应用于虹膜采集装置的自动对焦算法

针对自动虹膜图像采集装置的成像特点,本文提出了一种新的基于对焦深度法的自动对焦算法.该算法根据自动虹膜相机小景深的特点,提出应用图像的ULFM作为清晰度评价函数,并采用粗对焦和精确对焦相结合的二级对焦策略.实际虹膜图像采集系统实验结果表明,算法精度高、鲁棒性强、实时性好,在被摄人距离镜头0.5～2m的情况下,系统都能够准确地拍摄到清晰的可供识别的虹膜图像,一次对焦成功率大于95%.     

径向对称和圆形霍夫相结合的眼睛状态识别

通过分析眼睛状态可以有效地判定出飞行员的疲劳状态.本文提出一种眼睛状态识别的新方法,该方法利用径向对称和圆形霍夫变换相结合识别眼睛状态.根据在睁眼状态下眼睛虹膜呈现径向对称特性,初步判定眼睛状态.对于不能仅用径向对称变换确定眼睛状态的图像,结合径向对称变换定位虹膜中心和圆形霍夫变换定位虹膜中心和半径的方法对眼睛状态进一...     

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.     

适用于虹膜识别的Gabor滤波器参数选择

Gabor变换实现的难点是Gabor滤波器组的参数选择.本文提出了一种适用于虹膜纹理特征提取的Gabor滤波器组参数选择方法.该方法根据图像分块确定Gabor滤波器的位置因子取值;借助海明距离均值曲线确定滤波器尺度因子;通过建立尺度因子与频率调制因子的关系,最终确定频率因子的取值.实验证明,依据该方法设计的滤波器,能有效提取虹膜纹理特征,得到较高识别准确率达到虹膜识别的目的.     

基于形态学算子的睫毛干扰抑制算法

针对虹膜识别中的睫毛干扰抑制问题,本文提出了一种基于形态学算子的睫毛干扰抑制算法.该算法将虹膜图像中的睫毛对象看作是背景图像中存在的随机的,不规则的细微裂缝,通过膨胀算子对这些裂缝进行像素填补,实现了对睫毛干扰的有效抑制.与常见的高斯滤波法相比,所提算法具有更强的睫毛干扰抑制能力.通过CASIA虹膜库的仿真实验表明,所提算法比高斯滤波法消除的睫毛像素点要多40%,可以使Daugman和Wildes定位算法的定位精度分别提高1.7%和2%,定位时间分别减少27.9%和24.2%.     

Optical eye tracking system for noninvasive and automatic monitoring of eye position and movements in radiotherapy treatments of ocular tumors

A noninvasive eye tracking system based on infrared 3-D video-oculographic techniques is proposed for the automatic monitoring of eye position and orientation in external beam radiotherapy of ocular tumors. The presented method can be applied for the real-time estimation of lesion position and tumor-beam misalignments, allowing automatic patient setup and eye movement gated treatments. A prototypal eye tracker was developed and tested on five subjects, achieving gaze estimation errors of 0.5° and eye monitoring frequencies of 125 Hz. The proposed application can potentially improve quality and efficacy of ocular radiotherapy treatments, currently based on invasive, qualitative, and manual control procedures.     

Open-eye detection using iris–sclera pattern analysis for driver drowsiness detection

This paper proposes a novel approach for open-eye detection that can be used in driver drowsiness analysis based on computer vision techniques. The proposed method captures the driver video using a low-resolution camera. The proposed drowsiness detection system has three main stages. The first stage is face detection using elliptical approximation and template matching techniques. In the second stage, the open eye is detected using the proposed iris–sclera pattern analysis method. In the third stage, the drowsiness state of the driver is determined using PERcentage of eye CLOSure (PERCLOS) measure. The entire system is designed to be independent of any specific data sets for face or eye detection. The proposed method for open-eye detection uses basic image processing concepts of morphological and laplacian operations. The proposed system was evaluated with real-life images and videos. Open-eye detection accuracy of 93% was achieved.     

