A new method for specular curved surface defect inspection based on reflected pattern integrity

Defect inspection of specular curved surface is a challenging job. Taking steel balls for example, a new method based on reflected pattern integrity recognition is put forward. The specular steel ball surface will totally reflect the patterns when it is placed inside a dome-shaped light source, whose inner wall is modified by patterns with certain regular. Distortion or intermittence of reflected pattern will occur at the defective part, which indicates the pattern has lost its integrity. Based on the integrity analysis of reflected pattern images？ surface defects can be revealed. In this paper, a set of concentric circles are used as the pattern and an image processing algorithm is customized to extract the surface defects. Results show that the proposed method is effective for the specular curved surface defect inspection

Specular reflection based sensing surface deformation of gas tungsten arc weld pool

A sensing system is developed to measure the weld pool boundary and pool suoface deformation in gas tungsten arc welding. LaserStrobe technique is used to eliminate the strong arc light inteoference, and specular reflection from the pool suoface is sensed to describe the relation between the deformed stripes and pool surface depression. Clear images of both the pool boundary and the deformed stripes edges are obtained during gas tungsten arc welding process, which lays foundation for realtime monitoring the pool suoface depression and weld penetration.

Microwave Doppler spectra of sea return at small incidence angles:specular point scattering contribution

It is well known that the sea return echo contains contributions from at least two scattering mechanisms. In addition to the resonant Bragg scattering, the specular point scattering plays an important role as the incidence angle becomes smaller （≥ 20°）. Here, in combination with the Kirchhoff integral equation of scattering field and the stationary phase approximation, analytical expressions for Doppler shift and spectral bandwidth of specular point scattering, which are insensitive to the polarization state, are derived theoretically. For comparison, the simulated results related to the two-scale method （TSM） and the method of moment （MOM） are also presented. It is found that the Doppler shift and the spectral bandwidth given by TSM are insufficient at small incidence angles. However, a comparison between the analytical results and the numerical simulations by MOM in the backscatter configuration shows that our proposed formulas are valid for the specular point scattering case. In this work, the dependences of the predicted results on incidence angle, radar frequency, and wind speed are also discussed. The obtained conclusions seem promising for a better understanding of the Doppler spectra of the specular point scattering fields from time-varying sea surfaces.

MODELING OF LIGHT SPECULAR REFLECTION FROM PLAIN-KNITTED FABRICS: A THREE-DIMENSIONAL ANALYSIS

The paper applies a mathematical model[1] for specular reflection to plain-knitted fabrics by using a three-dimensional analysis. Computer simulation of goniophotometric curves is generated based oa the model. Correction factors are introduced by taking into consideration of geometry of the instrument used. Comparison between the simulated and the measured curves of a straight monofilament yarn with various orientation angles is carried out and reasonable agreement has been obtained.

Comparison between Top and Bottom NiO-pinning Spin Valves: Effect of Interfacial Roughness on Specular Reflection

Top and bottom NiO-pinning spin valves of Si/Ta/NiO/Co/Cu/Co/Ta and Si/Ta/Co/Cu/Co/NiO/Ta were prepared by magnetron sputtering, and X-ray diffraction and giant magnetoresistance （GMR） ratio were measured in the temperature range from 5 to 300 K. For the bottom spin valve, the interracial roughness at NiO/Co is much smaller than that of Co/NiO in the top one. The Co/Cu and Cu/Co interfaces have the same roughness in the bottom and the top spin valves. NiO, Co, and Cu layers have （111） preferred orientations in the top one and random orientations in the bottom one. The GMR ratio of the bottom spin valve is larger than that of the top one at all temperatures and their difference increases with decreasing temperature.

Age-related changes of corneal endothelial cell in healthy Chinese tree shrew measured by non-contact specular microscope

