虹膜识别的身份认证系统

基于虹膜识别的身份认证系统包括3部分:虹膜图像采集,虹膜图像预处理,虹膜图像编码和识别。预处理过程中对虹膜的精确定位,使定位后的虹膜图像具有平移、尺度和旋转的不变性。与现有其他方法相比,该方法将Symlets小波用于虹膜图像编码,使算法的运行速度大大提高,为Daugman方法的8倍, 克服了当前流行算法中计算量过大的问题。     

非接触式虹膜图像获取系统的设计

设计出一种非接触式虹膜图像获取系统,由独特的光学结构和图像传输电路构成。系统采用红外线LED照明,在摄像机和图像传感器间加有滤光片以避免杂光干扰,摄像机前加半透半反镜来辅助瞄准;同时采用两个蓝色LED进行辅助照明,蓝光将两个特定的狭缝经凸透镜在人脸上成像,当使用者眼睛到达合适的位置时狭缝成像能够完全重合,从而实现定位,完成非接触虹膜图像获取。图像传输电路采用CMOS图像芯片和专用USB控制器相配合的图像采集传输方案。该虹膜图像获取系统可采集640×480像素的VGA格式图像,采集速度达15帧/秒,不仅满足了虹膜识别技术对图像质量及图像采集速度的要求,而且减小了系统体积并降低了成本。     

基于图像清晰度评价的摄像头辅助调焦系统

提出一种新的图像清晰度(包括锐度和对比度)评价函数,对比传统的图像清晰度评价算法,新算法速度最快且准确,以及和功率谱算法一样优良的灵敏度,适合各种实时自动对焦系统.本文使用一系列不同程度的离焦图片演示了所有算法的性能。同时将新算法应用于一种实际的摄像头模块辅助调焦系统中,系统把采集的每帧图像实时显示在屏幕上,用新算法评价图像的清晰度,从而指导作业员对摄像头模块进行调焦。实践表明该摄像头辅助调焦系统在批量生产摄像头模块时对提高生产效率和稳定质量方面有很大作用。     

一种用于数码视频相机的实时自动聚焦算法

本文针对数码视频相机的噪声大,主体位置不确定性及实时性要求高等特点,详细讨论了传统自动对焦算法的缺陷并提出了一种新的自动对焦算法.该算法采用一种新的可有效抑制高频噪声的对焦量函数--高斯一阶导数(FDOG)来正确评价图像对焦趋势;支持最近主体优先的感兴趣区域自动选择,使得系统可以自动找到主体所在位置进行对焦;结合爬山法,二叉搜索和插值拟合进行对焦搜索,相比传统的两段爬山法,搜索效率提高了40%;通过对聚焦后的图像进行监视,支持视频模式下的动态自动对焦.该算法在一个数码视频相机平台上实现,实验结果验证了算法的优点,适用于高性能数码视频相机.     

千兆网高清双波段视频采集系统

为了实现对远距离目标的实时监控,并全面清晰的捕获目标细节特征,设计了以千兆以太网为数据传输通路,通过FPGA进行采集分辨力切换,同时具有可见及近红外波段独立自动对焦功能的双波段高清视频采集系统。根据监控模式要求,系统将可见光、近红外探测器采集的视频数据,通过FPGA设置为指定分辨力的视频信号,通过千兆网将图像数据传入控制计算机,并由控制计算机进行图像显示与存储、自动对焦等操作。实验表明:系统能够根据监控要求,灵活的进行视频采集分辨力的切换及两路视频的自动对焦,最终实现了在两个波段下通过千兆网对远程目标视频的实时显示和高清存储。     

一种用于数字成像的自动对焦系统

提出一种用于数字成像的自动对焦系统,它以CMOS为图像传感器,用DSP进行数据处理并控制驱动电路调整镜头的位置,达到准确自动对焦的目的。系统采用对焦深度法实现自动对焦,通过改变镜头的位置获得一系列模糊程度不等的图像,计算每幅图像的清晰度评价值构成对焦评价曲线;采用梯度函数作为评价标准来评价图像的清晰度;采用窗口选择技术控制对焦感兴趣范围,减少了数据处理量;对实验样机的测试表明,系统有较好的自动对焦性能,并解决了百叶窗问题,对透过玻璃窗户的目标仍然能正确对焦。     

基于无参考结构清晰度的自适应自动对焦方法

针对自动对焦系统,提出了一种基于单帧图像无参考结构清晰度的自适应变步长爬山搜索策略.该方法利用了无参考结构清晰度可提供的离焦量先验信息:当离焦量大时,大步距粗调快速逼近准焦位置;当离焦量小时,小步距微调准确定位准焦位置.该方法在不降低调焦精度的情况下,大大减少了自动对焦所需的图像数量和决策次数.实际系统实验结果表明,新...     

