Automatic detection of red lesions in digital color fundus photographs

The robust detection of red lesions in digital color fundus photographs is a critical step in the development of automated screening systems for diabetic retinopathy. In this paper, a novel red lesion detection method is presented based on a hybrid approach, combining prior works by Spencer et al. (1996) and Frame et al. (1998) with two important new contributions. The first contribution is a new red lesion candidate detection system based on pixel classification. Using this technique, vasculature and red lesions are separated from the background of the image. After removal of the connected vasculature the remaining objects are considered possible red lesions. Second, an extensive number of new features are added to those proposed by Spencer-Frame. The detected candidate objects are classified using all features and a k-nearest neighbor classifier. An extensive evaluation was performed on a test set composed of images representative of those normally found in a screening set. When determining whether an image contains red lesions the system achieves a sensitivity of 100% at a specificity of 87%. The method is compared with several different automatic systems and is shown to outperform them all. Performance is close to that of a human expert examining the images for the presence of red lesions.     

颜色相似性度量在主动伪装设计中应用

在充分利用颜色相似性的基础上,提出一种自适应主动伪装设计方案。首先应用结合颜色相似性的K均值聚类获得背景主色,然后根据颜色相似性原则实施目标伪装,最后应用无损数据隐藏技术以实现从伪装图像恢复原图像。实验表明该伪装方案伪装效果好,可有效保护特定军事目标,同时原图像可恢复性使得该方案可应用于数字图像隐蔽通信。     

Segmentation of the optic disc, macula and vascular arch in fundus photographs

An automatic system is presented to find the location of the major anatomical structures in color fundus photographs; the optic disc, the macula, and the vascular arch. These structures are found by fitting a single point-distribution-model to the image, that contains points on each structure. The method can handle optic disc and macula centered images of both the left and the right eye. The system uses a cost function, which is based on a combination of both global and local cues, to find the correct position of the model points. The global terms in the cost function are based on the orientation and width of the vascular pattern in the image. The local term is derived from the image structure around the points of the model. To optimize the fit of the point-distribution-model to an image, a sophisticated combination of optimization processes is proposed which combines optimization in the parameter space of the model and in the image space, where points are moved directly. Experimental results are presented demonstrating that our specific choices for the cost function components and optimization scheme are needed to obtain good results. The system was developed and trained on a set of 500 screening images, and tested on a completely independent set of 500 screening images. In addition to this the system was also tested on a separate set of 100 pathological images. In the screening set it was able to find the vascular arch in 93.2%, the macula in 94.4%, the optic disc location in 98.4% and whether it is dealing with a left or right eye in 100% of all tested cases. For the pathological images test set, this was 77.0%, 92.0%, 94.0%, and 100% respectively.     

窄线宽光纤激光器线宽测量的研究进展

光纤激光器在许多领域都有着重要的应用,随着科技的发展,对光纤激光器线宽的要求也越来越高,因此如何精确地测量激光器的线宽也尤为重要。简要介绍了目前在测量激光器线宽方面的研究进展,着重介绍了几种测量线宽的方法及其原理,对各种方法的优缺点进行了分析。     

彩色数字照相机的设计

提出了一种基于ＣＭＯＳ图像传感器和通用数字信号处理器的低价格、高质量彩色数字照相机的设计方案。介绍了系统的软硬件结构,详细描述了用数字图像处理的方法实现自动聚焦控制、自动曝光控制、ＲＧＢ色彩插值和快速离散余弦变换等关键技术。其设计性能优良,能获取分辨率为１ ０２４×７６８像素的高质量彩色数字照片。     

System optimization in digital color imaging

The work presents an overview of a color imaging system and its elements and then highlights techniques in the literature that attempt to account for system interactions for improved quality or performance. After that, presented in greater detail, are two specific examples of approaches that take into account interactions between elements that are normally treated independently. Finally, concluding remarks are presented.     

DSP utilization in digital color printing

This article discusses the utilization of DSP techniques to digital printing systems, particularly in transforming multidimensional signals from electronic to hardcopy formats by utilizing digital printing solutions and controlling the "marking" engine that is at the heart of the electrophotographic system. Researchers and DSP practitioners are urged to share their vision on the novel use of signal processing algorithms to analyze, manipulate, and solve problems related to high-end digital printing.     