AIM：To determine the impact of age on the morphology of endothelial cells and central corneal thickness（CCT） in Chinese tree shrew.METHODS：One-hundred and twenty eyes of 60 healthy Chinese tree shrews were studied.Based on age,the tree shrews were divided into four groups.After general anesthesia,the images of endothelium were acquired using non-contact specular microscope Topcon 3000 P.Eight parameters of corneal endothelial cells were measured by built-in software,including CCT,endothelial cell density（ECD）,percent hexagonality（HG%）,coeffi cient of variability（CV）,size of minimal cell（Smin）,size of maximal cell（Smax）,average cells size（Savg） and size standard deviation（Ssd）.Data were analyzed using STATA software.The differences of eight parameters among groups and correlations with age were analyzed.RESULTS：In all studied animals,the average CCT was 2 4 9.6 ± 2 .29 μ m（202-301 μm）,ECD was 308 0.72 ± 460.76 cells/mm^2（1239.6-4047.6 cells/mm^2） and CV was 29.10±7.60（13.6-54.6）.CV was significantly different among different groups（P〈0.001）.Strong correlation with age was found in ECD,Smax,Savg,Ssd and CV.CONCLUSION：Cornea of Chinese tree shrews had half CCT of human cornea and similar ECD,CV and size of corneal endothelial cells.Young adult tree shrews had higher ECD,HG% and low CV.ECD,Smax,Savg,Ssd and CV correlated with age signifi cantly.

Performance of Relay Networks in Fading Environments with Dominant Specular Components

Radio propagation in dense and super dense wireless networks as well as indoor-to-outdoor picocell networks can have multiple line-of-sight or multiple specular components. The performance of a dual-hop decode-and-forward relaying system over multiple specular components fading channels(MSCC)with multiple Rayleigh distributed co-channel interferers in an interference-limited environment is investigated. The MSCC fading model is designed to allow direct and meaningful comparisons to be made between line-of-sight channels and non-line-of-sight channels, with exact parameter correspondences. Comparisons of outage and bit error performance between Nakagami-m/Rayleigh and MSCC/Rayleigh fading environments show that the MSCC model is needed to describe line-of-sight channels that cannot be accurately modeled by the Nakagami-m, or other fading models.

Specular Detection and Removal for a Grayscale Image Based on the Markov Random Field

Specular detection and removal has been a hot topic in the field of computer vision. Most of the existing methods are mainly for color images, but grayscale images are widely used. For a single grayscale image with only intensity information, highlight detection and removal becomes a difficult issue. To solve this problem, the single grayscale image highlight detection and removal method based on Markov random field is presented. Each reflection component modeling is estimated by geometric relation of surface normal in diffuse and specular reflection component in the framework of Markov random field. Their maximum a posteriori estimation is calculated under Bayesian formula and highlight area is detected. Finally, image inpainting method based on the BSCB model removes highlights. Experiment reveals that this method can effectively detect grayscale image specular reflection area, improve highlight areas the repair rate.

融合神经辐射场和视觉同时定位与地图构建的混合场景表示方法

目前,传统显式场景表示的同时定位与地图构建(SLAM)系统对场景进行离散化,不适用于连续性场景重建。该文提出一种基于神经辐射场(NeRF)的混合场景表示的深度相机(RGB-D)SLAM系统,利用扩展显式八叉树符号距离函数(SDF)先验粗略表示场景,并通过多分辨率哈希编码以不同细节级别表示场景,实现场景几何的快速初始化,并使场景几何更易于学习。此外,运用外观颜色分解法,结合视图方向将颜色分解为漫反射颜色和镜面反射颜色,实现光照一致性的重建,使得重建结果更加真实。通过在Replica和TUM RGB-D数据集上进行实验,Replica数据集场景重建完成率达到93.65%,相较于Vox-Fusion定位精度,在Replica数据集上平均领先87.50%,在TUM RGB-D数据集上平均领先81.99%。

基于镜面和漫反射面标定板的系统参数标定

为获取同一像素点镜面反射和漫反射两种反射特性的相位信息和标定数据,实现兼具镜面和漫反射面的复合表面物体三维形貌的全场测量,进而扩大测量范围,提出一种基于镜面/漫反射面标定板的系统参数标定方法。设计并制作镜面/漫反射面标定板,该标定板呈棋盘格样式,其表面带有相邻距离已知的标识。基于镜面/漫反射面标定板的特殊构型,通过限位平移的方式,结合外参约束和样条插值算法以融合获取完整参考相位。在同一坐标系下,逐像素标定空间距离、系统参数、像素位置和横向坐标XY间的映射关系。最后,利用完整参考相位和逐像素标定数据重建复合表面物体的三维形貌。实验结果表明:与非全场测量相比,基于镜面和漫反射面标定板的参数标定方法的测量范围扩大了1.5~2倍。该方法在不牺牲精度的同时,实现了非连续复合表面物体三维形貌的全场测量,扩大了测量范围,对复合表面物体的三维形貌测量有实际应用价值。

铝合金反射镜的发展与应用

综述了国内外铝合金反射镜的发展现状,最新应用和技术参数。首先从铝合金反射镜的设计、加工、安装结构和应用4个方面展开论述,然后总结了铝合金反射镜的共同特点和共性技术。最后对铝合金反射镜的应用前景提出了展望。

