【作者】 宋怀波；

【导师】 路长厚；

【作者基本信息】 山东大学 ， 机械电子工程， 2009， 博士

【摘要】 低质量可见光图像在现实生活中大量存在且应用广泛。但是在许多重要成像领域,很多因素会导致图像的退化、细节部分的丢失,它们会造成图像的混叠,降晰和扭曲。因此观察到的图像往往不能满足实际应用对图像质量的要求。这个特点使得对它们的研究难以直接借用现有的图像处理技术,因而成为光学图像识别中的一个新的研究领域。本文在教育部博士点基金项目资助下,开展了如下研究工作:研究了低质量可见光图像的重建方法。针对低质量可见光图像存在的像素过低、偏斜、旋转以及断裂等不同问题,分别研究了断裂图像的重建技术、图像的填充方法、以及低分辨率可见光图像的超分辨率重建技术。这些图像重建技术的研究是图像特征提取以及识别的前提,具有重要的理论价值和指导作用。提出了基于小区域模板匹配的低质量可见光图像识别方法。现有的模板匹配及其改进算法存在匹配时间过长,不适合工业生产使用的缺点,提出了基于小区域模板匹配的算法原理,并分别对激光刻蚀标牌字符图像和低质量可见光空间目标进行了实验。实验证明该方法可以有效的缩短算法的匹配时间,具有较高的识别率。在此基础上,将相关系数法引入到低质量空间目标的类别识别与姿态识别之中,当测试样本与模板库样本尺寸大小不一时同样可以进行匹配。从实验结果来看,这种基于特征相关系数的匹配方法很适合于空间运动目标的匹配,由于这种匹配方法能够很容易地克服图像中轻微存在的变形、噪声和局部遮挡,因而具有较高的匹配精度。研究了低质量可见光图像的旋转不变性矢量提取方法,解决了样本存在偏斜、旋转等情况时造成识别率下降的问题。首先将矩特征引入到图像的不变性矢量生成之中,给出了具体的算法。然后针对不同旋转下的图像,分别对文中方法和传统方法所提取的矢量曲线进行了对比说明,实验验证了文中方法的有效性。提出了基于概率PCA模型的观测数据集本征维数确定方法。对于观测数据集的主分量确定方法的研究,国内外学者多采用经验式的方法来确定其本征维数,或者直接采用观测数据相关矩阵(或协方差矩阵)中特征值所在总体的方差贡献率大小的方式来定量的得到观测数据集的本征矢量维数。针对这一问题,首先给出了概率PCA模型;然后采用AIC、CAIC和BIC准则给出了本征矢量维数的确定方法;对影响主分量确定的模型的各个参数进行了仿真,并给出了相应的仿真实验结果:对于不同类型的观测样本集,给出了三类准则的适用范围;对提取到的新的特征矢量曲线数据集合,分别用以上三种准则给出了本征矢量维数的确定方法,对于三种准则在字符图像上的适用性给出了说明;最后,采用粗略估计子空间维数区间和精确判定最优本征矢量维数相结合的方法,大大减低了错误出现的可能,提高了算法的鲁棒性,同时也减少了算法的运行时间。对比实验表明,本文提出的方法与传统方法相比具有更高的识别率。提出了基于端点、三叉点和四叉点等结构特征的二级压印凹凸字符识别方法。为了解决统计特征区分相似字符、旋转字符能力弱的问题,建立了基于端点、三叉点和四叉点等结构特征的压印凹凸字符二级识别网络。在第一级基于统计特征识别的基础上采用由三叉点等结构特征组成的第二级识别网络进行识别和校验。实验表明,该二级分类器能够区分相似字符,对于断裂比较严重的字符同样具有很好的识别能力。研究了基于混合Contourlet与主成分变换的低质量图像融合方法。针对低质量图像可能存在的局部遮挡、噪声等问题,将多传感器图像信息或者单摄像机得到的多幅图像信息有机的结合起来,以获取对同一场景的更精确、更全面、更可靠的图像描述。实验表明,采用混合Contourlet与主成分变换的融合方法可以较好的实现目标的融合。本课题为2006年国家教育部博士点基金项目资助课题。更多还原

【Abstract】 There exist large amounts of low-quaility visual images in the real world and they have been used widely. There are many factors which lead to the image blurring, serious detail loss, image warping and ambiguities images, for those reasons, the images we observed are usually not accurate enough to fit the requirement of the image resolution. It is this characteristic that makes it difficult to use the existing research achievements of the traditional optical image recognition to recognize them. Accordingly, recognition of such image becomes a new hot spot. Supported by Doctoral Fund of Ministry of Education of China, the research carried out in this dissertation is as followings.The low-quaility visual image preprocessing is investigated first. Aimed to solve the problem cause by low-resolution, skewed image, rotated image and broken image, the reconstruction of broken characters, filling the holes of image, image enhancement are researched. As the image preprocessing is the precondition of image feature extraction and recognition; such researches paly an important role of theoretical guidance.A novel low-quaility visual image recognition based on the small region template-matching algorithm is presented. It is used to overcome the shortcoming of long time waste and unsuitable for the industrial process. The laser etched label characters and the deep space objects are used to testify the probability of the method, it shows that this algorithm uses less time and could get much higher recognition rate. Based on this method, the theory of correlation factor is lead into the small region template matching method to solve the problem of size mismatching. The experiment shows that this method is suitable for the motion objects; it also shows that this method can easily overcome the deformation, noise and local shading, so this method has much higher matching precision.The rotated image will decrease the recognition rate by using principal component analysis. To solve this problem, a novel sample vector formation method is presented. The invariant features such as moment invariants are used to get the rotate invariant vectors; the recognition is carried out directly on the gray-level images by adopting the improved PCA subspace method. Experimental results show that this method could decrease the number of sieving samples and has much higher recognition rate comparing with the typical method.A central issue in PCA is choosing the number of intrinsic components to retain. However, most studies assume a known dimension or determine it heuristically, though there are a number of model selection criteria in the literature of statistics. In this dissertation, the probabilistic reformulation of PCA is used and a model selection criterion for determining the intrinsic dimensionality of data including Akaike’s information criterion (AIC), the consistent Akaika’s information criterion (CAIC), and the Bayesian inference criterion (BIC) are derived. At last, aimed to the character images, these parameters could affect the determination of the subspace dimension is analyzed in detail. The range of application of these three criterions is analyzed and a two-step method to estimate the intrinsic dimension of the observed character dataset is presented. Experiments demonstrate that the new algorithm is feasible and robust; it also can decrease the time waste. The comparison experiment for the recognition of protuberant characters shows that this method has much higher recognition rate than typical used PCA methods.A new algorithm based on the structural properties such as the endings, the three crossing points, the four crossing points and the positions of the three crossing points is presented. It could solve the problem of low recognition rate caused by rotate, similar and broken characters. A two-level recognition network is setup, the first network is based on the PCA method, after the first step recognition is complete, the result is sent to the second network which is based on the described structural features, the error-prone characters and the character with low degree of confidence are recognized again. Experiment results show that the two-level character recognition network has much higher recognition rate and it is much robust as it can recognize the similar characters and some broken characters.A single sensor cannot produce a complete representation of a scene, Image fusion is the process of combining information from two or more images of a scene into a single composite image that is more informative and is more suitable for visual perception or computer processing. A novel fusion method of low-quality images based on hybrid Contourlet-PCA transform is proposed. The experiment result shows that the proposed method could well fuse hyperspectral images with noises eliminated and it outperforms the Contourlet and PCA methods.This work is supported by Doctoral Fund of Ministry of Education of China.更多还原