用Gabor滤波实现虹膜图像纹理编码

针对虹膜纹理的幅度和相位信息特征,利用二维Gabor滤波器族可以很好地模拟皮层简单细胞的二维感受野轮廓,能够最大限度的提供图像局部方向和频率信息的特点,提出一种基于二维Gabor函数族对虹膜图像进行子块分解滤波的改进编码算法。实验结果表明,该方法能有效的提取虹膜纹理特征,从而达到虹膜识别的目的。     

一种新的虹膜识别算法研究

目的 为了提高虹膜识别的速度和可靠性。方法 根据虹膜识别的特征,提出了虹膜自动身份识别的一种新的算法和虹膜像几何畸变的校正方法。结果 用相关系数来测度图像的匹配结果,证实了该算法是有效的。结论 用本文的算法进行的大量抽样实验显示了主这种算法的正确性和可靠性。     

面向直线类目标图像测量的对焦算法

针对直线类边缘图像测量中的对焦问题,文章提出了一种利用被测边缘梯度信息的对焦算法。在包含被测边缘的区域内,该算法计算各行或列中被测边缘点的梯度值,求出这些梯度值的平均值;根据聚焦时边缘梯度相对达到最大的成像特点,将所求得的边缘梯度平均值作为聚焦程度的评价准则。该算法与两种常用对焦算法——灰度差分法和灰度方差法的对比试验表明,在保持平滑性不变的情况下,该算法的单峰幅值比灰度方差法大10倍;它克服了灰度差分法依赖阈值的缺点,而且平滑性明显优于后者,其局部波动平均幅值仅为灰度差分法的1/10。     

倾斜镜面成像的自动调焦方法

倾斜镜面成像系统的像面与光轴倾斜,仅利用轴向自动调焦无法实现像面整体清晰。为此提出一种基于图像清晰度判断的自动调焦方法。该方法将轴向调焦与角度调焦相结合,通过步进方式平移和旋转像接收面,利用离焦函数判断聚焦情况,采用数据拟合回归的方法实现了像面整体清晰。该方法在椭偏成像系统的应用结果验证了其有效性,调焦精度达到微米量级。     

New automated iris image acquisition method

I propose a new iris image acquisition method based on wide- and narrow-view iris cameras. The narrow-view camera has the functionalities of automatic zooming, focusing, panning, and tilting based on the two-dimensional and three-dimensional eye positions detected from the wide- and narrow-view stereo cameras. By using the wide- and narrow-view iris cameras, I compute the user's gaze position, which is used for aligning the X-Y position of the user's eye, and I use the visible-light illuminator for fake-eye detection.     

Self‐Regulating Iris Based on Light‐Actuated Liquid Crystal Elastomer

The iris, found in many animal species, is a biological tissue that can change the aperture (pupil) size to regulate light transmission into the eye in response to varying illumination conditions. The self‐regulation of the eye lies behind its autofocusing ability and large dynamic range, rendering it the ultimate “imaging device” and a continuous source of inspiration in science. In optical imaging devices, adjustable apertures play a vital role as they control the light exposure, the depth of field, and optical aberrations of the systems. Tunable irises demonstrated to date require external control through mechanical actuation, and are not capable of autonomous action in response to changing light intensity without control circuitry. A self‐regulating artificial iris would offer new opportunities for device automation and stabilization. Here, this paper reports the first iris‐like, liquid crystal elastomer device that can perform automatic shape‐adjustment by reacting to the incident light power density. Similar to natural iris, the device closes under increasing light intensity, and upon reaching the minimum pupil size, reduces the light transmission by a factor of seven. The light‐responsive materials design, together with photoalignment‐based control over the molecular orientation, provides a new approach to automatic, self‐regulating optical systems based on soft smart materials.     

An Auto-Focusing Method in a Microscopic Testbed for Optical Discs

An auto-focusing method in a digital image system is demonstrated that uses a standard deviation of pixel gray levels as a feedback signal. In this system, an optical microscope and a charge coupled device (CCD) camera are used to create clear pit images of optical discs. A dynamic focusing scheme is designed in the system-control software, which is able to eliminate environmental disturbances and other noises so that a fast and stable focus can be achieved. The method shows an excellent focusing accuracy. The performance and possible applications of this method are discussed. The test results for optical discs are given in this paper.     

Extending the imaging volume for biometric iris recognition

The use of the human iris as a biometric has recently attracted significant interest in the area of security applications. The need to capture an iris without active user cooperation places demands on the optical system. Unlike a traditional optical design, in which a large imaging volume is traded off for diminished imaging resolution and capacity for collecting light, Wavefront Coded imaging is a computational imaging technology capable of expanding the imaging volume while maintaining an accurate and robust iris identification capability. We apply Wavefront Coded imaging to extend the imaging volume of the iris recognition application.     

基于分辨力空间变化的自动聚焦方法

在获取数字化图象的过程中,快速、有效地实现自动聚焦十分重要。提出一种加快对焦判断的方法,模仿人眼视觉系统中视网膜的空间变化分辨力,建立了模拟模型并进行了数据分析。实验表明,利用所提出的模型,在保持高分辨力的同时又有一个大视场和较少的数据处理量,在保证了为精度的同时又提出了原有的处理速度,在对焦策略上有一定的先进性,在机器人视觉系统和数字成象系统中具有很好的应用前景。     

Acousto-optic tunable filter chromatic aberration analysis and reduction with auto-focus system

An acousto-optic tunable filter (AOTF) displays optical band broadening and sidelobes as a result of the coupling between the acoustic wave and optical waves of different wavelengths. These features were analysed by wave-vector phase matching between the optical and acoustic waves. A crossed-line test board was imaged by an AOTF multi-spectral imaging system, showing image blurring in the direction of diffraction and image sharpness in the orthogonal direction produced by the greater bandwidth and sidelobes in the former direction. Applying the secondary-imaging principle and considering the wavelength-dependent refractive index, focal length varies over the broad wavelength range. An automatic focusing method is therefore proposed for use in AOTF multi-spectral imaging systems. A new method for image-sharpness evaluation, based on improved Structure Similarity Index Measurement (SSIM), is also proposed, based on the characteristics of the AOTF imaging system. Compared with the traditional gradient operator, as same as it, the new evaluation function realized the evaluation between different image quality, thus could achieve the automatic focusing for different multispectral images.