二次JPEG压缩对噪音相关性的影响分析

为了探索二次JPEG压缩对数字图像与数码相机的噪音相关性的影响,提高利用噪音相关性鉴别数字图像来源的正确性,降低鉴别过程的复杂性,利用高品质的JPEG格式图像进行JPEG压缩实验,从噪音相关性的分布、噪音相关性的大小、鉴别阈值和错误拒绝率四个角度分析了JPEG压缩对噪音相关性的影响.实验结果表明,JPEG压缩会改变噪音相关性的分布特性,噪音相关性与品质因素是二次曲线关系,当品质因素小于90时,鉴别阈值取平均值,错误拒绝率不会产生明显的误差,从而找到了一种利用噪音相关性鉴别二次JPEG压缩图像来源的新捷径.     

利用相邻相关像素进行噪音抑制的模糊小目标检测算法

提出了一种利用相邻相关像素对红外数字图像中的可疑小目标进行检测的算法. 该算法首先利用自适应全局阈值检测图像中的亮像素,并借助相邻相关像素信息滤除结果中的亮噪音点;然后依据亮像素的相关性,对剩余的亮像素进行加强,并再次抑制噪音,获得可观的信噪比增益.相对于传统的Top-Hat变换,该算法能够在有效提高待检测目标信号强度的同时很好地抑制噪音,有效地保留了目标图像的边缘细节.     

利用相邻相关像素进行噪音抑制的模糊小目标检测算法

提出了一种利用相邻相关像素对红外数字图像中的可疑小目标进行检测的算法.该算法首先利用自适应全局阈值检测图像中的亮像素,并借助相邻相关像素信息滤除结果中的亮噪音点;然后依据亮像素的相关性,对剩余的亮像素进行加强,并再次抑制噪音,获得可观的信噪比增益.相对于传统的Top-Hat变换,该算法能够在有效提高待检测目标信号强度的同时很好地抑制噪音,有效地保留了目标图像的边缘细节.     

辐射图像脉冲去噪方法

为去除辐射图像中的脉冲噪音,建立了一种先进行脉冲噪音检测再进行噪音数据修复的联合去噪音方法.首先采用测地膨胀方法从减灰度图像出发对原图像进行形态学灰度重构,再采用灰度阈值法从原图像与重构图像的差值图像中分割检测出脉冲噪音,然后采用改进非本地均值方法对噪音数据进行修复.改进非本地均值方法对相似像素的选择范围进行了限制,从原理上避免了传统非本地均值方法用于去除辐射图像脉冲噪音时易发生的以错纠错问题,本文对其进行了数学表述.实验证明,该方法对不同类型辐射图像的脉冲噪音均具有较好滤除效果,表现出良好的噪音数据修复和图像细节保护能力.     

辐射图像脉冲去噪方法

为去除辐射图像中的脉冲噪音,建立了一种先进行脉冲噪音检测再进行噪音数据修复的联合去噪音方法.首先采用测地膨胀方法从减灰度图像出发对原图像进行形态学灰度重构,再采用灰度阈值法从原图像与重构图像的差值图像中分割检测出脉冲噪音,然后采用改进非本地均值方法对噪音数据进行修复.改进非本地均值方法对相似像素的选择范围进行了限制,从原理上避免了传统非本地均值方法用于去除辐射图像脉冲噪音时易发生的以错纠错问题,本文对其进行了数学表述.实验证明,该方法对不同类型辐射图像的脉冲噪音均具有较好滤除效果,表现出良好的噪音数据修复和图像细节保护能力.     

基于粗糙集与小波反锐化掩模的图像增强

为了有效去除图像中的干扰噪音,改善模糊不清晰的有用边缘细节信息,提高图像的层次感和清晰度,提出将粗糙集和小波反锐化掩模相结合的方法来实现图像增强.运用粗糙集中的近似及等价属性关系将知识化后的图像划分成不同的区域,再根据估计好的阈值进行数据约简,实现有效去除噪音.运用小波反锐化掩模法对图像的轮廓及细节信息进行增强处理,完成图像的最终增强.实验结果表明,不论在主观的视觉效果上,还是客观的噪音均方误差,该方法的处理结果都是较为理想的.     

基于灰度变换的红外图像实时分割算法

针对高灰度等级红外数字图像提出了一种基于灰度变换的实时分割算法.通过实时分析原始图像中几个小区域的灰度直方图,自动确定分割阈值,将原始图像通过灰度变换实时转换为低灰度等级图像.该算法能够将高灰度等级的红外数字图像实时显示在普通显示器上,并且能够有效抑制背景并保留目标灰度信息.由于变换后的图像灰度等级较低而且背景及噪音信息较弱,极大地提高了红外跟踪器的性能.     