数字视频颜色校正的重要性

根据不同要求，使用应用软件对影像进行颜色校正，在后期制作中十分重要。从颜色属性、拍摄环境和摄像机造成的色差、颜色对视觉的影响和颜色校正等几个方面，叙述了颜色校正的重要性。     

紫外飞秒激光的脉宽测量方法

相对于近红外波段的飞秒激光脉冲，紫外波段的飞秒脉冲由于具有单光子能量高、聚焦特性好、电离率高和成丝阈值低等优点，在高功率密度光场的产生、等离子体光物理等领域有着越来越广阔的应用前景，成为激光技术的研究热点。随着紫外飞秒激光技术的发展，传统的脉宽测量方法不能满足需求。指出了紫外飞秒激光脉宽测量研究的主要进展，讨论了目前可用于紫外飞秒激光脉宽的测量方法，主要有双光子荧光测量法、互相关法、简并四波混频法、多光子电离法，介绍了相关测量原理与特点。在此基础上，对紫外飞秒激光脉宽测量技术研究前景进行了展望。     

In vivo measurement of fundus pulsations by laser interferometry

A new noninvasive interferometric technique is described that yields information about the hemodynamic conditions at the fundus. Typical results as obtained from normal subjects are presented and briefly discussed. There is a typical position-dependent time course of the blood pulse induced dilatation of the fundus tissue.     

Transition ratio of lowpass digital filters

The application of spectral transformations to digital filters has the effect of changing the transition ratio of the original filter. This phenomenon is examined in the letter and closed-form formulas are derived for the lowpass case.     

On the measurement of common-mode rejection ratio

In this brief, several commonly used measurement configurations for common-mode rejection ratio (CMRR) are analyzed and compared with the definition; their advantages and limitations are also discussed. Finally, an improved measurement setup is proposed to characterize CMRR more accurately according to its definition over wider frequency range.     

组合数字彩色动感全息图的研究

提出了一种基于傅里叶变换全息原理制作数字彩色动感全息图的方法。该方法通过获取待记录对象同一时刻不同位置状态和同一位置不同时间状态的多幅图像,将每幅图像分解为RGB三基色灰度图,利用计算机软件编程进行全息编码、记录与模拟再现,再将三基色灰度图合成为彩色图像。将不同位置和不同时刻的再现像按预定方式排列,当人眼移动时由于视觉暂留效应,会看到随着空间状态变化和时间状态变化的彩色动感全息图。实验结果表明,通过该方法制作的全息图能够产生丰富的动感效果,且随着排列规则、角度间隔、时间间隔的变化,动感效果也发生相应变化。     

飞秒激光脉冲宽度测量研究

为了快速准确地测量飞秒激光脉冲宽度,采用二阶自相关方法,设计了用于测量飞秒激光脉冲宽度的测量系统。结果表明,通过自主设计的系统测得800nm种子激光脉冲宽度为217.6fs,而利用Coherent公司生产的单脉冲自相关仪测得脉冲宽度为199.51fs,两者误差仅为0.43%。由此可见,自主设计的测试系统可以对飞秒激光脉冲宽度进行准确测量。     

干涉法测量中的信噪比

本文根据现代随机介质中波的传播理论,从二阶互相干函数出发导出了干涉图信噪比的分析表达式,对不同情况下的结果作了讨论,表明信噪比决定于光束的波长与宽度,传播距离和湍流强度等因素。在一定条件下信噪比将趋向于一个常数,可以用强度起伏的饱和效应来解释这个现象。     

电子航图的颜色校正技术研究

电子航图在飞行仿真领域有着重要应用,然而由于局部纸质航图尺寸、来源及扫描设备等因素的影响,扫描得到的各个子航图颜色不一致,严重影响航图的整体效果.因此本文重点讨论了电子航图的颜色校正问题,利用相郊子航图间的重重叠域,采用线性映射变换的方法,在RGB、YIQ、YUV、HIS 4种颜色空间下对电子航图进行校正和比较.实验结...     

分光法测量LED颜色的不确定度分析

分析了分光法测试发光二极管(LED)颜色的测量不确定度,着重分析了光谱功率分布测量不确定度和波长不确定度对颜色测量的不确定度影响,给出了几种典型LED的分析结果,结果表明,5%的光谱功率分布测量不确定度和0.5 nm的波长不确定度在一般情况下可以满足精度要求为0.001的LED颜色测量.     

Automated measurement system for the investigation of surface state distribution

A semiautomatic measurement system has been developed for studying the interface properties of MOS structures. Software has been developed to control the measurement sequence and to analyse the data. The results which are presented in tabulated and graphical form would be of value for quality control purposes and for detailed investigations of the properties of the oxide-semiconductor interface.     

L波段五位数字移相器的宽带自动修调

以 L 波段五位数字移相器的宽带自动修调为例 ,介绍了激光自动修调系统的组成和工作过程 ,讨论了移相器的可修调设计和修调算法的设计。激光自动修调技术可用于多种微波电路 ,可以缩短调试时间 ,降低生产成本 ,满足大批量生产的要求。