非直视区域的普通平面镜辅助地面三维激光扫描方法

地面三维激光扫描是获取对象表面几何信息的主要方法之一,扫描对象的完整性是三维激光扫描数据获取的基本要求。为解决实际扫描过程中,因作业空间受限等原因引起的扫描死角而导致点云缺失的问题,本文根据平面镜反射光线原理提出了针对非直视区域的普通平面镜辅助激光扫描数据的获取方法。分析了普通平面镜对激光光束传播路径与距离的影响机理,推导了激光扫描经普通平面镜反射像点对应的物点坐标解算方程;顾及激光扫描特性,设计了包含球标靶和普通平面镜的镜面反射系统,阐述了系统构建、系统检校与系统坐标系构建方法;并通过试验验证了本方法的可行性和精度。

基于黄金分割法的卫星导航信号镜面反射点预测研究

针对利用全球导航卫星系统(GNSS)反射信号进行遥感时镜面反射点位置获取精度低、迭代次数多、计算速度慢的问题,提出了基于黄金分割法预测镜面反射点的预测方法。研究了镜面反射点的特性及其几何关系,通过计算仿真,发现镜面反射点预测是一维单谷凸函数极值搜索问题。将卫星发射机和接收机的位置作为搜索区间,根据黄金分割法的搜索原则插入新的搜索点,依照路径最短原则逐步缩小搜索区间来获取镜面反射点的位置。实验仿真结果表明,所提出的算法具有精度高、反射路径最短、迭代次数少、收敛效率高以及运算速度快的特点。

Corneal endothelial cell density and morphology in low and moderate myopic Chinese eyes

AIM:To describe and compare the corneal endothelial cell density and morphology in young,low and moderate myopic Chinese adults in Malaysian Chinese population.·METHODS:Non-contact specular microscopy(Topcon SP3000P,Tokyo,Japan) was performed in low(n =78;21.22±1.51 years) and moderate(n =78;21.82±1.40 years)myopic subjects.The mean of three consecutive measurements of endothelial cell density(MCD),coefficient of variation(CV) in the cell size,and hexagonal appearance of the cell were obtained.·RESULTS:In low myopic eyes the MCD was 3 063.0±176.2/mm2,the mean CV was 33.4 ±4.0% and the mean hexagonal appearance of the cell was 57.9 ±2.7%.In moderate myopic eyes the MCD was 2961.6 ±159.0/mm2,the mean CV was 33.9 ±3.6% and mean hexagonal appearance of the cell was 56.2 ±4.7%.There were statistically significant differences in MCD(P 【0.000) and hexagonal appearance of the cell(P 【0.005) between low and moderate myopic eyes.·CONCLUSION:The corneal endothelial cell layer in more myopic eyes tends to have less MCD and cell hexagonality compared to lower myopic eyes.Nevertheless,there is no significant difference in CV between low and moderate myopic eyes.

Effect of topical 0.05% cyclosporine A on corneal endothelium in patients with dry eye disease

· AIM: To determine the effect of topical 0.05% cyclosporine A (CsA) on corneal endothelium in patients with dry eye disease. · METHODS: Observational, prospective, case series study. Fifty-five eyes of 29 consecutive patients (9 males and 20 females; median age: 66.8 years, interquartile range: 61 -73.2 years) with moderate -severe dry eye disease were evaluated. All patients were treated with topical 0.05% CsA ophthalmic emulsion twice a day in addition to lubricant eyedrops 5 times a day. The follow- up period was 12 months. Before treatment and at 3 and 12 months post -treatment central corneal specular microscopy was performed. The endothelial cell density (ECD), coefficient of variation of cell size (CoV), and percentage of hexagonal cells (Hex %) were analyzed. ·RESULTS: The median ECDs pre-treatment and at 3 and 12 months post-treatment were 2 352.5/mm 2 (inter- quartile range, 2 178 -2548.5), 2 364/mm 2 (interquartile range, 2 174.25 -2 657.5), and 2 366 cells/mm 2 (inter - quartile range, 2 174.75-2 539.75), respectively (P=0.927, one way ANOVA). The median CoVs pre-treatment and at 3 and 12 months post -treatment were 34.5 (interquartile range, 30 -37), 35 (interquartile range, 30 -38), and 34 (interquartile range, 30.75-38.25), respectively (P=0.7193, one way ANOVA). The median Hex % values pre - treatment and at 3 and 12 months post -treatment were 53 (interquartile range, 47 -58), 54 (interquartile range, 45.75 -59), and 50.5 (interquartile range, 45.75 -58), respectively (P=0.824, one way ANOVA). · CONCLUSION: Treatment of patients with dry eye disease for 12 months with topical 0.05% CsA does not seem to cause substantial changes on corneal endothelium.

