconstructed images to remove the dc noise in the reconstruction, in terms of the periodicity characteristics of images in digital holography. The theoretical interpretation on different reconstruction periods of the image and the dc noise is described in detail for the first time, to the best of our knowledge. It is related to CCD sampling periods or frequencies for the fringes and the dc term of a hologram. With the calculations of Hadamard product of two different spatially shifted images and subsequent extraction of the root of it, the dc noise can be suppressed effectively and a clear image with the original intensity contrast can be obtained at the center in the hologram reconstruction, particularly when the image and the dc noise are completely or partially superposed with each other. The experiments for both in-line and off-axis imaging cases show that all results are completely consistent with theoretical predictions.     

Transformation of Reference Spheres by an Aberration Free and Infinitely Large Optical System in the Fresnel Approximation

Imaging of a complex distribution by a thin lens is studied and generalized by analysing the imaging process of a complex distribution defined on an off-axis object sphere in an optical system. First, imaging of an object in an elementary system is considered, and then the considerations for the system being a combination of the elementary systems are presented. The general rule of reference spheres transformation is introduced. It is shown that complex distributions given on an off-axis object sphere are fully reconstructed on an image sphere of the system with a change of scale only. The relations between the parameters of the object and image spheres are determined. Some examples of the applications of the transforming rule are given.     

Symmetry in halo displays and symmetry in halo-making crystals

The relation between the symmetry in halo displays and crystal symmetry is investigated for halo displays that are generated by ensembles of crystals. It is found that, regardless of the symmetry of the constituent crystals, such displays are always left-right (L-R) symmetric if the crystals are formed from the surrounding vapor. L-R symmetry of a halo display implies here that the cross sections for formation of a halo arc on the left-hand side of the solar vertical and its right-hand side mirror image are equal. This property leaves room for two types of halo display only: a full symmetric one (mmm-symmetric), and a partial symmetric one (mm2-symmetric) in which halo constituents lack their counterparts on the other side of the parhelic circle. A partial symmetric display can occur only for point halos. Its occurrence implies that a number of symmetry elements are not present in the shape of the halo-making crystals. These elements are a center of inversion, any rotatory-inversion axis that is parallel to the crystal spin axis P, a mirror plane perpendicular to the P axis, and a twofold rotation axis perpendicular to the P axis. A simple conceptual method is presented to reconstruct possible shapes of the halo-generating crystals from the halos in the display. The method is illustrated in two examples. Halos that may occur on the Saturnian satellite Titan are discussed. The possibilities for the Huygens probe to detect these halos during its descent through the Titan clouds in 2005 are detailed.     

Dependence of reconstructed image characteristics on the observation condition in light-in-flight recording by holography

We analyze the dependence of the reconstructed image characteristic on the observation condition in the light-in-flight recording by holography both theoretically and experimentally. This holography makes it possible to record a propagating light pulse. We have found that the shape of the reconstructed image is changed when the observation position is vertically moved along the hologram plane. The reconstructed image is numerically simulated on the basis of the theory and is experimentally obtained by using a 373 fs pulsed laser. The numerical results agree with the experimental result, and the validity of the theory is verified. Also, experimental results are analyzed and the restoration of the reconstructed image is discussed.     

OLED显示屏表面缺陷自动检测方法

目的 为了解决OLED显示屏表面周期性纹理背景和缺陷边界模糊、对比度低的特征导致其表面缺陷检测困难的问题,开展OLED显示屏表面缺陷自动检测方法研究.方法 对OLED显示屏图像进行奇异值分解,选择前2个较大的奇异值重构图像纹理背景,对原图像和重构图像进行差分运算,获得残差图像.将残差图像像素随机赋予初始隶属度值,采用模糊C均值聚类法获得像素最终隶属度值.根据隶属度大小,将残差图像像素聚成2类,并从残差图像中准确地分割缺陷.结果 选取较大的2个奇异值可以有效地重构OLED显示屏的周期性纹理背景;模糊C均值聚类法分割缺陷获得的区域灰度一致性(U)平均值为0.9846.结论 基于奇异值分解的背景重构方法可以有效地检测OLED显示屏表面缺陷;与分水岭法和Otsu方法相比,模糊C均值聚类可以准确地分割模糊边界的缺陷区域.     

Speckle-noise reduction on kinoform reconstruction using a phase-only spatial light modulator

Random-phase distributions that are statistically independent individually are used for computing kinoforms. These uncorrelated kinoforms are recorded and read out sequentially by a phase-only liquid-crystal spatial light modulator, and reconstructed images with well-developed speckles are added. The fidelity of the resultant image to an original is improved as the number of additions increases. The dependence of the speckle contrast on the initial random phase and the influence of the liquid-crystal spatial light modulator's display performance on the image quality are discussed.     

畸变测量中应用窗口傅里叶变换载频条纹分析

为了测量光学成像系统的径向畸变,提出了基于伸缩窗口傅里叶变换空间载频条纹相位分析的测量新方法.畸变分布测量转化为调制相位测量.首先,将纵向朗奇基准光栅作为模板,通过成像系统成为变形光栅即畸变像.接着采用伸缩窗口傅里叶变换提取畸变载频光栅条纹中心无畸变点的基频和相位信息,获得理想无畸变像的基频成分,然后对变形载频光栅条纹进行频谱分析,滤波提取基频信息、逆傅里叶变换、相位解包,提取径向调制相位分布,计算畸变图像的径向位置畸变分布.最后利用该径向位置畸变分布规律和双线性插值灰度重建对畸变图像进行校正.详细的理论分析和实验结果证明,该方法是可行的.     

Eye rotation and vignetting in visual instruments

The eye can rotate to accommodate the angular position of an object and the distance of the object from it. The rotation of the eye inside its socket to align its visual axis in the direction of an off-axis image may introduce full or partial vignetting when one is looking through a visual instrument with a real exit pupil. We analyze the effects of vignetting owing to rotation of the eye in visual instruments with real exit pupils.     

Three-dimensional shape measurement of large-aperture aspheric mirrors by off-axis null Ronchi test

An off-axis null Ronchi test is presented to measure the three-dimensional (3D) shape of a large-aperture aspheric mirror. The method designs curved fringe patterns as null sinusoidal gratings by means of phase information and ray tracing. In the process of measurement, the curved fringe patterns are displayed on a transmission-type liquid crystal display (T-LCD) screen, and a CCD camera records the fringe patterns containing the information of deviations of the mirror. The slopes of the deviations of the mirror are obtained by using the recorded fringe patterns. The deviations are restored by integrating, and then the 3D shape of the mirror can be reconstructed. Compared with the classical null Ronchi test, the method can provide enough measured data points and avoid the jagged edges of bands on the null gratings. Moreover, the method can conveniently change period and direction of the curved fringes and accurately control phase shifting. Computer simulations and a preliminary experiment are presented to show the performance of the method.