基于混沌粒子群优化的图像Contourlet阈值去噪

提出了基于混沌粒子群优化的图像Contourlet阈值去噪方法.该方法在Contourlet变换域内利用混沌粒子群算法来确定最优阈值,再通过软阈值函数去噪,且不需要噪音方差等先验信息.实验结果表明:该方法与小波Bayeshrink阈值、基于粒子群的小波阈值、Contourlet自适应阈值等去噪方法相比,能有效地去除高斯白噪音和椒盐噪音的混合噪音,提高峰值信噪比,并较好地保留图像的细节和纹理,从而明显地改善了图像的视觉效果.     

基于混沌粒子群优化的图像Contourlet阈值去噪

提出了基于混沌粒子群优化的图像Contourlet阈值去噪方法.该方法在Contourlet变换域内利用混沌粒子群算法来确定最优阈值,再通过软阈值函数去噪,且不需要噪音方差等先验信息.实验结果表明：该方法与小波Bayeshrink阈值、基于粒子群的小波阈值、Contourlet自适应阈值等去噪方法相比,能有效地去除高斯白噪音和椒盐噪音的混合噪音,提高峰值信噪比,并较好地保留图像的细节和纹理,从而明显地改善了图像的视觉效果.     

高光谱成像的水稻螟虫蛀入检测方法

为了控制水稻螟虫预警和喷洒农药用量,实现对水稻螟虫虫害的无损检测,提出了基于主成分分析特征波段检测方法和基于迭代阈值的最优波段检测方法,确定了水稻茎秆螟虫检测的特征波段和最优波段,提取出单波段和组合波段的图像来分割虫孔,从而实现水稻螟虫的精准的无损检测。首先通过高光谱得到的120个样品反射率信息分析确定了光谱区域为450～1 000 nm。基于主成分分析特征波段检测方法,对高光谱图像进行主成分分析,通过前五个主成分图像比较确定第三主成分图像为最佳,然后根据第三主成分图像中各个波段的贡献率来选取特征波长（668.8和750 nm）,最后结合全局阈值分割和图像掩膜等图像处理方法实现对虫孔区域的判别。而利用基于迭代阈值的最优波段检测方法,在可见光波段450～750 nm范围和近红外波段750～1 000 nm范围内应用混合距离挑选最佳的单波段,通过单波段来确定组合波段,对单波段和组合波段进行迭代阈值分割,其中753.5 nm波长分割效果最好,故确定753.5 nm为最优波长,然后提取该波长的图像采用一种基于迭代阈值虫孔提取方法和形态学处理,最后能对水稻茎秆虫孔区域进行判别来实现水稻茎秆虫害是否存在。对60个虫害水稻茎秆和60个正常水稻茎秆进行检测,应用基于主成分分析特征波段检测方法在668.8和750 nm波长处检测率分别为95.8%和93.3%,而应用基于迭代阈值的最优波长检测方法在753.5 nm波长处检测率高达96.7%。说明利用基于迭代阈值的最优波长检测方法对水稻螟虫的检测更加精确,也说明所获取的特征波段和最优波段为以后水稻螟虫虫害的多光谱成像技术提供了理论参考。     

Signal-to-noise ratio evaluation of a CCD camera

A fast signal-to-noise ratio (SNR) digital test method for a CCD camera is presented in this study. The proposed method employs the conventionally used differential operations of two sequential images to determine the noise. However, the technique focuses on two features to improve the SNR evaluation: the noise is separated from the differential image by a specially designed digital high-pass filter that does not affect the noise intensity; and the additional quantization noise introduced into the digital image by the frame grabber is corrected for in the final calculation. The method can produce an objective measurement that offers high repeatability. The results obtained are consistent with those produced by industry standard instruments.     

The use of a consumer grade photo camera in optical-digital correlator for pattern recognition and input scene restoration

In this work an optical-digital correlator for pattern recognition and input scene restoration is described. Main features of the described correlator are portability and ability of multi-element input scenes processing. The correlator consists of a consumer grade digital photo camera with a diffractive optical element (DOE) inserted as a correlation filter. Correlation of an input scene with a reference image recorded on the DOE are provided optically and registered by the digital photo camera for further processing. Using obtained correlation signals and DOE’s point spread function (PSF), one can restore the image of the input scene from the image of correlation signals by digital deconvolution algorithms.The construction of the correlator based on the consumer grade digital photo camera is presented. The software procedure that is necessary for images linearization of correlation signals is described. Experimental results on optical correlation are compared with numerical simulation. The results of images restoration from conventionally and specially processed correlation signals are reported. Quantitative estimations of accuracy of correlation signals as well as restored images of the input scene are presented.     