基于CCD—镜头耦合的数字X射线成像系统设计与改进

通过分析现有基于CCD—镜头耦合的数字X射线成像系统存在的缺陷,对系统结构进行了改进,对系统部件进行了优化。实验表明,改进后的系统除了获得良好的空间分辨率和检测灵敏度之外,还降低了正向散点噪声对图像的干扰,系统的成像质量得到明显提高。

Altimetric Algorithm and Errors of Ocean Altimetry Using GNSS Reflection Signals

As a new remote sensing technology, the global navigation satellite system（GNSS） reflection signals can be used to collect the information of ocean surface wind, surface roughness and sea surface height. Ocean altimetry based on GNSS reflection technique is of low cost and it is easy to obtain large amounts of data thanks to the global navigation satellite constellation. We can estimate the sea surface height as well as the position of the specular reflection point. This paper focuses on the study of the algorithm to determine the specular reflection point and altimetry equations to estimate the sea surface height over the reflection region. We derive the error equation of sea surface height based on the error propagation theory. Effects of the Doppler shift and the size of the glistening zone on the altimetry are discussed and analyzed at the same time. Finally, we calculate the sea surface height based on the simulated GNSS data within the whole day and verify the sea surface height errors according to the satellite elevation angles. The results show that the sea surface height can reach the precision of 6 cm for elevation angles of 55° to 90°, and the theoretical error and the calculated error are in good agreement.

Changes in endothelial cell density following penetrating keratoplasty and deep anterior lamellar keratoplasty

· AIM: To compare the corneal endothelial cell density (ECD) of clear grafts after penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK). · METHODS: The study included 44 and 54 patients treated with PK and DALK, respectively, between March 2006 and April 2010. Corneal ECD was examined using specular microscopy at postoperative 1, 3, 6, 12, and 18 months, and the values were compared. · RESULTS: Corneal ECD reduction in the PK group was 7.4%, 15.2%, 23.5%, and 28.9% at 3, 6, 12 and 18 months respectively after surgery, compared with 4.2 % in the first month (P <0.01). These figures were 3.0%, 6.7%, 7.2%, and 7.7% at 3, 6, 12 and 18 months respectively, compared with 2.2 % in the first month in the DALK group (P >0.05). · CONCLUSION: Compared with DALK,PK significantly reduced ECD of the clear grafts. These results suggest that survival of endothelial cells in grafts is better after DALK than after PK. ·

Spin transport properties in ferromagnet/superconductor junctions on topological insulator

The spin-dependent Andreev reflection is investigated theoretically by analyzing the electronic transport in a thin-film topological insulator(TI)ferromagnet/superconductor(FM/SC)junction.The tunneling conductance and shot noise are calculated based on the Dirac-Bogoliubov-de Gennes equation and Blonder-Tinkham-Klapwijk theory.It is found that the magnetic gap in ferromagnet can enhance the Andreev retro-reflection but suppress the specular Andreev reflection.The gate potential applied to the electrode on top of superconductor can enhance the two types of reflections.There is a transition between the two types of reflections at which both the tunneling conductance and differential shot noise become zero.These results provide a method to realize and detect experimentally the intra-band specular Andreev reflection in thin film TI-based FM/SC structures.

Reconstruction of Novel Viewpoint Image Using GRNN

A neural statistical approach to the reconstruction of novel viewpoint image us ing general regression neural networks(GRNN) is presented. Different color value will be obtained by watching the same surface point of an object from different viewpoints due to specular reflection, and the difference is related to the pos ition of viewpoint. The relationship between the position of viewpoint and the c olor of image is non linear, neural network is introduced to make curve fitting , where the inputs of neural network are only a few calibrated images with obvio us specular reflection. By training the neural network, network model is obtaine d. By inputing an arbitrary virtual viewpoint to the model, the image of the vir tual viewpoint can be computed. By using the method presented here, novel viewpo int image with photo realistic property can be obtained, especially images with obvious specular reflection can accurately be generated. The method is an image based rendering method, geometric model of the scene and position of lighting are not needed.