Time-domain optical coherence tomography with digital holographic microscopy

We show that digital holography can be combined easily with optical coherence tomography approach. Varying the reference path length is the means used to acquire a series of holograms at different depths, providing after reconstruction images of slices at different depths in the specimen thanks to the short-coherence length of light source. A metallic object, covered by a 150-microm-thick onion cell, is imaged with high resolution. Applications in ophthalmology are shown: structures of the anterior eye, the cornea, and the iris, are studied on enucleated porcine eyes. Tomographic images of the iris border close to the pupil were obtained 165 microm underneath the eye surface.     

Micromechanics and Advanced Designs for Curved Photodetector Arrays in Hemispherical Electronic‐Eye Cameras

The fabrication of a hemispherical electronic‐eye camera with optimized designs based upon micromechanical analysis is reported. The photodetector arrays combine layouts with multidevice tiles and extended, non‐coplanar interconnects to improve the fill factor and deformability, respectively. Quantitative comparison to micromechanics analysis reveals the key features of these designs. Color images collected with working cameras demonstrate the utility of these approaches.     

Effect of diclofenac on ocular levels of ciprofloxacin and lomefloxacin in rabbits with endophthalmitis

The purpose of this study was to analyze ciprofloxacin and lomefloxacin penetration into the anterior eye tissues after topical instillation in healthy rabbits and with experimental Staphylococcus aureus endophthalmitis. Additionally, effect of diclofenac sodium eye drops on the distribution of both fluoroquinolones in the inflamed eye tissues was investigated. An intense protocol with frequent antibiotic administration was chosen. Samples from aqueous humor were obtained 2 and 6?h after the start of the treatment. Samples from cornea and iris were obtained at the end of the experiment, after euthanasia of the animals. Drug concentrations were measured by HPLC method. The median levels of ciprofloxacin and lomefloxacin in aqueous humor of healthy animals, 2 and 6?h after drug administration were 6.39–9.65 and 5.30–6.81?µg/ml, respectively. Ciprofloxacin levels were neither changed from the inflammation nor after instillation of diclofenac. In contrary, lomefloxacin concentrations in aqueous humour of inflamed eye were significantly increased 12.15–15.08?µg/ml, especially after diclofenac administration (17.12–27.76?µg/ml). Levels of both fluoroquinolones in cornea (13.08?µg/g for ciprofloxacin and 12.25?µg/g for lomefloxacin) and in iris (0.84?µg/g for ciprofloxacin and 1.34?µg/g for lomefloxacin) were higher than MIC and MBC values against S. aureus ATCC 25923. Although higher lomefloxacin concentrations were observed in the aqueous humor after instillation of diclofenac, the levels of both fluoroquinolones in iris and in cornea were not significantly changed. Topical administration of lomefloxacin and diclofenac in combination improved penetration of the antibacterial agent in the aqueous humor which can be of clinical importance.     

基于边缘识别的虹膜定位算法

为了提高虹膜定位算法的抗干扰能力,本文提出了一种基于虹膜边缘识别的虹膜定位算法.该算法应用图像几何矩函数提取虹膜内外边缘的特征,通过由支持向量机(SVM)训练的分类器进行虹膜边缘点的识别.最后由Hough变换对识别的结果进行参数求解并实现虹膜的定位.本算法经过了CASIA虹膜图形库的实验验证,仿真实验数据表明所提算法不仅具有较快的定位速度和较高的定位成功率,而且性能稳定.     

Increasing the information acquisition volume in iris recognition systems

A significant hurdle for the widespread adoption of iris recognition in security applications is that the typically small imaging volume for eye placement results in systems that are not user friendly. Separable cubic phase plates at the lens pupil have been shown to ameliorate this disadvantage by increasing the depth of field. However, these phase masks have limitations on how efficiently they can capture the information-bearing spatial frequencies in iris images. The performance gains in information acquisition that can be achieved by more general, nonseparable phase masks is demonstrated. A detailed design method is presented, and simulations using representative designs allow for performance comparisons.     