数字全息周期像的产生机理及在抑制零级衍射上的应用

在数字全息成像中, 利用CCD的RGB模式采样全息图时, 全息重构像会出现特定的周期性分布. 本文从理论和实验上详细研究了这种周期像产生的机理、分布特性和应用. 研究结果显示, 由于CCD的光谱滤镜会使全息图的RGB三个单色采样阵列出现部分像素信号的缺失, 因此, 需要通过特定的demosaicing数学算法对缺失的像素信号进行重建以形成完整的单色采样阵列, 这是数字全息再现像周期分布产生的根源. 而基于demosaicing算法的采样阵列重建会在全息图频谱中引入调制函数, 导致物体再现像和零级衍射斑的周期分布差异. 本文揭示了全息图的RGB采样、demosaicing算法与全息重构像周期性之间的内在关联. 最后, 讨论了结合空间移位和图像形态学技术, 利用重构像的周期性抑制零级衍射斑的应用. 所有理论与实验研究结果完全一致. 关键词： 数字全息 图像周期性 零级斑抑制     

一种测量电视跟踪系统摄像头分辨率的新方法

提出了利用“辐射状分辨率图案”测量电视跟踪系统摄像头分辨率的新方法，它取了“分辨率板法”的优点，避免了目视分辨率板法的缺点。介绍了一种基于图像时空域特征的数字化测试系统。该系统利用图像采集卡实时采集电视跟踪系统摄像头输出的视频图像信号，通过数据和图像处理后计算出摄像头的分辨率。测试过程实现了自动化，试验重复性好，测试结果客观可靠，能够更加合理、准确地反映电视跟踪系统摄像头的成像质量。     

基于外触发和软件控制的多摄像机同步采集处理系统

从硬件和软件两方面对摄像机同步的原理和方法进行了研究,设计并实现了基于外触发和软件控制的多摄像机同步采集和处理系统.提出了通过编程控制将一种通用的数字输出模块作为同步触发信号发生器,并利用Visual C++平台开发了控制程序,能够通过触发信号的周期和波形来调整图像采集频率和摄像机触发电平.设计了软件同步策略,保证多台摄像机之间的图像同步曝光之后能够同步处理.经过验证,所设计的同步采集系统同步精度较高,同步误差小于10 μs,具有设备简单、使用方便、成本低等优点,并且能够消除丢帧、错帧等现象,提供了一种通用的多摄像机同步解决方案.     

Digital image correlation for large deformation applied in Ti alloy compression and tension test

In this paper, digital speckle correlation is used in the measurement of Ti alloy compression and tension test. The key technologies applied in the measurement are discussed in detail, including camera calibration with telephoto lens and digital image correlation in large deformation. Single camera self-calibration algorithm based on photogrammetry is proposed. In the algorithm, the interior parameters of camera are estimated without calibrated object, using the bundle adjustment technique, so the 3-D coordinates of calibration target points are not needed in advance to get a reliable camera calibration result. An updating reference image scheme could be employed to deal with large deformation situation. A large deformation measurement scheme, updating reference image scheme, is proposed in this paper. The un-deformed image is used as reference in correlation at first. Only for extremely large deformation field, in which iteration of correlation is not convergent, the reference image is updated to the image of previous deformed stage. Using this method, not only extremely large deformation can be measured successfully but also the accumulated error could be controlled. The 75 mm lens is calibrated in the measurement and compared the result with extensometer and un-calibrated image. Experimental results show that up to 150% tensile deformation and 50% compression deformation can be measured successfully.     

Two wavelength simultaneous DSPI and DSP for 3D displacement field measurements

A novel optical system is proposed that implements digital speckle pattern interferometry (DSPI) and digital speckle photography (DSP) simultaneously using two wavelength illumination of an object for simultaneous measurement of all three components of the displacement vector field. A collimated red light illuminates both the object and a reference surface in a DSPI configuration which is sensitive to out-of-plane displacement field while a blue light illuminates the object in a DSP configuration which is sensitive to in-plane displacement fields. A color 3-CCD camera records the red and blue lights individually through its red and blue channels, respectively. Two reference images and one image in the deformed state of the object are required for quantitative measurement. Experimental results are presented to validate the system.     

Laser spot location method for a laser pointer interaction application using a diffractive optical element

A diffractive optical element (DOE) is applied to effectively locate a laser pointer spot on a projection screen for laser pointer interaction applications. The DOE is placed in front of a digital web camera to blur the background image while transforming the laser spot into a large diffractive pattern, such as a circle. To calculate the diffractive pattern position on the screen, only a simple subtraction method using two successive digital images with the laser ON and OFF, respectively, is needed. This approach also improves the compressed digital image transmission latency.     

基于序列图像的几何参数测量方法研究

随着测量技术的不断发展,现代工业对物体尺寸检测的准确性及快速性要求越来越高.文中提出了一种利用序列图像来测量物体几何尺寸的方法.使用数码相机获得标定模板的序列图像,通过直接线性变换(DLT)方法来标定相机内部参数,结合透镜成像的知识,对使用数码相机采集到的物体序列图像进行处理和测量,最终计算出物体的宽度和高度.实验证明...