Optimal wavelength band clustering for multispectral iris recognition

This work explores the possibility of clustering spectral wavelengths based on the maximum dissimilarity of iris textures. The eventual goal is to determine how many bands of spectral wavelengths will be enough for iris multispectral fusion and to find these bands that will provide higher performance of iris multispectral recognition. A multispectral acquisition system was first designed for imaging the iris at narrow spectral bands in the range of 420 to 940 nm. Next, a set of 60 human iris images that correspond to the right and left eyes of 30 different subjects were acquired for an analysis. Finally, we determined that 3 clusters were enough to represent the 10 feature bands of spectral wavelengths using the agglomerative clustering based on two-dimensional principal component analysis. The experimental results suggest (1) the number, center, and composition of clusters of spectral wavelengths and (2) the higher performance of iris multispectral recognition based on a three wavelengths-bands fusion.     

An Electronic-Calibration Scheme for Logarithmic CMOS Pixels

Logarithmic cameras have the wide dynamic range required to image natural scenes and encode the important contrast information within the scene. However, the images from these cameras are severely degraded by a fixed pattern noise (FPN). Previous attempts to improve the quality of the images from these cameras by removing an additive FPN have led to disappointing results. Using an existing model for the response of logarithmic pixels, it is concluded that the residual FPN in these images is caused by gain variations between pixels. In order to reduce the effects of these variations, a readout circuit, which is based upon a differential amplifier, has been used. However, even with this readout circuit, high-quality images will only be obtained if each image is corrected to remove the effects of both gain and offset variations. Measurement results are presented that show that the quality of the output from the logarithmic pixels is significantly improved if an electronic-calibration procedure is used to correct for both types of variations. In fact, with this procedure, the contrast sensitivity of the logarithmic pixels becomes comparable to that of the human eye over five decades of illumination intensity.     

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。     

基于Morlet小波变换系数的自适应虹膜识别

传统的虹膜识别方法原理复杂,实现困难.为了在保证识别率的同时简化虹膜识别算法,提高虹膜识别效率,本文提出了一种基于Morlet小波变换系数的自适应虹膜识别方法.首先,进行虹膜定位和下眼睑拟合,然后对虹膜图像进行归一化操作,得到512列x64行的矩形虹膜图像,并自适应地确定有效虹膜区域;其次,在虹膜有效区域内,对图像逐行进行一维Morlet小波变换,获得不同尺度下一系列小波变换系数,进而得到不同尺度下的小波变换系数分布图;再次,依据不同尺度下的小波变换系数对图像进行二进制编码,用虹膜代码表示虹膜模式;最后,采用自适应的模式匹配方法对不同的虹膜模式进行分类,给出识别结果.实验证明,该方法可以达到99.946%的识别率,能够满足虹膜识别要求.     

基于多通道Gabor滤波和特征融合的虹膜识别方法

多通道Gabor滤波器提取的虹膜特征具有冗余信息并存在部分非有效特征,针对此问题提出了改进方法。对同尺度不同方向的Gabor特征,利用幅值信息进行融合,对融合后特征进行相位编码,并运用海明距离匹配。这样,既保证了高识别性能,又将虹膜特征码压缩为传统方法的1／2,可提高匹配速度,并节约存储空间。还提出一种虹膜图像质量评价方法,可有效鉴别不适于识别的低质量虹膜图像。在CASIA和UBIRIS虹膜库的实验结果表明该方法是有效的。     

Real-time position and attitude sensing using CCD cameras inmagnetic suspension system applications

A position measurement system using CCD cameras is designed for large-gap magnetic suspension applications. White dots are placed on a magnetically suspended model, which is then scanned by CCD cameras against a black background. A real-time hardware system is applied to detect the coordinates of these white dots and generate corresponding attitude data for the suspended model by the lookup-table method. Circuit hardware is designed and implemented with efficient algorithms to accomplish the objective. The purpose of the real-time measurement system is to detect the position and attitude of the magnetically suspended model and to feed this information to the control circuit. System analysis and test results are presented     

Iris segmentation using an edge detector based on fuzzy sets theory and cellular learning automata

Iris-based biometric systems identify individuals based on the characteristics of their iris, since they are proven to remain unique for a long time. An iris recognition system includes four phases, the most important of which is preprocessing in which the iris segmentation is performed. The accuracy of an iris biometric system critically depends on the segmentation system. In this paper, an iris segmentation system using edge detection techniques and Hough transforms is presented. The newly proposed edge detection system enhances the performance of the segmentation in a way that it performs much more efficiently than the other conventional iris segmentation methods.